Digital Photography
Understanding Digital Photography
Goals
Camera+Lens+Exposure+Focus+Composition = great images
This class will help you understand your camera, what exposure is, and some rules of composition so
that you can capture the most detail and get the best image your camera is capable of. You will learn to
get as much shadow and highlight detail as possible. Along the way we will explore and learn about how
your digital camera works and how the lens and shutter settings affect your pictures. Terms like F-Stop,
EV, Shutter speed, focal length and others will be explained. We will briefly compare digital photography
to film so we can better appreciate our digital cameras and the old world of film. We will examine how
the automatic features in modern cameras work and when we need to take over. Plenty of time will be
available for questions. The class is informal and time will be spent to help the members understand the
concepts discussed. We will discuss image composition and common types of pictures so you will
understand how to get better pictures. Bring your camera to class. The instructor hopes that you will use
more of the camera controls and leave the restrictions of the camera automatic modes behind as you
explore making better images.
Feel free to ask questions, I want the class to be useful for everybody. Often people won’t ask questions
because they think they are the only ones that don’t understand. That is seldom true!
Bring your own camera. They are all slightly different and we will have some time to experiment and
learn to understand our own cameras better.
I know someone will ask me whether Nikon or Canon or brand X is best. They are all good! You will
notice that professionals mostly use either Nikon or Canon. But Sony, Fuji, Pentax, Olympus, and even
Hasselblad or Leica are fine.
For which computer to use someone will inevitably ask me whether Mac or Windows is best. I try to stay
out of religious questions. I also use both, and can recommend either one! You can even use Linux if you
wish. Even cell phones and tablets can be used for many photo tasks. Adobe Lightroom is available for
tablets and while it isn’t as good as the desktop computer version, it is quite useful.
For serious editing you will need a desktop computer though, and preferably Photoshop or some other
sophisticated image editing package.
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Camera
lens
sensor
file
disc
Editing
Printing
Archiving
indexing
Advantages of Digital over Film
Digital cameras are not just film cameras where the film doesn’t cost anything. There are many
advantages, some obvious, but not all.
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Ok, digital film is basically free. Take lots of pictures, you don’t need to worry about the cost.
This will give you a better chance of getting good images.
It is easy to delete images, in fact I strongly recommend you delete bad/poor images as soon as
possible so nobody sees them. This will enhance your reputation as an amazing photographer.
Metadata stores the date, time, camera settings, and sometimes even the location of the image.
You get to see the image immediately so you can evaluate it.
No nasty chemicals or working in the dark to make images.
Sharing is easy, email, Facebook, blogs, posting, etc. However, note that Instagram and
Snapchat for example do not allow camera photos. You have to use the cell phone camera.
Some big changes are happening to how we take and share photos.
Preserving images is easy, if you remember to back up your files of course!
It is possible to take multiple exposures to increase depth of field or to bracket exposures. This
obviously only works for subjects that don’t move.
You can take multiple exposures that have things moving that you want to get rid of. For
example, a street scene where you want to just show the street, not all the people walking
around. Photoshop can remove the things that don’t show up in all the images.
Why Edit Photos
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Improve colors, contrast, exposure, etc.
Crop to remove extraneous elements that might be distracting or irrelevant.
Straighten and correct tilted or distorted images.
Add or remove objects.
Blur and sharpen parts of the image to focus the viewer.
Add text or other useful items.
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
Correct lens problems.
o Chromatic aberration
o Distortions like pincushion and barrel
Example of serious editing.
Original, notice the clutter on the wall and around the image. There is also a bad color cast.
Colors are fixed, clutter removed, and the candles have even been lit!
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Camera Types
We are going to concentrate on DSLR because of interchangeable lenses, but the principles of exposure,
focus, white balance, and composition apply to all camera types.
Point and Shoot
The simplest dedicated digital camera. These cameras often have a zoom lens, but not always. Light and
easy to use. I think these are disappearing due to cell phone cameras.
DSLR
The Digital SLR (Single Lens Reflex) is the classic film camera updated with digital sensor and controls.
You don’t have to wind the film anymore! The major advantage is the ability to changes lenses, which
means the best control of depth of field and perspective (discussed later). The viewfinder allows you to
see exactly what the lens sees since you are looking through the lens using a mirror and penta-prism
arrangement. This mirror must flip out of the way when the picture is taken so there is always a slight
time lag and this places a limit to how fast pictures can be taken.
DSLR’s almost always include an LCD display that can be used instead of the view finder. This is required
for video capture mode and is useful for some kinds of still photography.
Sales of DSLR’s has dropped a little, but they are still somewhat robust. Big lenses and the image control
they provide is very difficult to replicate in a cell phone camera. The big loser here is the point and shoot
consumer cameras.
I think this market will be there for a long time, people will start with cell phone cameras and then get a
real DSLR when they want to advance their photographic abilities.
Some things will be changing, I hope, they must if they want to keep selling. Touch screen is what people
are used to now. Menus need to be touch friendly. Connections must be available all the time with WiFi.
Batteries should charge without taking them out. Firmware needs to be easily updated. 3rd party apps
should be available, so far Nikon, Canon, Samsung, Sony, Fuji etc. won’t allow other software. Magic
Lantern hacked into the Canon EOS 5D MkII and added all kinds of neat features. Canon is not
cooperating with them.
Phone
Built-in phone cameras have become very sophisticated and are excellent for many situations. They
have a single fixed lens. Zoom is usually digital, which means the number of pixels drops as you zoom to
a longer focal length. The perspective effects of longer lenses is not the same, so there are compromises
in image quality. However, your phone is almost always available, and the panorama and video modes
can be useful. There are add-on lenses available for some models that will expand the capabilities of
your phone camera, mostly for iPhone models. Panorama photos are very easy to create, although
sometimes the extra wide aspect ratio can confuse some image editing and viewing software.
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There are little lenses that can be clipped onto cell phones to add macro, wide, and telephoto. They
don’t equal the quality of DSLR lenses, but they do increase the ability of the cell phone compared to a
DSLR.
Tablet
They work, although I confess I’m not quite used to the idea of people holding up books to take pictures.
And it is annoying if you’re in an audience, they block your view. They also mostly have the same
limitations as cell phone cameras.
Mirrorless
These are a recent innovation, but several companies are marketing them now, Sony and Fuji among
others. They are just like a DSLR except that instead of looking through the lens using a mirror the
viewfinder is instead a tiny digital display, just like a monitor, and there is no mirror. These cameras are
lighter and faster since the mirror doesn’t have to flip up. However, the image is not as “clear” as the
mirrored image would be. I personally don’t think these will be very successful, but we’ll see.
Camera Trends
Most people start with cell phone cameras now, and the serious ones will progress to DSLR’s. I think the
point and shoot ones are disappearing as cell phone cameras get better and better.
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Video
Most if not all cameras are capable of recording video. This class is only about still images so we won’t
cover any of the video features. That is a subject for another class.
Pixels, the digital world
A pixel is a picture element.
It is a little dot that has color and brightness. Our eyes will blend all these dots into an image if there are
enough of them. Newsprint is often about 72dpi, high quality art printing is often 300 or more. Two
terms are in common use, dpi (dots per inch) and ppi (pixels per inch). Beware of marketing, these terms
can be used to obscure printing resolution! There are two kinds, ones that glow and ones that reflect.
Computer screens glow, printed images reflect. This affects how colors are represented and even how
many colors can be displayed. RGB and CMYK.
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There are special cases, the pixel may contain only a luminance value, in fact it is possible to have a pixel
that is only white or black.
Representing colors
Any primary set of colors can be used to create many colors. The primary sets used in digital
photography are different than the ones you learned in school years ago.
RGB
See how the colors blend to create the CMY values?
RGB is used for things that glow. It is also referred to as additive primaries. Monitors, displays, TV’s, etc.
In 8 bit per pixel color (often referred to as 24 bit) (0,0,0) is black while (255,255,255) is white.
Interesting thing about color channels. R mostly has a lot of contrast information, G has a lot of detail,
and B has most of the noise. This is one of the reasons why digital movie special effects have switched
from using blue screen to green screen.
Color wheel
The color wheel is useful for digital photography because it clearly shows the relationships between the
additive and subtractive colors used in printing and on the screen. Your image is too green? You could
subtract some green, but you could also add the opposite color, magenta. Adding a color is the same as
subtracting its opposite, the one 180 degrees away. Understanding the RGB color wheel is very useful
when trying to correct the colors in an image.
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RGB Wheel
See http://blog.asmartbear.com/color-wheels.html for an excellent article on colors.
CMY-K Wheel
CMY, also known as subtractive primaries, is used for things that absorb light, like prints. K, black is
added to make a more solid black because the three primaries are not always exact.
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This wheel shows values in CMYK, used for printing.
Resolution
How many pixels do you need
Well, it depends. Let’s look at some samples.
More pixels does mean better editing possibilities because you can afford to throw some away. Note
also that lenses have a resolution and there is a point where the number of pixels of the sensor doesn’t
really matter. Top lenses are in the 15Mp, but little plastic ones are many times lower.
I am often asked about buying the most megapixels you can. The answer is really that you should buy
the best lenses you can. All cameras have enough pixels now, it is mostly the lens that determines the
image quality and detail. A $300 telephoto does not look as good as a $1200 one. Spend your money on
lenses. You can also wait for the higher resolution camera bodies to get less expensive. Lens design
doesn’t change very often. You can keep your lenses for many years.
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Bit Depth
AKA Color depth, 8 bits allows 256 levels. 16 bits allows 65536. Fewer bits means more chance of visible
banding. It also prevents editing without damage. There is also HDR now with for all intents and
purposes unlimited resolution. The first of these gray samples has 10 levels, the next one has 256.
Sensor
Camera sensors don’t capture pixels, they capture light intensity. By putting little color filters in front
they can capture the intensity of the filtered color. So we obviously need to capture RGB.
Film didn’t work this way, there were actually three layers, each sensitive to a different color.
Bayer (CMOS or CCD)
Here’s what a typical sensor looks like conceptually. Since we have to make the sensor flat (2
dimensions) we have to be a little creative. As you can see this doesn’t really match what we said earlier
about images being made of little colored dots. There are more G than R and B. G was chosen as our
eyes are sensitive to G. Note that this also means there is more detail in the G color channel. This is why
movies use green screening instead of blue screening when using digital cameras.
Map to pixels – demosaicing
Mapping from this to pixels is a bit interesting. Note the special separation of colors, but we need to
combine into pixels at a single point in space with 3 colors.
Foveon
Separate sensor layers, RGB. Very much like film, acts like three layers under each other.
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Dynamic range
The range of dark to light that can be recorded without losing shadow or highlight detail. Blocked
shadows or blown out highlights. This is tied to the bit resolution and the sensitivity of the sensor and
electronics.
Film
Film response to light.
Expose for shadows, develop for highlights. Done by metering shadow and highlight areas.
Digital
Digital is different; photo sensors are pretty much linear in their response to light. They will of course
have a maximum value. At low light levels the real value will also bounce around due to noise.
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The bottom line is that film tolerates over-exposure much better than digital sensors.
Expose for highlights, hope for shadows.
HDR
High dynamic range. Greater than 16 bits. Can be obtained by combining multiple exposures in
Photoshop. Some cameras can do this in the camera, for example the Canon EOS D5. Of course, it must
be compressed before printing, but it allows us to choose what is important in the image.
File formats
Let’s take a look at how digital image files are saved on the computer.
Compression
The amount of data can be reduced by eliminating redundancy. There’s a lot of fancy math involved. If
you want to learn more Wikipedia has articles on the different methods used.
Lossy
JPEG is the most common. It looks at blocks of data. The chrominance (color) and luminance (grayscale
brightness) are treated differently. Truncated cosine series is used.
Non-Lossy
RLE and LZW are common. Run-Length-Encoding looks for repeated strings of data and encodes by just
saving the pattern and how many of them there are. For example, 100 bytes of 0x00 can be saved as
0x64 0x00. Two bytes instead of 100! It isn’t very effective though. LZW is much better, it creates a
dictionary of repeated patterns that can be indexed into. The savings can be quite dramatic.
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Compression can be looked at as entropy squeezers. All the redundancy is removed so only totally
random data is retained.
Container files
A container file is a file that holds a specific kind of image along with information that belongs with it,
known as metadata. It is like a cookie jar with a label that says what the contents are. Examples are JPEG
and TIFF.
Metadata is one of the most wonderful things about digital photography. It keeps exposure information,
image information, location (optional geotags), lens and camera information, and other things.
Metadata is stored in either the file itself or in a “sidecar” file that lives next to the image file. It has the
same root name with a different extension, like XMP. IPTC is the big standard, it holds camera
information, exposure information, copyright, title, etc. EXIF is also widely used. Lightroom handles
metadata elegantly and easily.
BMP
The biggest file format, no compression at all. It simply stores each pixel.
JPG/JPEG
JPG files contain metadata and a JPG encoded image. The metadata has information about color space
and the EXIF and IPTC xml data. IPTC is a standard originally developed for the publishing world, it has
author, title, copyright, and many other useful bits of information. EXIF contains details about the
image. Both are useful.
JPG is a lossy (some information is lost) format, originally developed for sending pictures back from
satellites with limited bandwidth and slow speeds. It separates luminance and chrominance information
and treats them differently. Half of the color information is thrown away. Our eyes are more sensitive to
luminance or brightness. The information is encoded using a truncated cosine series.
Note that the bit depth is 8 bits. Only 256 levels. Typical camera sensors capture at least 10, and as high
as 14. 1024 to 16384.
The white balance setting is “baked in” when the JPEG is created. It can be changed later, but some
image damage will often occur.
JPEG is the worst format for editing. DO NOT EDIT and resave JPG images. This will cause something
known as image rot. Each time the image is saved more information, detail, is lost, and it can NEVER be
recovered.
Note that editing jpegs in Lightroom does not do this. This is because LR does not actually modify the
underlying image, it simply gives instructions on how to modify it before printing or viewing. These
instructions can be changed anytime without affecting the original image. A stroke of genius.
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JFIF
This is a file that contains a JPG and some more information. JPG File Interchange Format. Many
cameras produce these files with the .JPG extension. They are mostly interchangeable with JPG files so
you will probably never know what type it is. You can examine the file hex data to be sure. It will have
JFIF in the beginning.
JPG 2000
A new and improved JPEG standard. It was unfortunately mired in lawsuits so it took a while to become
accepted. It uses wavelet technology. Excellent compression. However, it has never enjoyed widespread
use.
GIF
Pronounced like the peanut butter. Very low color resolution, not suitable for photo quality at all.
Tiff
Tagged image file format. Another container file. Can contain jpg, but usually contains an LZW
compressed image, non-lossy. Owned by Adobe now.
PNG
Portable network graphics, a newer web standard. Lossy or non-lossy.
PSD
The Adobe Photoshop standard. Non-lossy.
Raw
Holds the unprocessed sensor data, not an RGB image file. No loss of data. Sometimes lightly
compressed, depends on the vendor. In a sense, this is probably the best way to store images, but it has
its costs.
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Files are huge.
A special viewer is required, there aren’t any pixels in the file.
However, there are many advantages.
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There is no loss of any detail captured by the camera. The amount of detail you can get out of
the image is maximized. You can even do two or more renderings at different settings to
improve the dynamic range.
As improved de-mosaicing algorithms are developed the images can be improved.
White balance can be changed anytime without losing any detail in the image.
I only shoot RAW, and I strongly recommend it. I only use jpg when I need to upload or email a copy to
someone. All DSLR’s can save images in RAW format. I few point and shoot cameras can, but most don’t.
A very cell phones have started adding the ability to save RAW image files. Samsung S7 does.
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PDF
The Adobe Acrobat standard, portable document format. It can be used for images since jpg and other
formats can be contained in it, but it is best for mixed text and photos.
DNG
Adobe standard release into public domain. A few vendors have used it. Hasselblad. It would be nice to
have only one “raw” data standard. Currently, Canon has a standard, Nikon has a standard, etc.
Why Use Raw Instead of JPEG or Other Formats
If your camera supports a RAW format I strongly recommend that you use it. The RAW contains all of
the original sensor data. Once this data has been translated into JPEG a great deal of image detail is
forever lost. One of the main reasons is the fact that JPEG only has 8 bits (256) levels while the sensor
has at least 10 bits, and often 12 bits now. 10 bits is 1024 and 12 is 4096 levels. When the data is
reduced to fit in 8 bits many pixel values will end up the same even though they were different before.
This data reduction is done in the camera when it is set to save JPEG files. This represents details that
are permanently lost. For example, 3 pixels might 490, 510 and 501. After compression to 8 bits they
might all be 255. After this there is no way to go back. The same thing happens when adjusting
exposure, contrast, or brightness. This means that it is best to do all the editing with at least 16 bits of
pixel resolution. The translation to JPEG should only done into a separate file that is emailed or sent to
the printers. Lightroom or Photoshop have built-in commands to do this output format changing.
Lenses
I’m probably mostly going to use the term lens, but I want to point out that photographers often refer to
the lens as “glass”.
This section will focus on lens focal length (measured in mm) and how it affects images.
History: The very first “lens” was simply a pinhole. It was noticed that a tiny hole could be used to
project an image on a wall.
A magnifying glass is a very simple lens.
Focal Length
This is the distance from the optical center (nodal point) of the lens to the plane where the image is in
focus, or sharp. For a magnifying glass this is the physical center of the lens. If you have ever used a
magnifying glass to start a fire or fry ants, you have found the correct focal length.
F-stop
The ratio between the focal length for the lens in the effective hole through it. This creates a number
that is the same for any lens. This was a stroke of genius, it lets all lens have a common number that
relates to how much light is coming through the lens.
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The F-stop is used to control depth of field as well as how much light comes through the lens. Smaller
numbers mean more light and shorter depth of field.
One thing that you will need to experiment is which F-stop is the sharpest. Even though the depth of
field increases with larger F-stops, you will also find that the overall sharpness starts to decrease. The
best F-stop is usually about two stops from wide open. Experiment to figure it out for your lenses.
A smaller F-stop number is also called a fast lens. The speed of a lens refers to the F-stop.
Depth of field
The range of distance that appears to be sharp. It is actually an illusion caused by the limitation of the
eye resolution. The camera lens is actually only completely focused at one distance. But due the inability
of the eye to see an out of focus spot until it exceeds the “circle of confusion” it will appear sharp at
different distances. Bigger F number gives an apparent increase. Fewer megapixels have an apparently
greater depth of field. So do fuzzier lenses.
Even though DOF increases with the F-Stop, at some point another effect takes place which makes the
image fuzzier again, diffraction. Each lens will have an optimal F-Stop where it is sharpest.
It is also possible to take multiple photos set to different focus distances and combine the sharpness
from each of them to create a large DOF. This is most useful in macro photography. It is supported by
Photoshop and other software packages.
To impress your friends, use the term hyperfocal: it is the focus setting that allows everything from
there to infinity to be in acceptable focus.
For an in depth explanation see https://en.wikipedia.org/wiki/Depth_of_field.
F22
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F8
F4
Bokeh
The shape of the out of focus high-lights. Lenses all differ, depends on the aperture design. Some are
halos, some are doughnuts. Some are just evil distorted shapes that look vaguely like they came from
Mordor. It is affected by lens design and F-Stop.
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F14
F5
Soap bubble bokeh
Lens Resolution
Lens have a resolution limit also. Medium ones maybe around 7 MPixels, really good ones >18 MPixels.
This means we should spend our money on lenses, the sensor isn’t quite so important. Camera
manufacturers needed some kind of number to advertise how good they were so they started the
megapixel race.
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Lens Problems
Chromatic Aberration
This occurs when different colors (wavelengths) focus at different distances. It appears as weird color
fringes around objects mostly away from the center of the image. Zoom lenses are very prone to this
problem at certain settings. Lightroom has a tool that can minimize its effect very nicely.
See the greenish color to the left and the reddish to the right of the branch?
In this image Lightroom minimizes the effect just like magic!
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Distortion
Zoom and wide angle lenses often cause distortions of the flat field. This can also be corrected in
Lightroom.
Fall-off
Some lenses do not transmit light as well on the outside edges so they appear darker. It looks very much
like vignetting.
Converging/Diverging Lines
This is most noticeable when using a wide angle that is not parallel to the scene. It is actually mostly a
function of the using a wide angle lens that is not parallel to the scene.,The effect can be fixed in
Lightroom and other editing software.
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Notice how the building leans backwards and is distorted?
Here it is after a single click adjustment in Lightroom.
Fixing Lens Problems
We’ll cover more of this later, but it is worth mentioning that Lightroom has excellent tools to at least
partially fix these issues. Lightroom even uses the metadata to determine the lens that was used and
Adobe has built a database of corrections for many of the popular lenses for DSLR’s that will
automatically correct many of these issues.
Lens Classifications
Lenses are placed in three categories based on the focal length, normal, wide, and telephoto. The
example numbers used next are based on a traditional 35mm film or a full sized digital sensor of 24 x 36
mm. The rules for other sensor sized will be mentioned later.
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Prime
A prime lens has a fixed focal length. These lenses are usually smaller, sharper, more contrast, and
physically lighter (less heavy).
Zoom
Zoom lenses allow a range of focal lengths, sometimes as great or greater than 10 to 1. They are heavier
than prime lenses, but you might only have to carry one lens with you. However, there is a trade-off in
quality and lens speed. Note that quality lenses are rarely more than 4:1. The higher zooms are less
sharp, have less contrast, and often have chromatic aberration and other image effects.
Digital Zoom
This feature is often advertised as a feature to give wider zoom ranges. It is also the main way that cell
phones can zoom. All that really happens is that fewer pixels of the sensor are used. This gives the
illusion of zooming, but it is actually just throwing pixels away. It has no effect on the depth of field as
optical zoom would. You can also consider this cropping in the camera, something that is better done in
Photoshop later. There is some work being done with real optical zoom for cell phones and we may see
this on cell phones or tablets soon. There are also external zoom lenses that can be added to the cell
phone, but they stick out a lot!
Normal
I normal lens has a focal length of 50mm. This number comes from the diagonal of the expanded square
image, 36mm times the square root of 2. It was decided that this is the view that corresponds to what
our eyes normally “see”. It is of course actually the square root of (362 + 362) which is really
50.91168824543142. 50mm was just a nicer number.
This number actually comes from research about what the eye/brain sees. 46 degrees is called the visual
attention area, the area we mostly concentrate on.
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I strongly recommend that you have a 50mm lens. There are some good reasons for this, especially
compared to a zoom lens.
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Sharp
Constrast
Nice bokeh
Light weight
Low chromatic aberration
low distortion, pin cushion or barrel
Excellent low light performance due to large aperture (small number) F1.4 or better
Shallow depth of field
Moving around gives you good exercise
Wide
A wide-angle lens is one with a focal length less than normal.
Fish-eye
This is really an extremely wide wide-angle, often less than 10mm focal length. Things get really
distorted but this can be used creatively. I’ve never owned one, but I did borrow one once at the
newspaper.
Telephoto
A telephoto lens has a focal length longer than normal.
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Macro or Micro
A lens that can focus really close is called a micro lens by Nikon, and a macro lens by Canon. These are
close-up lenses that let you get really close to the subject.
There are other ways to do macro photography.
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Attaching specialty close-up filter lens in front of a standard lens. This is like being near-sighted
or looking through a magnifying glass.
Using extension rings, tubes or bellows. This lets the lens get further out.
Portrait
A portrait lens is a short telephoto, typically about 75-85mm (for a full frame sensor). This lets the
photographer get a head shot without breathing in the subjects face. It also flattens the nose a little bit,
and allows a shallow depth of field so the background can be blurred.
Specialty Lens
There are some other lenses that don’t fit into the standard categories.
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Tilt/shift. This corrects tilting and skew in the camera. It can also be done in photo editing
software but it never looks completely right.
Lens-baby. A very soft focus lens that can produce some interesting photos.
Effect of Focal Length
Perspective
Long lenses make things look closer together, short lenses make things look farther apart. Normal lenses
make things look just about right!
Depth of Field
Shorter lenses have longer DOF, while longer lenses have shallower DOF.
Lens Attributes
Here is a chart that summarizes lens characteristics that will help you choose the correct lens.
Perspective
Depth of Field
Shake sensitivity
Size
Vertical lines
Wide Angle (short)
Spreads things apart
Deep (long)
Low
Short and wider
Tend to tilt and curve
Normal
Normal
Normal
Normal
Normal
Normal
Telephoto (long)
Makes appear closer
Shallow
High, tripod
Long and often heavy
Tend to stay straight
Lens Features
Auto focus
Some lenses, almost all new ones, have automatic focus. This can be turned off for manual focusing.
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Anti-shake
Some lenses have the ability to reduce any vibration of the camera. This is really important for slower
shutter speeds. It is called VR (vibration reduction) by Nikon and IS (image stabilizer) by Canon. It works
by having a sensor in the camera that can detect motion. This information is then used to vibrate an
element in the middle of the lens that will counteract the shake. Amazing stuff!
Camera shake can also be corrected in the camera body by using pixel shifting and having a larger sensor
with extra pixels all around. These can be used to “shift” the image and make it stable. This works with
any lens, but makes the camera more complicated.
For some lenses it is better to turn the VR/IS off when using a tripod.
Sensor Size Effects
Since the value of “normal” is the diagonal of the squared size of the sensor (using the longest side)
smaller sensors will have a shorter focal length for what is considered a “normal” lens. Another way to
look at this is that a 50mm lens will actually be a telephoto lens if the sensor is smaller than 24x36mm.
Lens Hoods
These prevent bright light from hitting the front element and causing flares and other effects. They also
provide some protection to the lens.
Lens Filters
Various filters used to be important for film, especially slides. The same effects are now easily done in
Photoshop so filters mostly aren’t all that useful with digital photography.
UV
These are often recommended to protect the front element of the lens. They are cheaper to replace
than the lens! They can cause a small amount of image deterioration, so buy a high quality one. For film
they also used to darken the sky a little bit because film was sensitive to UV. I’m not sure that really
matters that much with digital.
Skylight
This filter is designed to darken the sky. It is very useful when doing black and white. The effect can be
duplicated in Photoshop.
Graduated ND (neutral density)
This filter is darker on the top and lighter on the bottom. It is useful for landscapes with a bright sky and
dark mountains.
Warming/Cooling
These are slightly bluish or yellowish colors. They were useful for film, but the effects are easily done in
Photoshop or any editing software.
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Colors
You can add various colors for special effects. This is of course much easier to do in Photoshop. It was
more important in the days of film slides.
Closeup
These let the lens focus closer, basically by making the lens near sighted. They aren’t quite as good as a
real macro lens, but they costs a lot less. They are usually sold in sets of three. You can stack them for
getting even closer.
Polarization
This is very good for getting rid of reflected glare from water and metal objects like car hoods and
fenders. You should have one.
Special Effects
There are some special effects filters, for an example one of them can create stars around bright lights.
Exposure
Exposure refers to the amount of light that each sensor element receives. They are like little buckets
that get filled with light. Too much and they overflow, too little and it is hard to tell how much is in
there, are they damp, moist, soggy or dry? There are three things that are used to control the proper
exposure, ISO (speed), shutter speed, and F-stop.
Ansel Adams zone system
Zone I to X, dark to light. Each one is an F-stop apart (the same as one EV), a doubling or halving in
exposure value.
Correct exposure
This is when the optimal amount of light is collected without losing any detail of interest. The amount of
light is controlled by the F-stop and the shutter speed. The amount of light needed is determined by the
ISO setting. A correct exposure means not over or under exposed. It is a combinations of the correct Fstop, shutter speed and ISO setting. Halving the F-stop lets twice as much light in, but if the shutter
speed is then also halved the correct amount will be received on the sensor.
Setting
ISO
F-stop
Shutter speed
Effect
How much light is needed
Comments
Higher values result in more image noise but let you
use faster shutter speeds and/or slower lenses. Lower
values let you use fill flash outside more effectively.
The amount of light the
Smaller numbers mean more light, but a smaller depth
lens allows to pass
of field. Larger number mean less light and more
depth of field.
How long the shutter lets
Slower shutter speeds mean tripods and moving
light through to the sensor things can blur. Higher speeds can be used to stop
motion.
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The following combinations give the same amount of total light. By choosing one you can optimize
either the shutter speed or the F-stop.




1/125 – F16
1/250 – F8
1/500 – F4
1/1000 – F2
By adjusting the ISO then different combinations can be obtained. If the ISO is doubled then equivalent
values are:




1/125 – F32
1/250 – F16
1/500 – F8
1/1000 – F4
However, remember the tradeoff about higher ISO speeds, the amount of noise in the image will
increase.
Here’s a nice chart showing the relationship of F-Stop and Shutter speed to EV. It also shows how
program mode work by the green lines for a specific model of camera.
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EV values are of more technical interest than being really useful in digital photography. The camera will
tell you if the amount if light is correct. In addition you can examine the histogram result.
ISO
Many years ago, this was known as ASA (now ANSI). DIN was German standard where 100 became 21. In
the 80’s combined into ISO. Roughly shutter speed outside at F8.
EV
Exposure value is a base-2 logarithmic scale defined by Ray (2000, p. 318):
where

N is the relative aperture (f-number)

t is the exposure time (“shutter speed”) in seconds[2]
EV 0 corresponds to an exposure time of 1 s and a relative aperture of f/1.0. If the EV is known, it can be
used to select combinations of exposure time and f-number, as shown in Table 1.
Each increment of 1 in exposure value corresponds to a change of one “step” (or, more commonly, one
“stop”) in exposure, i.e., half as much exposure, either by halving the exposure time or halving the aperture
area, or a combination of such changes. Greater exposure values are appropriate for photography in more
brightly lit situations, or for higher ISO speeds.
For more information see https://en.wikipedia.org/wiki/Exposure_value.
F-Stop
The aperture controls how much light gets through the lens.
Shutter time
Effectively the time that the light is allowed to hit the sensor. Used to either stop motion or to show it.
Puts a limit on how steady you can hold the camera. Inverse focal length rule.
Leaf Shutter
This is a shutter built-in to the lens. Not common today, but was in the past, before SLR’s.
Focal Plane Shutter
Used in DSLR’s. It is an arrangement of two curtains that move in front of the sensor. The first one
opens, then the next ones follows to stop the light again. At higher speeds there will be just a slit that
moves across the sensor. Some curtains move vertically, some horizontally.
Histogram
The histogram is bar graph that shows the count of each brightness value. Black is on the left, white on
the right, and gray in between. Color channels can also be shown by value since each pixel color is
simply a number from 0 to some maximum value. It is a very useful tool and you should learn how to
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use it. You can look at it and get a good idea of what the image looks like. You can also see loss of detail
in both shadows and highlights. The higher the bar the more pixels there are of that color or brightness.
If the bars are all higher on the dark side it means the image is dark, possibly underexposed. If the bars
are higher on the bright side then the image is either light or overexposed. Crowded bars on the dark
indicate lots of dark areas and crowded ones on the light side mean lots of lighter areas. Let’s look at
some examples.
In this image the bright sky causes a bunching of histogram values on the bright side while the ground
values causes a smaller bunching on the dark side.
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Noise
Roughly compares with grain in the film days. Noise is random impulses from the sensors. It is mostly
what is called thermal noise and can be reduced by lowering the temperature. It appears as blue and
purple blotchy areas in images. Do not confuse with chromatic aberration which is a lens defect that
causes color fringing.
Interesting thing about noise, it is mostly constant, depending on the temperature for each sensor.
Chilling the sensor can improve the noise, but it isn’t usually practical. Bigger sensors see more light, so
the ratio of signal to noise gets better. This is why full frame and larger sensors look better. It is also why
too many megapixels degrades the image, each element is smaller and can collect less light, but the
amount of noise is about the same. In the old days of digital we would take a “dark frame”, a picture
with the lens cap on. We could then subtract that image from the real image and it would remove the
noise! Modern cameras have built-in noise reduction that works quite well. Lightroom and other
software packages can also remove the noise. Note that noise is only noticeable at low light levels and in
the darker areas of the image.
Clipping, Blooming, and Color Fringing
Some other digital artifacts that we will see in our images.
-
Clipping is when the sensors are saturated with light, not more detail can be recorded.
Blooming is light values spilling over from overloaded sensor spots.
Color fringing is weird color effects around edges. This is a side-effect of de-mosaicking,
converting the raw pixel information to RGB pixels. It can also be caused by poor lens quality.
Exposure Bracketing
Sometimes you’re not sure what exposure setting is the best. Many cameras can be set to automatically
take several exposures at different settings. You can then later pick the best one or you can combine the
light and dark areas to create an HDR image with amazing dynamic range.
Clipping
This is a new term introduced with digital photography. It refers to the loss of detail when the range of
the sensor is exceeded. In general, avoid, however, artistically it often doesn’t matter. Some rules are to
be broken! I prefer to capture as much detail and range as possible and then make the artistic decisions
later.
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Does it matter here that both shadows and highlights are clipped? Where are the highlights? The
shadows? See any detail? Would it make it better if you could?
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Image types
High key
Not very much dark. A white cat in a snowstorm.
Low key
Not very much light. A black cat in a coalbin.
Camera Controls
Let’s examine the common types of controls that are found on digital cameras.
Metering Modes
This is how the camera decides how much light is in the scene.
Matrix
Uses intelligence to figure out what kind of image this is and then it applies the best exposure setting.
Backlight, flat, light, dark, etc. These are very good now and can be used most of the time.
Center weighted
Looks at the whole image, but pays more attention to the central part.
Average
Looks at the whole scene and averages it.
Spot
Looks at only a small spot in the middle, or sometimes where the focus point it.
Exposure Modes
This is how the camera decides what F-Stop and shutter speed to use for a given amount of light.
SPAM
 Shutter priority – You set shutter speed, camera picks F-Stop.
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


Programmed – Camera tries to pick a good combination of F-Stop and shutter speed. You can
usually choose between various pairs.
Aperture priority – You pick F-Stop, camera picks shutter speed. Some cameras will also set ISO
if speed is too slow. This is my most used setting.
Manual – You pick both. Some cameras will adjust ISO to try and expose correctly. If you also set
ISO to manual, you will have complete control
Auto
Let the smart camera do it for you. Good starting point for learning, but you can often do better with a
little experience.
Scenes
Another form of automatic camera setting that attempts to be smarter by getting some guidelines from
the user as to what kind of photo is being taken. I never use these, but I understand why they were
invented. This class should help you to not need any of them.
Focusing
Most of our cameras will focus at some specific distance. There is a camera that can focus after the
image is taken, but it hasn’t taken over the world yet. It is the light-field or plenoptic camera. See here:
https://en.wikipedia.org/wiki/Light-field_camera . It’s interesting because you can focus on whatever
you want during editing on the computer. It’s almost like magic. But for now, we’ll stick to the
traditional lenses that have to be focused somewhere.
Note that it is almost impossible to see the focus sharpness by looking at that screen on the back of your
camera. Use the zoom image button to really see focus.
Manual
You decide what to focus on and twist the little ring until it is correct. In the past, this was the only way.
It is still useful for difficult subjects.
Automatic
The camera does the focusing for you. This is some amazing technology. Cameras can even focus on
something and if it is moving anticipate where it will be when the image is taken so it can focus ahead of
time on that spot.
The following modes are typical, your camera might have others or different ones.
Spot
This focuses on a single spot, which might be the center or it might be a spot you can move.
Auto
This mode attempts to find the best focus on everything. It usually results in the closest objects being
focused on.
Some Canon models even have a mode that you can focus on two points, and it will select the correct Fstop to keep both in focus. Remember how depth of field works?
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Group
This is like spot, except that the area gets bigger. In other words, it looks for more than one spot to be
focused on that are close together.
Focus modes
Single
In single mode the camera will lock the focus when the shutter button is pressed halfway down.
Continuous
In continuous mode the camera constantly adjusts focus until the image is captured.
Auto
This mode acquires focus when the shutter button is pressed halfway down but if the focus area moves
it will switch to continuous to make sure the subject stays in focus.
White balance
All light sources have a color. Sunlight and shade are different, incandescent and florescent are
different. Our eye/brain system corrects things so they look right. When we see a picture this doesn’t
happen, the colors must be shifted so they appear in their proper relationships to each other. Let’s look
at some examples to see what this looks like.
The original was shot under incandescent lights, it has way too much red/yellow (orange). Subtracting
makes for a much more pleasing image that is closer to what we saw and remember.
Camera Color Modes
Cameras usually have the following modes to deal with color balance. The balance can also be set in
photo editing software afterwards. This is particularly easy with raw images, since the color balance is
not “baked” into the image like it is with jpeg.





Auto, the camera tries to make a good guess. This work on “average” scenes.
Incandescent, cools the otherwise too warm image.
Florescent, corrects for some kind of average florescent, but there are many kinds.
Sun, very consistent.
Shade, tends towards blue from all the sky light.
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
Measured, reads the light from a white or gray card, this is the most accurate, but it takes an
extra step before you take any pictures. I often do this when there is mixed lighting.
One particular challenge is when the light is mixed, sunlight, incandescent, fluorescent and flash all the
mix!
Using a Color Checker
Special cards are available that allow for very accurate color correction.
Variations
There used to be a command in Photoshop that would show color variations.
ISO
Most digital cameras have the ability to adjust the ISO manually or automatically. In addition, the
automatic mode usually has a setting to limit the range, especially the highest ISO that is allowed.
Lighting
Studio
Studio lighting, even for example at a wedding might involve a mix of lights including flash. This is a
subject for another class. We can learn about snoots, barn-doors, honeycombs and many other
interesting contraptions.
Available Light
This is when you do not use a flash but rather use whatever light is there. This is my preferred method.
Flash
Sometimes it is necessary to add some light. It is important to remember that light falls off as the square
of the distance so objects get darker really fast as they get farther from your flash.
Strongly backlit subjects can use fill light. This also works in the night with a brighter background and a
darker foreground.
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When I do need to use flash for more light I use three of them. This gives me more control over where
the light goes.
Another interesting thing is how SLR’s work with flash. When does the light fire?
One curtain opens over the sensor, later a second one covers the sensor. Up to about 1/125 the sensor
is completely exposed, faster speeds the closing one follows the opening one closer and closer. Since the
flash does not last long enough only a part of the image would get the light.
The flash can fire right after the first one opens, or it can fire right before the close happens. If there is
enough ambient light this will affect the image. Moving things can have streaks in front of or behind.
There are some basic flash modes that all cameras have.



Always off
Always on, manual power setting
Automatic, when needed
Most cameras also some additional advanced settings.




+/- compensation
Fill light, usually with a fixed F-Stop, this exposes flash for foreground and then adjusts shutter
to expose background
Use flash to control additional flash units
Fire flash at first curtain opening or second curtain closing, this can provide interesting blurs
Saving Image Files
It is important to keep more than one copy of your image files. Drives fail! This is a major advantage of
digital photography, but many people don’t take advantage of it.
Camera Memory
Some people just store the images on their cameras and buy another card when one fills up. Is this a
good idea?
Internal Drives
Any drive that is built-in to the computer.
External Drives
Any drive that is not built-in to the computer
Hard Drives
Spinning platters. They wear out and can be broken if dropped. MTBF is typically at least 100,000 hours.
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USB Flash Drives
Very effective, large sizes and good prices. They do start to lose data somewhere around 10 years, but
people usually buy bigger ones so in practice this doesn’t mean much.
SSD Drives
A kind of flash drive. No moving parts. But flash memory cells do wear out. These drives are very fast.
Optical Media – CD/DVD/BD
Quality media has a very long life, but recorders are not as common as they used to be. Sizes have not
kept up with other media types. BD is 25GB (very easy to get but you need a BD recorder) to 300GB
(very expensive and not readily available), but a USB flash drive is easily 64GB for less money.
Network Drives
SAN and NAS drives sit on a network. They are very good for automated backup software. Some routers
even have this built-in and will quietly back up your image files as they are changed. Network drives
typically take a little bit more technical savvy to set up, but it is much easier than it used to be.
Cloud Drives
Many to choose from these days. OneDrive, DropBox, iCloud, etc. Remember that you are trusting
someone else to make backups of your valuable images. One cloud supplier didn’t make backups. Their
servers got hacked and all data was lost. The company is no longer in business.
Editing Images
For most images you will edit something to improve the picture.
Cropping
This can get rid of extraneous elements and help focus on the important subject.
Exposure and Contrast
These controls are used to lighten or darken and/or increase the contrast in the image. There are usually
several different controls that do similar things in different ways.




Brightness/Contrast, a blunt instrument, kind of like driving brads with a framing hammer.
Levels, similar, but sometimes works better.
Curves, much better control, but harder to learn.
Shadow, midrange, highlight, etc. These are in Lightroom and others and are very nice to use.
We will look at these controls when we illustrate Lightroom.
Color
Colors can be saturated or desaturated to emphasize something in the image.
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Sharpen and Blur
You might want to make something fuzzy or appear to be sharper. Maybe only part of the image needs
this treatment.
Examples of Editing Images
Almost all image manipulation is a trade-off, some information or detail is lost to improve the overall
image or certain parts of it. BTW, this is another wonderful aspect to the way Lightroom handles images.
None of the changes are actually permanent, more on this later.
Contrast increase
Loses detail, but makes it look better.
Can saturate some values, and spread others so there are holes in the histogram.
The histogram shows a nice even spread. There is lots of detail in the midrange.
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See the gaps in the histogram? This indicates that many color values are missing, loss of detail!
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See how few different values are left? Also notice the bunching at black and white. This shows extreme
loss of detail.
How does sharpening work
Increases contrast around edges, makes it look sharper.
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Noise reduction
Softens the sharpness so the noise can’t be seen as easily. You have to strike a balance between
sharpening and noise reduction. Color and luminance are treated differently. Try Lightroom to illustrate.
Feel free to experiment. Note that 1:1 pixel display makes it easiest to see.
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Taking Better Pictures
Composition
A picture tells a story, lead the viewer’s eye to the reward.
Many techniques for doing this.
A picture tells a story visually. You control the elements to get the viewer to understand the story and
what you are trying to say.
TSCT




Topic – example nature scene
Subject – example a tree
Composition – how we present it, see below
Technique – the mechanics of how we take the picture, exposure and focus
Some of these techniques and composition rules are:
Using Focus
 Selective focus. Use the f-stop to control and the lens focal length. This is where DSLR’s reign
supreme.
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Using light and dark and color
 Vignettes.
 Colors. Bright colors attract the eye, but darker ones can do the same if surrounded with lighter
ones.

Light and dark – using light or dark elements can direct the eye.
Using lines and shapes
 Leading lines, radial or linear.


o Circular – lead the viewers eye to an important element
o Diagonal – direct the viewers eye to something important
Golden mean or rule of thirds – arrange things in a timeless pleasing fashion.
Lines and shapes – use to direct the eye.
Point of View
 Change your point of view, not just eye level, try low and high. Low is often good with children.
Using shutter speed to control motion
 Sharp is not always necessary, even blur of motion can be used. Control the shutter speed.
 Fast shutter speed to freeze motion.
 Slow shutter speed to let things blur.
 Panning to blur background while keeping the subject more or less sharp.
Common mistakes
 Putting the face or any other main object in the middle of the frame. LOOK at the whole picture,
take your time and think about what the image says. Many photographers use tripods not just
to steady the camera but to force them to look carefully at the image.
 Trying to cram too much into a picture. Simplify. Get closer. Look at great photographs.
 Color or contrast issues can be distracting.
 Improper exposure. Use the F-stop, shutter speed and ISO correctly.
Sports
Sometimes use shutter speed priority to freeze motion, but not always. Long lens are typically required.
Be prepared to spend lots of money. You need long and fast lenses.
Show Movement
Panning can be used. Slow shutter will let things that move become blurred.
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Water
Using a slow shutter speed lets the water look smooth. A tripod is required.
Night
The extreme contrast range makes night photography challenging. Multiple exposures and HDR can help
by combining highlights and shadows from different exposures.
Landscapes
You need foreground, background, and middle ground.
Where do you put the horizon? Not in the middle!
Forests
Avoid the ground, it is often cluttered.
Flowers
Who doesn’t like flowers? Try different angles. Blur the background or put something behind the flower
to get rid of distractions in the image. Backlighting is often good. Carry a spray bottle to put some
droplets on the blossoms. Get close.
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People
Eyes in focus. It is often good to catch people doing things in their environment. Sometimes need fill
flash or reflectors to get some light on the face.
Pets and Animals
Focus the eyes. Leave room in the frame for them to escape so they aren’t held captive.
Of course rules are sometimes made to be broken. Images don’t have to be sharp to be interesting.
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Children
Get down to their level so you don’t look down at them.
Sunset/sunrise
Silhouettes are always a good idea. Also a little warming and under exposure makes the sky look better.
Different angles
Try and find a different angle to make things look more interesting. Walk around, take some time to look
at things from different locations.
Backlight
This can be used for silhouettes or for seeing light through semi-transparent things. It is often beautiful
for flowers.
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Macro – get really close
Use either macro/micro lenses or extension tubes or close-up lenses.
Government Buildings
No, not a good idea these days. Especially not military installations!
Travel
Look around for something that hasn’t already been photographed by everybody. Some good tips are
available at http://photosecrets.com/ . They sell books these books of tips, not free.
Publications
Look at what kinds of images are published. Magazines, newspapers, travel books, posters, and other
places. This will give you some idea of what kinds of images are popular, although it may not be what
you want to do, it will give you some ideas on how to crop, adjust color, select subjects, and other
things.
References
Books – check Amazon, many are even on Kindle.
Web – Vast amounts of information are available on the web now.
Software
There are many programs out there to manage and edit your collection. We can’t even begin to cover all
of them. We will spend a little time with LightRoom in this class.
Tagging Images
Tagging or adding keywords to images is a great tool for finding items as your collection grows. The tag
words are actually stored as metadata that is attached to the image files. Popular ways of organizing
images in the past were:

Dated folders
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
Named folders showing subject or location
Neither of these methods are very good. You might not remember when a photo was taken. If your
image contains trees, water, flowers, and clouds, what named folder do you store it in?
By using keywords to tag your photo you could put trees, water, flowers, and clouds and the image
would show up when you search for any of those terms. This approach also allows the photos to be
stored off-line but still be searchable.
Google Photos
This is the replacement for Picasa which was left for dead March 2016. It is very good. Among other
features it can recognize faces and objects so that you can search for people and things. It does this
automatically so you don’t have to manually attach keywords (tags) to images. I tried searching for
“tractor” and “flowers”, it worked in both cases. It also has a reasonable set of editing tools. It is not as
feature rich for editing and metadata, but is more than adequate for most people. It synchronizes nicely
across your phone and computers. Phone pictures are automatic. You need to upload photos from other
cameras. Give it a try.
ACDSee
I interviewed with them many years ago up in Victoria BC. It’s a good product, but seems to be
struggling to get noticed. However, it is very good. It has many Lightroom like features.
Corel PaintShop Pro
This has been the perpetual attempt to unseat Photoshop. It is also quite good.
Aperture
Apples competition for Lightroom. Only runs on OSX, but is excellent.
Lightroom
I was a beta tester many years ago. Lightroom is one of the best programs for a digital photographer to
use. It manages most of the important tasks in digital photography. It even runs on both OSX and
Windows.
One of the major advantages of using LR is that the original image files are NEVER modified. You can
crop, change colors, sharpen, reduce noise, tilt, and do many things to the image. You can then hit the
reset button and the original image will be restored. This can even be done after quitting LR and starting
again. You can even make virtual copies of an image and try different treatments on them. These copies
only take a tiny amount of space on your disc since they are not actual copies of the image, they are
simply a control file listing the changes made to the image. You can even save the changes and apply the
same thing to different images. Any number of images can be compared right on the screen so you see
what they look like together. This is a great stuff!
LR lets you browse thumbnails of your images while the original files are offline, that is, on backup
media that is not currently connected. LR has its operations separated into logical modules.
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







The import images module is used to get the images from your camera onto your computer. It
lets you add some keywords and decide where to put your files.
Gallery view lets you visually explore your collection.
Develop view is used to make image changes.
Map view shows you where your images were taken, but you need geotags of course.
Book can create photo books with text and many customizable layouts. The output can be a PDF
or it can be sent to a book publisher.
Slideshow is obviously used to build slideshows. They are pretty simple, but make a nice PDF
file.
Print is where you build images for printing. It lets you add titles, multiple pictures, and other
useful things.
Web is for building web sites.
Adobe Bridge
This is a replacement for Windows Explorer of OSX Finder that is oriented visually. It also deals nicely
with displaying, browsing, and searching metadata and other file attributes. It is included with the
Photoshop/Lightroom subscription.
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Digital Printing
Test Images
There are many test images available for printing, you can of course also make your own. Here’s one of
the classics.
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This is one I use for printer color calibration.
Image Pixels
How many pixels do we need and how big can we print? First note that the image file does not have any
notion about how big it should be printed. It is simply a collection of pixels. In order to print we will need
to assign a ratio of pixels to inches. Considering the resolution of the human eye and the “normal”
viewing distance of about 1.5 to 2 times the print diagonal we come to resolution of around 300 ppi at a
viewing distance of about 2 feet for an 8 x 10 ish photo. Some printers work nicely at 300 and others
prefer 360. I’ll skip the math, but this has to do with the resolution of the eye, which is around ½ minute
of arc.
For some photos the 1.5 viewing distance is not ideal, panoramas are an example. You want the viewers
eye to wander around the image.
As an example, if you want an 8 x 10 print you’ll need a minimum of 2400 x 3000 pixels. The viewing
distance should be about 20 inches. This not a hard and fast rule, you can make acceptable images with
fewer pixels. For a 16 x 20 you would have 4800 x 6000. This is a 28.8 MPixel image. However, we can
create more pixels in most software, this doesn’t really create any more detail in the image, just more
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pixels. Now to make this more confusing, we should be viewing this from farther away, so we could
really print at something less than 300 ppi.
If your image had only 1200 x 1500 pixels but you wanted to have 2400 x 3000 Photoshop and probably
all image editing software will have tools to increase the number of pixels. This is called uprezzing. This
technique does create more pixels but note that it does not, in fact cannot, create more detail in your
image. For example, if there was a button that only occupied a single pixel in the original, you won’t be
able to see the button holes no matter how many pixels you create. Magic does not apply. That’s why
it’s so funny to watch TV and movies shows where they zoom in on a license plate and can see every
little detail when they started from a fuzzy VHS tape.
For more details see:
https://photo.stackexchange.com/questions/17835/how-to-calculate-viewing-distance-for-a-print-size
and
http://www.northlight-images.co.uk/what-print-resolution-works-for-what-viewing-distance/
Viewing Distance (inches)
Resolution ppi
6
1145
10
687
24
286
36
191
60
115
120
57
600
11
The formula is ppi = 1/((distance x 0.000291) / 2)
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Factors for how many pixels we really need
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Viewing distance
Image size
Artistic intent
Paper type
Contrast
Visual acuity of the viewer
Lighting level
Printer DPI and PPI
There are two numbers that are interesting. Printer manufacturers like to keep this obfuscated so they
can get you to believe that their printer is many times better than the other ones. Nearly all inkjets do a
decent job of printing. The high-end Glicee printers are better, but it comes at a cost.
PPI is pixels per inch and is also known as the rendering density.
Within each pixel the printer can put many little dots in order to create the correct color. This number is
measured in DPI, dots per inch.
Printer boxes would show either number. Some printer manufacturers like to show the DPI since it is a
much larger number which can be used as a sales tool.
Here is a good site if you really want to know more details about this works.
http://www.rags-int-inc.com/PhotoTechStuff/Epson2200/
Printing these tiny dots inside a pixel often uses a technique called dithering. Dye-sub printers don’t
need to do this because the colors flow together. Some HP printers use steam and this also causes some
blending. Epson uses piezo-electric so no blending takes place. That is one of the reasons Epson always
show such incredibly high DPI numbers.
Bottom Line: you seldom need to print more than 300 PPI, and often less is enough. It all depends on
how far away you view the image.
Gamut
This measures how big a color range can actually be printed. The gamut of printing is much less than
that of a display, so don’t expect your prints to look as good on paper.
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The gamut of Glicee printers is much larger than that of CMYK printers. My HP Z3100 has 7 colors and
three shades of gray. Each in their own ink tank.
Printing Accurate Color
So how do you get the colors you see on the screen to match exactly what ends up on the print? This is a
complex subject that is beyond this class. But a few general concepts can be discussed.
The solution is called color management and works by having calibrated monitors and printers. There
are devices available that can calibrate monitors to a known standard so the light color is guaranteed for
the values stored in the image file. I think this uses .ICM files.
Printers can also be calibrated so they print known colors for specified values. These are .ICC files and
must be created for each set of ink and paper. There are tools to create these profile files, but many
printer manufacturers provide sample profile files, at least for their own papers. Note that using OEM
inks will usually never match these profiles.
Most printers have profiles available for their paper and printers. Costco profiles can be downloaded
from www.drycreekphoto.com.
Both Lightroom and Photoshop can be set to display the image using the specified printing profile. This
will give you some idea of what the print will look like. This is called soft proofing in Lightroom and is a
checkbox in the develop module. Since the gamut of a printer is never as great as that of a monitor it
will never be possible to see exactly the same on the monitor as on the printer output. Photoshop and
other professional software has “soft proofing” available that will map the monitor image so it matches
the printer profile (ICC) file in use. Be warned that this always looks a bit “flat”, but that is the nature of
printing as compared to glowing monitor screens.
If you don’t want to bother with the finer details of printing (and we only have time to touch on a few of
them) find a good printer and have him do all your work.
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