PlanIt! User Guide

With the auto-exposure (AE) in modern cameras, many photographers started to forget the concepts
such as exposure value, exposure triangle, and exposure compensation as they depend on the camera to
do it for you. However, knowing the exposure is still key to successful photo shots. The Exposure page
will let you experiment the exposure settings beforehand, so that you don’t need to fumble with the
camera settings while the perfect timing lapsed before you.
Exposure Mode
Exposure Value
at ISO 100
With ND
Filter or not
Exposure value (“EV”) represents equivalent combinations
of lens aperture and shutter speed that result in the same
exposure for given lighting conditions. For a given ISO
speed of the film or sensor, EV corresponds to a specific
light level; by convention, values are given for ISO 100,
and indicated as “EV at ISO 100” or sometimes “EV100”.
See the Wikipedia article Exposure value for more
information. In the PlanIt, “EV” always means “EV100”.
Shutter Speed
What does this mean? It means in a scene with exposure
value of 15, if you are using shutter speed 1/250,
aperture f/8, ISO 100 to take a picture, you will get a
picture that is 1 stop over exposed.
You may ask, how do I know the exposure value for the
scene is 15? Answer: It is mostly by experience but this
app can help.
Exposure Value
Let’s review some typical exposure settings.
Sunny 16 rule: On a sunny day and with ISO 100
film / setting in the camera, one sets the aperture to
f/16 and the shutter speed to reciprocal of the ISO.
For example if the aperture is f/16, the ISO is 100,
then the shutter speed would be 1/100 of a second.
See below. It means the exposure value for the
sunny day is 14.6.
Looney 11, 8, 5.6 rule: On a clear day and when the full
moon is high in the sky, with ISO 100 film / setting in the
camera, one sets the aperture to f/11 and the shutter
speed to reciprocal of the ISO. For example for the full
moon, if the aperture is f/11, the ISO is 100, then the
shutter speed would be 1/100 of a second. If the Moon is
a gibbous or half moon, change the aperture to f/8. If
crescent moon, change the aperture to f/5.6.
Night Skyline rule: For city skyline at night, one
sets the shutter speed to 30 seconds, aperture to f/8
and ISO to 100.
Milky Way rule: For milky way photo at dark night,
one sets the shutter speed to 30 seconds, aperture
to f/2.8 and ISO to 3200.
Exposure Value for Some Typical Cases
From the previous page, you should have some
ideas of the exposure values for some typical cases.
Exposure Value
at ISO 100
If you tap on the Exposure Value, you will see a list of
exposure values and the corresponding scenarios. I
highlighted four of them. Those are exposure values
used on the previous page.
You may want to capture two subjects with different
exposure values, i.e. a full moon at EV 14 and a night
skyline at EV 1. The difference is 13 stops. Modern
cameras can capture up to 10 to 11 stops, which means
there is no way you can capture both in one photo
without one over exposed or the other one underexposed. Knowing that beforehand, you will be well
prepared to take two photos using different exposure
ND Filter Calculator
Tap on the Manual or the first button on the
Exposure page to choose a different mode.
Exposure Mode
Select the ND Calculator, you will see the calculator
Tap the shutter speed on the first row to choose the
shutter speed before adding the ND filter. Tap on
the filter button to choose the ND filter, the shutter
speed on the second row will be the shutter speed
after using the ND filter you choose.
Scene Exposure Mode
So far, you may notice the exposure page has nothing to with the current time or the map below it. That’s right. But if you
choose the Scene Mode, the map and the current time will be used. Simply speaking, the Scene Mode provides the
suggestion for the exposure settings based on the current time and the location considering the Sun and the Moon
elevation. Note the time of the day and the EV value. The EV value was set by the app when the time changes.
A clear day at
EV = 15
A clear day at
EV = 5.5
A clear day at
blue hour starts
EV = 1.6
A clear day at
dark night starts
EV = -6
Scene Exposure Mode – Other Subjects
You can also tap on the EV value to select a different weather condition or subjects. For example, an overcast day would
have different exposure than a clear day. If the correct exposure for a moon is certainly different from the exposure for
skyline at the night, event they are at the same time.
Skyline at Night
EV = 1
Moon as subject
EV = 14
Stars as subject, but this
exposure setting will cause
EV = -5.0
Stars as subject,
no more streaks
EV = -5.0
Light Meters
We embedded an incident light meter and reflected light meter
in the Android version of the app and only the reflected light
meter for the iOS version.
These light meters are not meant to
replace a professional light meter
because it can not detect low light very
well. Anything below EV 1 are not
Read Exposure Settings from a Picture
The last mode in the Exposure page is the Picture mode. It loads
a picture from your phone and read the exposure settings (part
of the EXIF) from it if they are available.
Tap here to load a picture
These three values are read from the
picture. The EV was calculated from
them automatically.
This message means the EXIF is
available. If not available, it will show the
message here.
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