Homebrew standard video test charts?

[msg]

I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

2. Luma staircases, 12 step, consisting of two horizontal bands of
opposite gradient separated by a central square (of some unknown
value) as provided by Panasonic gray scale chart VFKS003A (reflective)
and VFKS002A (transmissive). (Anyone have access to this chart or
something similar to describe what is in the center?)

I have a number of YUV and BMP files for standard test patterns, and
to my surprise, the full color bar files differ in choices of hue,
saturation and value (in RGB space) for what are labeled 75% bars
for example, so I would appreciate some thoughts on how the
colors should be defined.

I know little about printing and have no photometer, only the
controls provided by Windows printer drivers. For color printing
I have a wax transfer and/or dye sub ALPS MD5000 and for B&W there
are a number of laser printers up to 1200DPI native. What size
paper should be used for charts to be shot at a distance of five
feet? How does one choose a paper stock and deal with reflectance
values of paper and ink?

Could one conceivably make color test charts using paint swatches
from the paint store? Would a commercial standard chart, brought
into the store to be scanned by the in-store spectrophotometer,
be necessary to do the matching? If so, perhaps I can check out
such a chart from the local public access TV folks.

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

Michael

 

[Dave Plowman (News)]

In article <-rmdnXAWTLHb1PrXnZ2dnUVZ_tSdnZ2d@posted.cpinternet>,
msg <msg@_cybertheque.org_> wrote:

I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

I'm a bit out of it these days, but never saw such a chart used on studio
cameras. Only 'chart' they used colour wise was a painted head for colour
matching reasons. Surrounded by a grey card and grey scale. I'd say it
extremely difficult to print anything accurate enough.

--
*Sherlock Holmes never said "Elementary, my dear Watson" *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[GregS]

In article <-rmdnXAWTLHb1PrXnZ2dnUVZ_tSdnZ2d@posted.cpinternet>, msg <msg@_cybertheque.org_> wrote:

I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

2. Luma staircases, 12 step, consisting of two horizontal bands of
opposite gradient separated by a central square (of some unknown
value) as provided by Panasonic gray scale chart VFKS003A (reflective)
and VFKS002A (transmissive). (Anyone have access to this chart or
something similar to describe what is in the center?)

I have a number of YUV and BMP files for standard test patterns, and
to my surprise, the full color bar files differ in choices of hue,
saturation and value (in RGB space) for what are labeled 75% bars
for example, so I would appreciate some thoughts on how the
colors should be defined.

I know little about printing and have no photometer, only the
controls provided by Windows printer drivers. For color printing
I have a wax transfer and/or dye sub ALPS MD5000 and for B&W there
are a number of laser printers up to 1200DPI native. What size
paper should be used for charts to be shot at a distance of five
feet? How does one choose a paper stock and deal with reflectance
values of paper and ink?

Could one conceivably make color test charts using paint swatches
from the paint store? Would a commercial standard chart, brought
into the store to be scanned by the in-store spectrophotometer,
be necessary to do the matching? If so, perhaps I can check out
such a chart from the local public access TV folks.

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

Michael

I might first suggest looking at the test patterns for digital camers
off the camera test sites. I have used those befors for
different things.

For example. I look at my cameras image here. Printing
is necessary.

http://www.imaging-resource.com/PRODS/S2000HD/S2000HDhMULTI1600.HTM

Might also try sci.engr.television.broadcast

 

[GregS]

In article <h47mqm$5a1$1@usenet01.srv.cis.pitt.edu>, zekfrivo@zekfrivolous.com (GregS) wrote:

In article <-rmdnXAWTLHb1PrXnZ2dnUVZ_tSdnZ2d@posted.cpinternet>, msg
msg@_cybertheque.org_> wrote:
I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

2. Luma staircases, 12 step, consisting of two horizontal bands of
opposite gradient separated by a central square (of some unknown
value) as provided by Panasonic gray scale chart VFKS003A (reflective)
and VFKS002A (transmissive). (Anyone have access to this chart or
something similar to describe what is in the center?)

I have a number of YUV and BMP files for standard test patterns, and
to my surprise, the full color bar files differ in choices of hue,
saturation and value (in RGB space) for what are labeled 75% bars
for example, so I would appreciate some thoughts on how the
colors should be defined.

I know little about printing and have no photometer, only the
controls provided by Windows printer drivers. For color printing
I have a wax transfer and/or dye sub ALPS MD5000 and for B&W there
are a number of laser printers up to 1200DPI native. What size
paper should be used for charts to be shot at a distance of five
feet? How does one choose a paper stock and deal with reflectance
values of paper and ink?

Could one conceivably make color test charts using paint swatches
from the paint store? Would a commercial standard chart, brought
into the store to be scanned by the in-store spectrophotometer,
be necessary to do the matching? If so, perhaps I can check out
such a chart from the local public access TV folks.

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

Michael

I might first suggest looking at the test patterns for digital camers
off the camera test sites. I have used those befors for
different things.

For example. I look at my cameras image here. Printing
is necessary.

http://www.imaging-resource.com/PRODS/S2000HD/S2000HDhMULTI1600.HTM

Might also try sci.engr.television.broadcast

Well I could have selected a better camera.........

http://www.imaging-resource.com/PRODS/D300/D300hMULTI4288F.HTM

 

[Wild_Bill]

I've often wondered how one can absolutely determine if a video camera is
properly color calibrated.

You don't explain what you want to acomplish.. certifying that a camera is
operating within the manufacturer's original specifications, or finding the
best balance of colors that a used camera is capable of.

I've seen the technical literature procedures and color/light boxes, but any
piece of test equipment or color analyzer will have some variations. Even
the charts from different sources will have inconsistent variations. If the
charts are colored plastic sheets, exposing them to fluorescent lighting
might fade them a bit. The output of the lamps in the light boxes will most
likely vary by brand, or even differences in voltage.

As far as attempting to fabricate a light box for colors, I would assume
that a well-stocked art supply company would have plastic sheets in a wide
range of colors, but other than an art supply, the only other source I can
think of might be a specialized stage lighting supplies business. Either of
these might have products that have some standardized specifications
associated with their products.. #112 red related to a specific color, as a
guess (kinda similar to the way camera filter numbers are standardized).

A piece of equipment that's nearly always present with commercial video
production is the waveform monitor, and often paired with a vector monitor.

Aside from the source colors being nearly perfect, monitoring displays will
have differences, certainly between CRT and LCD or other display technology.

So then an analyzer is needed to determine if the monitor is delivering an
accurate representation of the source signals.

The source product my be nearly perfect compared to some EIA or other
standard, but then in commercial TV broadcasting, the video progrmming has
to pass thru other levels of signal processing and transmission equipment,
it's all quite extrordinary.

Finally, the consumer adjusts their monitor levels to their own preferences
(or they don't have any) and the video may look like a 4-year old colored
the displayed image with only 4 or 5 crayons.

The studio and field use ENG broadcast cameras are originally set up by the
manufacturer, and may go thru numerous alignments in the useful service
life, which I suspect are sometimes TLAR that looks about right, or close
enuff.

Between the cameras and the transmitters there are likely to be a
considerable number of pieces of equipment dedicated as auto-level
compensators for various signal parameters.
At one time, the controls for these adjustments were probably the
responsibility of a broadcast station engineer, for the engineer to monitor
and adjust as required.

It's very interesting to play with a color corrector to adjust the levels
from different sources to get them to look nearly identical.
For a small-scale production setup, I would think that a color corrector
would be an absolute necessity.

In the movie industry, many varied shots are made with vastly different
equipment, sometimes by choice and other times by necessity.
I watched a director explain that anything from 8mm film, various types of
video, and high-end wide film are sometimes combined to create a movie.
In another example Spielberg(?) was explaining that the color levels were
intentionally reduced in Saving Private Ryan, and when the movie made it's
way to cable, the program providers were swamped with phone call complaints
that the colors were too weak, so the providers adjusted the levels. OK,
TLAR.

I suspect that much of the final product is corrected by specialized
computers in most movie and TV productions.
Viewers might expect a different level of color rendering for a product such
as a nature film where everything should look natural.

--
Cheers,
WB
..............


"msg" <msg@_cybertheque.org_> wrote in message
news:-rmdnXAWTLHb1PrXnZ2dnUVZ_tSdnZ2d@posted.cpinternet...

I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

2. Luma staircases, 12 step, consisting of two horizontal bands of
opposite gradient separated by a central square (of some unknown
value) as provided by Panasonic gray scale chart VFKS003A (reflective)
and VFKS002A (transmissive). (Anyone have access to this chart or
something similar to describe what is in the center?)

I have a number of YUV and BMP files for standard test patterns, and
to my surprise, the full color bar files differ in choices of hue,
saturation and value (in RGB space) for what are labeled 75% bars
for example, so I would appreciate some thoughts on how the
colors should be defined.

I know little about printing and have no photometer, only the
controls provided by Windows printer drivers. For color printing
I have a wax transfer and/or dye sub ALPS MD5000 and for B&W there
are a number of laser printers up to 1200DPI native. What size
paper should be used for charts to be shot at a distance of five
feet? How does one choose a paper stock and deal with reflectance
values of paper and ink?

Could one conceivably make color test charts using paint swatches
from the paint store? Would a commercial standard chart, brought
into the store to be scanned by the in-store spectrophotometer,
be necessary to do the matching? If so, perhaps I can check out
such a chart from the local public access TV folks.

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

Michael

 

[Martin Heffels]

On Wed, 22 Jul 2009 12:17:14 -0500, msg <msg@_cybertheque.org_> wrote:

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

Maybe the C1 chart of Coloraid could be the thing for you?

http://www.targets.coloraid.de/

It's for photography, but I guess you could create a colourprofile for
your videocamera with it as well. I got a chart of them to calibrate
my scanner once in a while, after reading positive comments about the
accuracy of the charts.

cheers

-martin-

 

[msg]

msg wrote:

I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

<snip>

2. Luma staircases, 12 step, consisting of two horizontal bands of
opposite gradient separated by a central square (of some unknown
value) as provided by Panasonic gray scale chart VFKS003A (reflective)
and VFKS002A (transmissive). (Anyone have access to this chart or
something similar to describe what is in the center?)

<snip>

Could one conceivably make color test charts using paint swatches
from the paint store? Would a commercial standard chart, brought
into the store to be scanned by the in-store spectrophotometer,
be necessary to do the matching? If so, perhaps I can check out
such a chart from the local public access TV folks.

I found the gray scale reflectance chart at our public access tv
operation and checked it out for a few weeks to permit attempts to
duplicate it. Indeed it uses 'chips' (swatches) of continuous tone
pigment pasted onto a uniform background. The center square is still
a bit of a mystery; on this chart, it is a piece of black velvet
fabric. For the archives I will quote the instructions as pasted
on the rear of the chart (typed with 80 char max line length):

---------------------------------------------------------------------
INSTRUCTIONS FOR GRAY SCALE REFLECTANCE CHART LOGARITHMIC REFLECTANCE
CHART

General Description. The chart consists of a pair of gray scales running
in opposite directions on a uniform 12% reflectance gray background.
The scales begin with Black (3% reflectance), increasing logarithmically
to White (60% reflectance). Table 1 shows the Nominal (ideal)
Reflectance of the Gray Scales on the accompanying chart.

Table 1: Nominal Data for Logarithmic Reflectance Chart
Gray Scale Chip No. 1 2 3 4 5 6 7 8 9
Nominal Reflectance 60.0 41.3 28.4 19.5 13.4 9.2 6.3 4.4 3.0
of Chip (% relative
to MgO)

Use. Electrical measurement and adjustment of the camera chain equipment
should be made first. Reflection measurements and adjustments should be
made only after proper scanning, electrical and optical focus, coarse
shading, and registration have been accomplished. The chart should be
televised by the camera and reproduced on suitable picture and waveform
monitors. It should be uniformly lighted in accordance with usual studio
and mobile practices.

Checking the Transfer Characteristics. For a monochrome camera the camera
output without gamma correction, when viewed on a waveform monitor at line
rate, should appear as crossed stairsteps. This presentation is a
logarithmic measure of the transfer characteristic of the camera and
associated amplifiers. The crossed stairsteps should have the same total
height and no step should exhibit appreciable tilt. Any abnormal tilt or
difference in total height indicates incorrect shading adjustment. If
gamma correction is used to give an overall system gamma of about unity,
the steps will appear almost linear on the waveform monitor. With gamma
correction, the output, when viewed on a picture monitor should appear as
a faithful reproduction of the brightness steps of the chart on a flat field.
Any severe departure from faithful reproduction of the original gray scale
indicates that the system transfer characteristic is non-linear. Any abnormal
departure from a gray field indicates incorrect shading.

For a Color Camera. A monochrome reflectance chart of the correct color
temperature should appear on the color picture monitor. The picture should
appear as a faithful reproduction of the brightness steps of the chart on a
flat gray field. Any variation in chromaticity along the gray scale indicates
that the transfer characteristic of the three color channels do not match.
Any variation in color of the uniform gray background of the chart indicates
that the shading characteristics of the three channels are not matched.

When viewed on a waveform monitor at line rate, the composite color video
signal should appear as crossed stairsteps. The crossed stairsteps should
have the same total height, and no steps should exhibit appreciable tilt.
No trace of the subcarrier should appear on any of the steps or on the gray-
surround line.

Rating and Matching Pick-Up Tubes. The techniques of determining the relative
sensitivities, the matching of multi-tube groups, and the general adjustment
of cameras depends upon the type of pick-up tube. The user should refer to
the manufacturer's manual for these details.

Manufactured and Distributed by Hale Color Consultants, Inc. 1505 Phoenix
Road Phoenix, MD 21130 (301) 472-4850

Television Test Charts should be handled carefully and protected from undue
exposure to strong light, which can fade the colors and reduce their
usefulness. Charts have an average wear-out life of two years, after first
use. This chart should be replaced not later than --Feb 1988--
----------------------------------------------------------------------------

Now, it's off to the paint store...

Michael

 

[msg]

GregS wrote:

<snip>

Michael

I might first suggest looking at the test patterns for digital cameras
off the camera test sites. I have used those before for
different things.

For example. I look at my cameras image here. Printing
is necessary.

http://www.imaging-resource.com/PRODS/S2000HD/S2000HDhMULTI1600.HTM

Might also try sci.engr.television.broadcast

Thanks for both of those; I have been collecting test pattern files for
awhile and appreciate your link too.

Michael

 

[msg]

Martin Heffels wrote:

On Wed, 22 Jul 2009 12:17:14 -0500, msg <msg@_cybertheque.org_> wrote:

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

Maybe the C1 chart of Coloraid could be the thing for you?

http://www.targets.coloraid.de/

It's for photography, but I guess you could create a colourprofile for
your videocamera with it as well. I got a chart of them to calibrate
my scanner once in a while, after reading positive comments about the
accuracy of the charts.

Thanks for your suggestion; I do have an IT 8.7 (Agfa) target and will
take that with me to the paint store to use for comparisons. Perhaps
scanning it on a flatbed scanner at the store, noting the color data
as the scanner saw it, and then scanning paint store 'chips' and noting
their values would make for a quick and dirty color comparitor.

Michael

 

[msg]

Wild_Bill wrote:

I've often wondered how one can absolutely determine if a video camera
is properly color calibrated.

You don't explain what you want to acomplish.. certifying that a camera
is operating within the manufacturer's original specifications, or
finding the best balance of colors that a used camera is capable of.

Actually it is for setup and calibration of the homebrew studio camera
I described in a previous thread...

I've seen the technical literature procedures and color/light boxes, but
any piece of test equipment or color analyzer will have some variations.
Even the charts from different sources will have inconsistent
variations. If the charts are colored plastic sheets, exposing them to
fluorescent lighting might fade them a bit. The output of the lamps in
the light boxes will most likely vary by brand, or even differences in
voltage.

As I have learned by the caveats printed on the back of the reflectance
chart which I borrowed today.

As far as attempting to fabricate a light box for colors, I would assume
that a well-stocked art supply company would have plastic sheets in a
wide range of colors, but other than an art supply, the only other
source I can think of might be a specialized stage lighting supplies
business. Either of these might have products that have some
standardized specifications associated with their products.. #112 red
related to a specific color, as a guess (kinda similar to the way camera
filter numbers are standardized).

I will need to find a certain blue filter for one set of adjustments and
other than a camera shop, the art supply store sounds promising.

A piece of equipment that's nearly always present with commercial video
production is the waveform monitor, and often paired with a vector monitor.

Aside from the source colors being nearly perfect, monitoring displays
will have differences, certainly between CRT and LCD or other display
technology.

So then an analyzer is needed to determine if the monitor is delivering
an accurate representation of the source signals.

Would be nice to find one of those suction-cup photometers someday for
calibrating monitors.

The source product my be nearly perfect compared to some EIA or other
standard, but then in commercial TV broadcasting, the video progrmming
has to pass thru other levels of signal processing and transmission
equipment, it's all quite extrordinary.

Finally, the consumer adjusts their monitor levels to their own
preferences (or they don't have any) and the video may look like a
4-year old colored the displayed image with only 4 or 5 crayons.

The studio and field use ENG broadcast cameras are originally set up by
the manufacturer, and may go thru numerous alignments in the useful
service life, which I suspect are sometimes TLAR that looks about right,
or close enuff.

Oddly enough, the engineer at our public access tv operation said
essentially the same thing regarding their new cameras; they don't do
any setup or adjustments other than the TLAR of flesh tones on talent
in the studio. They also route all of the new cameras through frame syncs
and proc amps so that is where all of the adjustments are done (is that
where it is all headed - no more camera setup?)

Between the cameras and the transmitters there are likely to be a
considerable number of pieces of equipment dedicated as auto-level
compensators for various signal parameters.
At one time, the controls for these adjustments were probably the
responsibility of a broadcast station engineer, for the engineer to
monitor and adjust as required.

It's very interesting to play with a color corrector to adjust the
levels from different sources to get them to look nearly identical.
For a small-scale production setup, I would think that a color corrector
would be an absolute necessity.

See comment above regarding the no-setup approach.

In the movie industry, many varied shots are made with vastly different
equipment, sometimes by choice and other times by necessity.
I watched a director explain that anything from 8mm film, various types
of video, and high-end wide film are sometimes combined to create a movie.
In another example Spielberg(?) was explaining that the color levels
were intentionally reduced in Saving Private Ryan, and when the movie
made it's way to cable, the program providers were swamped with phone
call complaints that the colors were too weak, so the providers adjusted
the levels. OK, TLAR.

I suspect that much of the final product is corrected by specialized
computers in most movie and TV productions.
Viewers might expect a different level of color rendering for a product
such as a nature film where everything should look natural.

<snip>

Michael

 

[Richard Crowley]

"msg" wrote ...

I found the gray scale reflectance chart at our public access tv
operation and checked it out for a few weeks to permit attempts to
duplicate it. Indeed it uses 'chips' (swatches) of continuous tone
pigment pasted onto a uniform background. The center square is still
a bit of a mystery; on this chart, it is a piece of black velvet
fabric.

Yes. The black velvet fabric provides a completely NON-reflective
spot so that you can use a waveform monitor to see where the black
level is coming out of your camera. VERY handy.

Television Test Charts should be handled carefully and protected from
undue
exposure to strong light, which can fade the colors and reduce their
usefulness. Charts have an average wear-out life of two years, after first
use. This chart should be replaced not later than --Feb 1988--
----------------------------------------------------------------------------

Now, it's off to the paint store...

You have a chart that is 21 years out of date. If you match paint
colors to it, you will have a copy of a 21-year expired chip chart.
Do they not have a current chart?

 

[Richard Crowley]

"msg" wrote ...

I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

It is not clear to me how aiming a camera at a graphic image of
color bars can be used for calibration of any kind? How were
you going to use this?

Colorbars are typically generated by a binary counter with
the least significant bit ("1") driving the blue channel, the next
bit ("2") driving the red channel, and the most significant bit
("4") driving the green channel. Known amplitudes (75%,
100%, etc.) are fed into the color encoding circuit to allow
the encoder to be calibrated.

The imaging devices, lens, and lighting have no role in this
part of a camera calibration. Trying to calibrate the encoder
with color bars coming through the lens and onto the imaging
devices is like trying to solve an equation with two (or more)
unknowns.

2. Luma staircases, 12 step, consisting of two horizontal bands of
opposite gradient separated by a central square (of some unknown
value) as provided by Panasonic gray scale chart VFKS003A (reflective)
and VFKS002A (transmissive). (Anyone have access to this chart or
something similar to describe what is in the center?)

The grayscale ("chip") chart is used for fine adjustment of the
analog parts of the imaging devices before the signal goes into
the color encoder. The color encoder must have already been
calibrated (with the electronically generated color bars) or else
the next step is futile.

After the encoder is calibrated, one adjusts gain, offset, gamma,
knee, etc, etc. (whatever is available in the camera electronics)
so that red, green, and blue all track perfectly in order to make a
perfectly colorless (zero chroma) stairstep on a waveform monitor.

This was the Google's first hit searching for: TV chip chart
http://www.kozco.com/ This guy has both grayscale ("chip")
and colorbar images for what its worth.

Could one conceivably make color test charts using paint swatches
from the paint store? Would a commercial standard chart, brought
into the store to be scanned by the in-store spectrophotometer,
be necessary to do the matching? If so, perhaps I can check out
such a chart from the local public access TV folks.

If you are adjusting the colorimetry of the R, G, and B channels,
then the exact value of the gray chips doesn't really matter. In
fact, using a continuous ramp would serve the same purpose (i.e.
getting the RGB channels to track perfectly.) The exact value
(reflectance %) of the gray chips DOES matter when making
absolute calibration for gamma. It also assumes that you have
a waveform monitor to view the video signal with.

Thanks for any insights; I just cannot afford the high costs of
commercial charts.

What are you calibrating? Do you have a calibration procedure
which calls for a graphic image of color bars? Seems rather
unconventional (not to mention difficult) to me.

 

[Mike Kujbida]

Richard Crowley wrote:

A whole lot of really good stuff which I don't need to repeat.
In my former life, I was a studio tech and spent (way too) many hours
doing alignment on 3-tube cameras.
All I ever used was a properly lit 10-step black & white chip chart in
combination with waveform & vector monitors and an oscilloscope.

I sure hope that the OP has no intentions of trying to properly match
the luminance values of a chart that's more than 20 years old as it
ain't gonna happen.


msg wrote:

Oddly enough, the engineer at our public access tv operation said
essentially the same thing regarding their new cameras; they don't do
any setup or adjustments other than the TLAR of flesh tones on talent
in the studio. They also route all of the new cameras through frame syncs
and proc amps so that is where all of the adjustments are done (is that
where it is all headed - no more camera setup?)

Sad but true. The days of studio techs (especially in low budget
places) actually giving a damn about technical quality is rapidly going
the way of the dodo bird.
My experiences lately have been that most of them don't know what to do
with the bars & tone I put on the head end of a tape :-(


Mike

 

[ushere]

Mike Kujbida wrote:

Richard Crowley wrote:

A whole lot of really good stuff which I don't need to repeat. In my
former life, I was a studio tech and spent (way too) many hours doing
alignment on 3-tube cameras. All I ever used was a properly lit
10-step black & white chip chart in combination with waveform &
vector monitors and an oscilloscope.

I sure hope that the OP has no intentions of trying to properly match
the luminance values of a chart that's more than 20 years old as it
ain't gonna happen.


msg wrote:
Oddly enough, the engineer at our public access tv operation said
essentially the same thing regarding their new cameras; they don't
do any setup or adjustments other than the TLAR of flesh tones on
talent in the studio. They also route all of the new cameras
through frame syncs and proc amps so that is where all of the
adjustments are done (is that where it is all headed - no more
camera setup?)


Sad but true. The days of studio techs (especially in low budget
places) actually giving a damn about technical quality is rapidly
going the way of the dodo bird. My experiences lately have been that
most of them don't know what to do with the bars & tone I put on the
head end of a tape :-(


Mike

now there i was thinking bars and tone was slang for a pub crawl and the
associated noise, and at the head was where it ended up ;-)

 

[Mike Kujbida]

ushere wrote:

Mike Kujbida wrote:
Richard Crowley wrote:

A whole lot of really good stuff which I don't need to repeat. In my
former life, I was a studio tech and spent (way too) many hours doing
alignment on 3-tube cameras. All I ever used was a properly lit
10-step black & white chip chart in combination with waveform &
vector monitors and an oscilloscope.

I sure hope that the OP has no intentions of trying to properly match
the luminance values of a chart that's more than 20 years old as it
ain't gonna happen.


msg wrote:
Oddly enough, the engineer at our public access tv operation said
essentially the same thing regarding their new cameras; they don't
do any setup or adjustments other than the TLAR of flesh tones on
talent in the studio. They also route all of the new cameras
through frame syncs and proc amps so that is where all of the
adjustments are done (is that where it is all headed - no more
camera setup?)


Sad but true. The days of studio techs (especially in low budget
places) actually giving a damn about technical quality is rapidly
going the way of the dodo bird. My experiences lately have been that
most of them don't know what to do with the bars & tone I put on the
head end of a tape :-(


Mike

now there i was thinking bars and tone was slang for a pub crawl and the
associated noise, and at the head was where it ended up ;-)

Watch it there 'kid' or the price for that Windows 7 package of yours
will mysteriously double

Mike

 

[msg]

Richard Crowley wrote:

"msg" wrote ...
I would appreciate suggestions and success stories from anyone who
has printed (or otherwise made) some standard video test charts for
camera setup; I need to make at least the following charts:

1. Full height color bars, 75% and 100% saturation;

It is not clear to me how aiming a camera at a graphic image of
color bars can be used for calibration of any kind? How were
you going to use this?

Colorbars are typically generated by a binary counter with
the least significant bit ("1") driving the blue channel, the next
bit ("2") driving the red channel, and the most significant bit
("4") driving the green channel. Known amplitudes (75%,
100%, etc.) are fed into the color encoding circuit to allow
the encoder to be calibrated.

The imaging devices, lens, and lighting have no role in this
part of a camera calibration. Trying to calibrate the encoder
with color bars coming through the lens and onto the imaging
devices is like trying to solve an equation with two (or more)
unknowns.

<snip>

Calibration procedure calls for the following in this order:

Adjustment Chart
1. AGC Grayscale
2. Pedestal Level Grayscale
3. Output Level Grayscale
4. Carrier Balance & R-Y, B-Y Pedestal Grayscale
5. White Balance Grayscale
6. Auto White Balance Grayscale
7. Auto White Balance 5500 deg. Grayscale+filter
8. Color phase + R-Y, B-Y gain Color Bars
9. Hi Inten Surpress/Backlight Comp Grayscale
Plus a bunch of adjustments of digital effects section
using fabricated Red/Blue, cross, box and other charts.

The electronics doesn't generate color bars and the phase and
gain adjustments are done by shooting the chart.

Michael

 

[Dave Plowman (News)]

In article <7cpvbpF298l2pU1@mid.individual.net>,
Mike Kujbida <kXuXjXfXam@xplornet.com> wrote:

Oddly enough, the engineer at our public access tv operation said
essentially the same thing regarding their new cameras; they don't do
any setup or adjustments other than the TLAR of flesh tones on talent
in the studio. They also route all of the new cameras through frame
syncs and proc amps so that is where all of the adjustments are done
(is that where it is all headed - no more camera setup?)

Sad but true. The days of studio techs (especially in low budget
places) actually giving a damn about technical quality is rapidly going
the way of the dodo bird.

Whilst this is true, there simply isn't the need to line up modern cameras
in the same way as of yore. They do it themselves in software. There is,
however, still the same need to match them by eye using a decent monitor.
Which can be a problem since CRT monitors are near obsolete, and LCD are
near useless for this.

My experiences lately have been that most of them don't know what to do
with the bars & tone I put on the head end of a tape :-(

Again these days the pictures and sound are simply 'digitized' straight
into the editor. But that bars and tone can be useful if there prove to be
subsequent problems - if only to cover your arse. I'm using Panasonic P2
these days which records to memory cards - and due to the cost of these
get re-used the next day after digitizing the contents - so there is no
way to refer back to the original line up, unlike tape where they will
usually be kept at least until the edit is finished.

--
*Bigamy is having one wife too many - monogamy is the same

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[none]

The only home-brew test charts I know to work, are focus charts and
black level chart (a small square or rectangular hole cut into a large
sheet of flat white card-stock, backed by a box lined with dull black
felt or velvet, so any light entering the hole is unlikely to escape).

The best advice I can offer you, if you have more than one camera, is to
choose the one that appears to produce the truest colors, and adjust the
other(s) to match.

It won't be right, but it won't jar the viewer's sensibilities quite so
much when you switch between cameras. In a pinch, it'll get you through
a remote-van live-shot.

 

[Richard Crowley]

msg wrote:

Calibration procedure calls for the following in this order:

Adjustment Chart
1. AGC Grayscale
2. Pedestal Level Grayscale
3. Output Level Grayscale
4. Carrier Balance & R-Y, B-Y Pedestal Grayscale
5. White Balance Grayscale
6. Auto White Balance Grayscale
7. Auto White Balance 5500 deg. Grayscale+filter
8. Color phase + R-Y, B-Y gain Color Bars
9. Hi Inten Surpress/Backlight Comp Grayscale
Plus a bunch of adjustments of digital effects section
using fabricated Red/Blue, cross, box and other charts.

The electronics doesn't generate color bars and the phase and
gain adjustments are done by shooting the chart.

Sounds like a low-end one-chip consumer camera.
In which case it likely isn't terribly critical.

 

[MG]

Oddly enough, the engineer at our public access tv operation said
essentially the same thing regarding their new cameras; they don't do
any setup or adjustments other than the TLAR of flesh tones on talent
in the studio. They also route all of the new cameras through frame syncs
and proc amps so that is where all of the adjustments are done (is that
where it is all headed - no more camera setup?)

(extra stuff snipped)

That might be true at your local public access station, but public access is
not exactly noted for its technical quality, and I can assure you that in in
the commercial broadcast field, cameras are still set up rigorously, and
anyone that would rout everything through frame syncs as a matter of
standard practice would need to find a field other than system design to
work in. Cameras are referenced and timed as always.

The gray scale chart is used because it allows the VO to match all the color
channels in a number of parameters. Scopes (waveform and vector) are used
to take the color variations of monitors out of the equation in the initial
setup. High-precision video monitors (ideally CRT but, sadly, LCDs are
working their way into this, and so far they don't compare) are then used
for final painting.

In many ways, nothing has changed in video control since color cameras
became the norm.

mg