WHP034 Addendum 18
Colorimetric and Resolution requirements of cameras
Alan Roberts
ADDENDUM 18 : Panasonic HVX200
Data for this section is taken from short examinations of two production models of the Panasonic HVX200
camcorder. This is a HDTV camcorder, physically very similar to the standard-definition DVX100, with 3
⅓” ccds, the manual gives no clue as to the sensor resolutions. The two models under test ran only at 60 Hz
(actually 59.94) or 50Hz. It records HDTV using the DVCProHD algorithm onto P2 flash cards (1080i,
1080psf, 720p), SDTV using any of the DVCPro50 or DVCPro or DV algorithms onto P2 cards (480i,
480psf, 480psfa* or 576i, 576psf, 576psfa), and SDTV onto miniDV. It can also shoot “off-speed” when
recording 720p onto P2 cards, but only at spot speeds, it is not continuously variable as is the Varicam AJHDC27F.
The camera is relatively light and has an integral lens and viewfinder, with side lcd panel, and seems aimed
at the high-end consumer/professional market rather than full broadcast, which would normally demand
interchangeable lenses. It is the first tapeless camcorder for HDTV. It has a photographic speed of about
640ASA.
It has the usual internal menus for setting the performance, not as complex as in the 720-line Varicam or the
1080-line HDX400, but enough to control most of the important features. It is not suited to multi-camera
operation. It has analogue-only video outputs (components at both HD and SD via a multi-pin connector) and
digits via IEEE1394 Firewire and USB. This alone puts the camera in the consumer/semi-pro market, rather
than broadcast, which would normally expect either HDSDI or BNC connectors for analogue.
The same assessment procedure was used as for other HD cameras, partly attempting to get a good “filmlook”, and the settings reflect that. It is useful to think of the camera, when used in this way, to be
mimicking a film camera and telecine, with “best light” transfer to tape, with about 10 stops of tonal range.
Assuming that a grading operation will be used in post-production, the settings attempt to give the colourist
the same range of options as with film. The recommended settings allow about 1.3 stops of over-exposure
and one of under-exposure relative to normal operation. This is not as good as can be achieved in 2”/3
cameras, and arises from the difference in pixel size (the pixels here are much smaller, so sensitivity is
maintained at the expense of highlight handling and video noise).
1
Colorimetric and Resolution requirements of cameras
Alan Roberts
ADDENDUM 18 : Panasonic HVX200
The assessment of this camcorder was aimed mostly at discovering what it could do, rather than deriving a
preferred setting, results are given in Section 2. The controls are not as flexible as for full “broadcast”
cameras, so it may or may not be possible to derive a specific “film-look” for it. However, there is sufficient
flexibility to achieve much of what is desirable in “film-look” settings. Photographic “speed” is about
640ASA.
Many of the menu items have little or no effect on image quality. Those that have significant effect are
highlighted. The full set of menu items is given for completeness. In boxes with a range of numeric settings,
e.g. -99~99, the values indicate the range, and zero means no alteration to factory setting, not zero effect, and
no scales are given. For each item, the factory setting is given if it is known, and the range offered by the
camera under test. “BBC” settings are in the last column, where appropriate. The following table shows the
menu settings when the camera is in “Camera” mode, these affect picture performance; other menus are
included for completeness. Values that are underlined are the factory default settings. The menus share some
features with the Varicam, in that Scene Files store a great deal of information, permitting widely different
settings to be stored.
BBC-preferred values are given for SD operation, for 1080 interlaced and psf, and for 720 film and sport
(where sport covers all uses that are not intended to look like film). Items that have an important affect on
picture appearance are highlighted. Some items are valid only for tape- or P2-operation, all items are flagged.
It is unfortunate that the colour bars that the camera generates are only 100/0/75/0 (i.e. EBU) rather than the
much more useful SMPTE bars that are ubiquitous in HDTV.
This is not intended as a replacement for reading the manual.
1
Menus and Settings
CAMERA MENU
SCENE FILE
CAMERA SETUP
SW MODE
AUTO SW
RECORDING SETUP
AV IN/OUT SETUP
DISPLAY SETUP
CARD FUNCTIONS
OTHER FUNCTIONS
OPTION MENU
Camera operational controls, needs lab work to get the best from these
Basic camera setup controls
Configuration of switches
Control of camera automatic features
Tape and P2 card controls
Configure audio/video connections
Viewfinder and LCD panel settinmgs
P2 flash card controls
Sundries that don’t fit anywhere else
Control of IEEE1394 (Firewire) connection
MCR/VCR MENU
RECORDING SETUP
PLAYBACK FUNCTIONS
AV IN/OUT SETUP
DISPLAY SETUP
OTHER FUNCTIONS
Timecode, IEEE1394, User bits audio, etc
Audio matters
Analogue connection and IEEE1394 settings
Viewfinder and LCD panel settings
Sundries that don’t fit anywhere else
Control of IEEE1394 (Firewire) connection
OPTION MENU
DUBBING MODE MENU
RECORDING SETUP
DUBBING SETUP
Timecode, IEEE1394, User bits audio, etc
Format, pulldown etc
2
CAMERA MENU
SCENE FILE (1-6)
mode
range
Operation type (P2, tape)
Camera
Video/Film
Frame rate (P2)
Camera
Synchro scan (P2,tape)
Camera
60
50
12, 18, 20, 22, 24, 26,
30, 32, 36, 48, 60
12, 18, 20, 23, 25, 27,
30, 32, 37, 48, 50
Camera
-7~+7
V Detail level (P2,tape)
Camera
-7~+7
Detail coring (P2,tape)
Chroma level (P2,tape)
Chroma phase (P2,tape)
Color temp (P2,tape)
Master Ped (P2,tape)
A. Iris level (P2,tape)
Camera
Camera
Camera
Camera
Camera
Camera
-2~+7
-7~+7
-7~+7
-7~+7
-15~+15
-4~+4
News gamma (P2,tape)
Camera
On/Off
Camera
Knee (P2,tape)
Camera
60
Matrix (P2,tape)
Camera
Skin tone detail (P2,tape)
V Detail freq (P2,tape)
Name edit (P2,tape)
Save/init (P2,tape)
Camera
Camera
Camera
Camera
CAMERA SETUP
mode
Aspect conv (P2,tape)
Camera
Setup (P2)
Setup (tape)
Mid gain (P2,tape)
High gain (P2,tape)
ATW (P2,tape)
Camera
Camera
Camera
Camera
Camera
Handle zoom (P2,tape)
Camera
Iris dial (P2,tape)
Camera
SW MODE
Mid gain (P2,tape)
High gain (P2,tape)
ATW (P2,tape)
mode
Camera
Camera
Camera
Handle zoom (P2,tape)
Camera
Iris dial (P2,tape)
Camera
50
HDnorm, Low,
SDnorm, High,
B.press, Cine-likeD,
Cine-lineV
Auto, Low, Mid, High
Norm, Enriched, Fluo,
Cine-like
Norm1, Norm2, Fluo,
Cine-like
On, Off
Thin, Mid, Thck
Save, Initial
60
60
60
60
60
60
60
50
50
50
50
50
BBC
Shooting speeds for 720p only
n=frame rate, or degrees for FILMCAM,
will not set longer than 1/field or frame
1/n~1/249.8
Detail level (P2,tape)
Gamma (P2,tape)
comments
Also sets SynchroScan indicator to time or
angle
range
Normal, Letter box,
Squeeze
0%, 7.5%
0%, 7.5%
0, 3, 6, 9, 12dB
0, 3, 6, 9, 12dB
Ach, Bch, Prst, Off
L/Off/H, L/M/H,
L/OFF/M
Down open, Up open
range
0, 3, 6, 9, 12dB
0, 3, 6, 9, 12dB
Ach, Bch, Prst, Off
L/Off/H, L/M/H,
L/OFF/M
Down open, Up open
3
0 (1080i)
-2 (1080p)
Horizontal and vertical edge detail +2 (720sport)
-4 (720film)
0 (SD)
-2 (1080i)
-4 (1080p)
Vertical edge detail +3 (720sport)
0 (720film)
-2 (SD)
Noise limiting for detail
+4
Saturation
0
Hue
0
Fine white balance offset
Master black lift
Auto iris gain
Adds some extra knee to cope with
Off
highlights
HDnorm= ITU709, Low=high contrast
HDnorm
(skin press), SDnorm=DVX100,
(HD),
High=black stretch, B.press crushes,
High (SD)
CineV=more contrast than CineD
Reaches ~ 250%, knee at 80%,90%, 100%
90%
Not specifically tested
Reduces skin detail
Thin and Mid may cause twitter
Names the selected scene file
Save changes, or factory reset
comments
Norm/
Norm1
Off
Thin
BBC
Recording format for 480-line
Composite black level for NTSC output
Composite black level for NTSC output
12dB gain is fairly noisy and visibly soft,
probably not acceptable
Assign AutoTrackWhite to gain switch
3dB
6dB
Set zoom speed switch settings,
Reverses iris control (when Manual)
comments
12dB gain is fairly noisy and visibly soft,
probably not acceptable
Assign AutoTrackWhite to gain switch
Set zoom speed switch settings,
Reverses iris control (when Manual)
BBC
3dB
6dB
User 1,2,3 (P2,tape)
Camera
RecCheck, Spotlight,
Backlight, Blackfade,
Whitefade, ATW,
ATWon/off,
Gain18dB,
FocusRing,
IndexMemoP2,
SlotSelP2,
ShotMarkP2
AUTO SW
mode
Camera
Camera
Camera
Camera
range
On, Off
6dB, 12dB, Off
On, Off
On, Off
mode
range
A.Iris (P2,tape)
AGC (P2,tape)
ATW (P2,tape)
AF (P2,tape)
RECORDING
SETUP
60
Rec format (P2)
Camera
50
Rec format (tape)
Camera
480i rec mode (P2)
576i rec mode (P2)
Camera
Rec function (P2)
Camera
One-shot time (P2)
Camera
Interval time (P2)
Camera
Prerec mode (P2)
Camera
Camera/
Vcr/Dub
Camera,
Vcr
Camera
Camera
Camera
Camera
Mcr/Vcr
Camera/
Mcr/Vcr
/ Dub
Camera/
Mcr/Vcr
/ Dub
Camera/
Vcr/
Dub
Camera/
Mcr/Vcr
/ Dub
Rec speed (tape)
Audio rec (tape)
Mic alc (P2/tape)
Mic gain 1 (P2/tape)
Mic gain 2 (P2/tape)
25M rec ch sel (P2)
1394 TC regen (P2/tape)
TC mode (P2/tape)
TCG (P2/tape)
First rec TC (tape)
TC preset (P2/tape)
60
50
60
50
comments
BBC
Auto iris
Set auto gain maximum
AutoTrackWhite
AutoFocus, disables Focus/Push Auto
comments
BBC
1080i/60i, 1080i/30p, 1080i/24p,
Recording format for
1080i/24pa1, 720p/60, 720p/30, 720p/24,
P2 card, this
2
720p/30pn , 720p/24pn, 480i/60i, 480i/30p,
terminology is non480i/24p, 480i,24pa
standard, but the
1080i/50i, 1080i/250, 720p/50p, 720p/250,
meaning is clear.
720p/25pn, 576i/50i, 576i,25p
480o/60i, 480i/30p, 480i/24p, 480i/24pa
Tape recording format
576i/50i, 576i/250
DVCPro50, DVCPro,
Tape compression system
DV
Normal, Interval, One
Non-standard recording functions
shot, Loop
1F, 2F, 4F, 8F, 16F,
Frames or time to record
1s
2F,4F,8F,16F, 1s, 2s,
5s, 10s, 30s, 1m, 5m,
Frames/seconds/minutes
10m
On, Off
Memory cache for prerecording
SP, LP
Tape speed
32k12bit, 48k/16bit
On, Off
-50dB, -60dB
-50dB, -60dB
2ch, 4ch
On, Off
60
Assign user switches.
18dB works only with 60Hz formats, and
not with slow shutter.
P2 options label shots, change slots etc.
Default:1=Whitefade, 2=Backlight,
3=Index/Memo
The usual
Auto level control
External mic level control
External mic level control
DV/DVCPro25 sound channels
On=TC from 1394, Off=other controls
Only relevant in the 59.94Hz variant, 24p
uses NDF
DF, NDF
Free run, Rec run
TC runs free or only when tape runs
Select TC used at start, Regen reads tape
and continues
Regen, Preset
Set initial TC, when recording 24p, set
frame to multiple of 5 for it to make sense
________________________________________________________________________________________________
1
psfa is the slightly improved variant of the 2:3 pulldown process used to derived 60 fields from 24 frames.
Conventionally, 2 fields are made from one frame, then 3 fields from the next; this results in video frames grouped in
sequences of 5, only two of which contains only information from one source frame, the others contain information
from 2 source frames. In this variant, the pulldown sequence is 2:3:3:2, such that only 1 video frame in a group of 5
contains information from 2 source frames. This solves many problem in production and distribution, while somewhat
attenuating the uneven progress of motion caused by the 2:3 process.
2
pn mode records only new frames, for over/undercranking, i.e. there is no frame repetition.
4
1394 UB regen (P2/tape)
UB mode (P2/tape)
UB preset (P2/tape)
1394 In preset (P2/tape)
PLAYBACK
FUNCTIONS
32k audio (tape)
Audio out (P2)
Audio out (tape)
PLAYBACK
FUNCTIONS
Mcr/Vcr
Camera/
Mcr/Vcr
/ Dub
Camera/
Mcr/Vcr
/ Dub
Mcr/Vcr
On, Off
User, Time, Date,
TCG, FrmRate
On, Off
range
comments
Vcr
ST1, ST2, Mix
Ch1Ch2, Ch1, Ch2,
Ch3Ch4, Ch3, Ch4
Route stereo 1/2 or 3/4 to output when 32k
Channels 3 and 4 available only on P2
recording
range
comments
Mcr.Vcr
mode
60
60
Pulldown sel (tape)
Setup (tape)
Dub
Dub
60
60
mode
50
Dub
50
AV IN/OUT
SETUP
Cmpnt out sel (P2)
HP mode (P2,tape)
A.dub input (tape)
1394 out (tape)
DISPLAY SETUP
Sync TCG to 1394 when TCSet pressed
mode
Dub
Format sel (P2)
FrameRate uses a code, refer to manual
Set info, select User in UB mode
Format sel (P2)
DUBBING SETUP
Source of UserBits
mode
Camera/
Mcr
Camera
Vcr
Vcr
1080i/60i, 1080i/30p,
1080i/24p,
1080i/24pa, 720p/60p,
720p/30p, 720p/24p,
720p30pn, 720p/24pn
24p, 24pa
0%, 7.5%
range
1080i/50i, 1080i/25p,
720p/50p, 720p/25p,
720p/25pn
range
BBC
BBC
Clip format for dub playback
23 or 2332 pulldown to 60
Composite setup for NTSC
comments
BBC
Clip format for dub playback
comments
BBC
720p, 1080i, 480i
720p converts only to 1080i
Live, Recording
Mic, A.In
On, Off
Headphone feed, use Live for off-speed
Take sound from mics or audio I/O
On feeds analogue inputs to 1394, adc
Zebra detect 1 (P2,tape)
mode
Camera
Zebra detect 2 (P2,tape)
Camera
Marker (P2,tape)
Safety zone (P2,tape)
Camera
Camera
range
50%~105% by 5%
50%~105% by 5%,
Off
On, Off
Off, 90%, 4:3
Video out OSD (P2,tape)
Camera
On, Off
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
Off, Time, Date,
Time&Date
What to show on screen
On, Off
Audio levels on screen
Date/Time (P2,tape)
Level meter (P2,tape)
Zoom, focus (P2,tape)
Card/Tape, Batt (P2,tape)
Other display (P2,tape)
Camera data (P2,tape)
LCD backlight (P2,tape)
LCD set (P2,tape)
EVF set (P2,tape)
Self shoot (P2,tape)
Camera
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
Mcr/Vcr
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
Camera
comments
Default 80%, left-leaning zebra
Default 100%, right-leaning zebra
Press Zebra button to display markers
Screen info to video output, beware, it goes
to 1394 as well
Off, Number,
mm/feet, mm/mm
Show real distances (maybe☺)
On, Off
Remaining capacity
Off, Partial, All
Display info depth
On, Off
Show camera settings on playback
High, Normal
Brightness
Panel, set brightness, contrast, colour
V/F, set brightness, contrast, colour
Normal, Mirror
5
For when panel is forward-facing
BBC
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
On, Auto
Auto switches off V/F when panel is open
Auto, 4:3
Widescreen always appears letterboxed
mode
range
comments
Scene file (P2)
Camera
Read, Write
User file (P2)
Camera
Read, Write
Save up to 4 scene files to P2 card
Save up to 4 file settings (not Scene) to SD
card
SD card format
Camera
EVF mode (P2,tape)
Display aspect (P2,tape)
EVF color (P2,tape)
CARD
FUNCTIONS
OTHER
FUNCTIONS
On, Off
For black/white V/F
mode
range
Remote (P2,tape)
Camera/
Mcr,Vcr
Vcr1, Vcr2, Off
1394 control (P2,tape)
Camera
Off, Ext, Both Chain
1394 cmd sel (P2,tape)
End search (tape)
PC mode (P2)
Rec lamp (P2,tape)
Access led (P2)
Beep sound (P2,tape)
Clock set (P2,tape)
Time zone (P2,tape)
Power Save (P2,tape)
Language (P2,tape)
User file (P2,tape)
Hour meter
OPTION MENU
1394 status (P2,tape)
1394 config (P2)
Camera/
Vcr
Camera/
Mcr
Camera/
Mcr
Camera
Camera/
Mcr
Camera
Camera/
Mcr/Vcr
Camera/
Mcr/Vcr
Camera
Camera/
Mcr/Vcr
Camera/
Mcr,Vcr
Camera/
Vcr
comments
RecP, Stop
BBC
BBC
Remote control access
Backup via 1394, Ext controls remote deck
with Start/Stop, Chain uses remote deck as
extra recorder
Set remote deck to stop or pause
Blank, Rec End
USB device, 1394
device, 1394 host
Off, Front, Rear, Both
On, Off
Search for unrecorded slot or last recording
1394 host controls external deck for backup
Card access indicator
Warns of card/tape full, no tape,
condensation, problem
Set clock and calendar. Really, honest,
that’s what it does
On, Off
-12~+13
Time zone offset from GMT, for foreigners
On, Off
Disables 5-minute inactive shut-down
English, Japanese
Menu language, use with care
Load, Save, Initial
Power down/up to activate change
Shows head hours (5 digits per hour)
Press Disp/Mode Chk button and Menu, then Menu to cancel
mode
range
comments
P2: Format, rate, 50/60, channels, speed,
Camera/
status, video, audio
Mcr/Vcr
Tape: Format, rate, 50/60, channels, speed,
mode, Rx, Tx
Camera/
Dflt, 1~255
1394 extended menus
Mcr
6
BBC
2
Measurement results
The HVX200 has no built-in test signal generator. This alone sets it apart from most professional and
broadcast cameras. Thus all measurements had to be made the hard way, using optical test cards and an
awful lot of data processing. Only the 50Hz version was measured in detail, serial number C6TC0015-R.
2.1 Transfer characteristic (gamma-correction)
Measurements were made to determine the equations of two of the
gamma-correction curves, which also revealed the nominal exposure
range of the camera. A Macbeth (Fig.1) chart was evenly illuminated,
and recordings made at the full range of exposures. The bottom row of
colour patches on the chart forms a grey scale, and the optical density
of each patch is given in the specifications of the card, thus it was
possible to obtain a large number of measurement points to form a
point-wise plot of the gamma-correction curves. Since the iris control
is continuous, it was not possible to set exposure precisely for each
exposure, nevertheless, judicious adjustments in the data processing
has provided a reasonable data set from which to estimate the gammacorrection curves.
Fig. 2 shows data points for the
Hdnorm curve (supposed to be
the ITU.709 curve) with Knee set
to Mid (which is supposed to
break at 90% voltage). It is
relatively easy to fit a curve to
these points, but it is not easy to
be accurate since there is clearly
some inconsistency in the data,
caused by video noise, slightly
uneven
illumination,
lens
vignetting when fully open,
imprecise setting of the iris, and
so on.
Figure 1, Macbeth chart
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
The ITU.709 curve, the standard
for all HDTV cameras is:
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
Figure 2, HDnorm gamma, Knee=Mid
V = 4.5 L for L<0.018, else V = 1.0099 L ^ 0.45 − 0.099
The found equations for the Hdnorm curve are:
V = 4.5 L for L<0.03, else V = 1.05 L ^ 0.5 − 0.05
This is a reasonable match to ITU709, but is not perfect. The Knee causes the curve to break at signal levels
of 80% (Low), 90% (Mid), 100% (High) and then extend to and exposure limit of 2.5 (250%) before clipping
occurs at about 107%.
The contrast range for these settings is derived from the equations. The maximum exposure the camera can
handle is 250%, while the minimum exposure that is visible in the output can be defined as that which causes
the signal voltage to be 2% of the coding range (the video level of the super-black bar in SMPTE colour bars,
used for setting display black level). If the noise is low, then a lower point can be taken, 1% would be the
normal minimum considered relevant. For the Hdnorm curve, these ratios are approximately 550:1 (9.1
stops) and 1100:1 (10.1 stops), not bad for a camera in this category. Measurements of the High (Black
Stretched) gamma-correction curve were surprising, the found equations are:
V = 5 L for L<0.02, else V = 1.25 L ^ 0.33 − 0.25
However, the numbers in this equation are a little extreme, so in a second search a rather better match to the
data was found by fitting the BBC 0.4 law to it:
7
V = 5 L for L<0.02262, else V = ((L − 0.037703) (1 − 0.037703))^ 0.4
Both these curves fit the data well, but the BBC
curve (which was designed for SDTV use) seems
more natural, and is presumably intended to be so.
This gamma-correction curve generally produces
more accurate colour rendering. Fig. 3 shows the
colour accuracy of the camera using the Hdnorm
curve; each colour is shown as a blob where it
should be and a cross where the camera produces it.
There are significant saturation and hue errors, most
significantly in skin tones.
The user should generally choose one of these two
curves for working in HDTV, Hdnorm produces
more vivid colouring while High is more accurate.
For normal use, Knee can be set to Auto, but when
the production will be going to a colour grading
operation, Knee should be set either to Mid or Low,
depending on the type of programme (Mid for
programmes where skin tone is prevalent, Low for
natural-history).
The other variants of the gamma curve were not
investigated, the descriptions given in the manual
seem to be sufficiently accurate and explicit for
the user to make an intelligent choice.
Figure 3, chromaticity of HDnorm curve
2.2 Resolution and Detail
The HVX200 is interesting in that the sensors are not native-sized for HDTV. The 3 ccds are each
960 by 540 pixels; it would be more usual to find sensors, in a 1080-line camera, having 1080 lines
rather than only 540. Panasonic chose to use these lower-resolution sensors in order to increase
sensitivity (since the pixels are bigger, the same 5µm square dimension as is found in ⅔” format
HDTV cameras. The camera delivers HDTV resolutions by physically offsetting the G sensor from
R and B by a half-pixel both horizontally and vertically. It is normal to offset just horizontally,
when the delivered horizontal resolution is apparently about 50% higher than would be dictated by
the pixel count alone. This quincunx offset increases both horizontal and vertical resolution, just
how well can only be judged by measurement. This particularly relevant since the camera delivers
signals at 1080, 720 and SDTV (both 576 and 480 lines in the two variants).
A zone plate test chart was used, calibrated for 1920x1080 HDTV. It contains 6 identical circular
patterns, each being a phase space of the spatial-frequencies which such a camera should resolve.
Analysis was made of one zone to investigate the frequency responses and the presence of aliases.
2.2.1 Detail enhancement
However, a broad pulse (also on the zone plate test chart)
was used for establishing reasonable detail settings, since
the function of the detail enhancement is to sharpen edges
rather than establish flat frequency responses. Fig.4
shows the effect of setting Detail Level to 0 and –2, there
was no setting at which the overshoots were absent, and
insufficient other controls to alter the way the
enhancement works. Judging by eye, setting level –2
seemed reasonable.
8
Figure 4, 1080-line pulse response
2.2.2 Resolution (1080-line)
Fig.5 shows a quarter of one circular zone plate, with zerofrequency at bottom left. The right-hand extreme is 1920
lines/picture width, the top extreme is 1080 lines/picture
height. The alias patterns are clear, and indicate that the
camera does not deliver full resolution at 1080, either
horizontally or vertically. However, it is reasonably well
behaved, in that there do not appear to be significant aliases
centred on other frequencies, as would be expected if the
interpolation process from the 960x540 of the ccds were
compromised in any way. The precision-offset of the sensors
in cameras is normally only horizontal, which delivers
approximately 50% more horizontal resolution than the
pixel-count, but with sensors in quincunx arrangement both
horizontal and vertical resolutions are increased, but how
well and by how much is debatable.
Figure 5, quarter zone plate,
1080psf/25, detail=-2, v.detail=-4
The strength of the existing aliases mean that it is difficult to
measure the frequency responses accurately, since the higher
frequencies are mixed with aliases. Nevertheless, it was
possible to extract sufficient data using a software analysis
program, to derive both horizontal and vertical frequency
responses, and these reveal some interesting information.
Figs.6 and 7 show the horizontal and vertical responses for
1080i/25p (usually known as 1080psf/25, film style). It is
difficult to decide how to present the amplitudes at greater
than 960 horizontal and 540 vertical. It is clear that aliases
(unwanted) are present, but so is content at baseband
(wanted) frequencies. Since the recording format has a
horizontal limit of 1440, not 1920, horizontal frequency
content above 1440 must be only alias, there can be no
baseband content.
In both figures, the green curve shows the response when
both Detail Level and Vertical Detail are set to 0, the default
value. Clearly, the designers have realised that it is more
dangerous to have excess vertical detail over horizontal, but
both curves seem excessively boosted at low/mid frequencies;
it is in these low/mid frequencies that detail must be well
controlled in order to generate a decent “film-look”, neither
of these curves will do. To show how difficult it is to
interpret the available measurements, Fig.8 shows the
sequence of sample levels in a horizontal scan.
The settings given in Section 1 are not ideal; they are
subjectively a reasonable compromise, but overall
performance of the camera is not a good match to other
HDTV cameras in this respect.
Figure 6 and 7, horizontal and
vertical responses, 1080psf
Figure 8, horizontal waveform
2.2.3 Resolution (576-line)
Again, interpretation of data is difficult, but the subjective appearance of resolution is reasonable.
Fig.9 shows the horizontal frequency response. The bandwidth is well filled to the 720-pixel limit
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(perhaps too well filled), but there are significant aliases between 720 and 1440, and the frequencies
between 1440 and 1920 show strongly because they are twice-folded.
Evidently the Detail controls apply only detail-boosting
(some HDTV cameras have detail controls that allow
detail reduction as well as boosting). For SDTV use
boosting is largely unnecessary, so a very low setting is
reasonable, in Fig.9 the Detail setting level is 0, and is
clearly too much. Judging by eye, a setting level of –2
is the maximum that should be used, and –4 looks better
although the picture then starts to look soft because the
boosting is done at too low a frequency even in the Thin
setting. The settings in the table produce pictures that
look sharp at the expense of some visible boundary
enhancement.
The same does not hold for the vertical response,
Fig.10, the response falls nicely to zero between 288
and 576, resulting in a moderate amount of interline
twitter. The complete lack of vertical aliases at higher
frequencies is good evidence that the camera can be
used to shoot SDTV pictures, provided Detail is set
sufficiently low.
Figure 9, horizontal response
Figure 10, vertical response
2.2.4 Resolution (720-line)
At the time of testing, it was not possible to analyse single frames of P2 recording, however the
visual appearance was a good intermediate between 1080 and 576. The Detail settings in the table
are visually appropriate for film- and sport-style shooting, where the film version uses minimal
boosting although there is no setting that gets satisfactorily close to a real film-look. The sport
version is appropriate for news, sports, any genre other than film-look.
2.3 Noise
No calibrated noise meter was available during the measurement procedure, and the camera
specification does not mention noise. Again, software analysis of frames gives some indication of
performance. Measuring the signal-to-noise ratio is just one colour patch of the Macbeth chart (the
white patch when slightly under-exposed, 0db Gain) gives a figure of 44dB. Although it is highly
dangerous to use such a small number of samples for analysis, the error is known to be less than
2dB, thus noise is between 42dB and 46dB. This agrees with subjective evaluation, and explains
the high value set for Detail Coring. At +12dB, the noise is plainly visible; even with Detail
Coring set to +4, the noise level was sufficiently high to cause detail enhancement to switch off,
resulting in visibly softened pictures. This explains the Gain settings of +3dB and +6dB.
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