#STMPE bars
11 messages in this thread
I would like to create my own color or stmpe bars for use on the tapes that I
send out to post-production. I have been using the project file that I
retrieved from the board here, but I'm concerned about some possible problems:
1. I don't really understand how the post-prod. group uses the color
bars that I lay down at the beginning of our tapes, but I think it has
something to do with calibaration,
2. if calibration is being performed, I would like to generate my own
bars that are more representative of the work that I do – the bars project from
here isn't representative.
3. I like the stmpe version appearance over just color bars, because it
makes it easier for me to use my "blue" card and adjust my monitor.
4. Is there a really great, versatile NTSC library and palette, or just
a good set of rules of thumb to go by to better predict final output?
Thanks for your help!
Chris
Chris,
SMPTE bars were created to set a standard for color in the NTSC range for
RGBCYM. You can create your own bars but then they wouldn't conform to that
standard. As you summise they are for calibration. As video can have Hue
Saturation and Luminance adjusted, color bars provide a reference. The bars you
downloaded are fairly accurate and your work should be adjusted so that the
bars are a color reference not the other way around.
John
John, Are there any good reference materials on exactly How to use the color
bars? Also on using a WF monitor and Vscope?
Dave Mennenoh
David,
Tektronix has several terrific handbooks on test signals and monitoring devices
for free. They'll bring you up to speed on NTSC.
Bruce N. Goren
Thanks Bruce, I'll give Tektronix a call.
Dave Mennenoh
>> Are there any good reference materials on exactly how to use the color bars?
Also on using a WF monitor and Vscope. <<
Your AV supply place can probably get a hold of some manuals put out by
Tektronix, who make VS/WFM.
Also Neil Heller's "Understanding Video Equipment" ISBN 0-86729-184-2
Gary H. Anderson "Video Editing and Post-Production" ISBN 0-86729-257-1
Both published by Knowledge Industries Publ. In. White Plains NY.
They're not real technical and provide a good overview.
How's it going with the flying matte?
John
Thanks much John. I'll take a look into getting the books you mentioned. I'll
be testing the flying matte tomorrow. I'll let you know. BTW, when creating
mattes is it best to use super black or does it depend on the keyer being used.
Boy, so much to learn…
Dave Mennenoh
Thanks for you reply John, but I don't get it. Sorry.
What are the color values that are typically used in the generation of these
bars? How can I use them as a color reference for my work? Is there
additional information, somewhere, on really safe colors and palettes? I have
heard that NBC, for example, has spent many many dollars and years developing
working colors. Is information the goes into this type of thing available?
Chris
Chris,
First you need to talk with a video editor and have him explain how he uses
Bars to calibrate the video source (ie your animation or whatever.) If you go
into a paint package and read the values from each of the colors you can see
you maximum saturation and luminance values. On the other hand 3DS has a
built-in video color check which works well.
>> Is there additional information … on really safe colors and palettes?
If you stay below the max saturation and luminance values, you will be safe.
The rest is a matter of aesthetics. Highly saturated reds don't work but you
can get aesthetically pleasing reds that don't "bloom".
>> I have heard that NBC, for example, has spent many many dollars and years
developing working colors. <<
I'll check but this seems rather unlikely.
There are algorithms that are applied to an entire image to make them "color
safe" or "video safe". A program I use is by Elastic Reality which converts RGB
to YUV for output to D1. I've never had to worry about my colors, and the rest
is an aesthetic use of color. Some colors do work better than others but there
are so many combinations, I think it would be hard to define what works best
with what, though in print they have books with color combinations that are
aesthetic. You could use these as a guide.
John
Thanks for your lengthy response John. I really hate to keep pounding on this
horse, but…here are the specific problems I am having:
1. The bars I generate and drop to tape show wiggles at the magenta/red
interface. I notice these both on my monitor and I saw them today at a post
house.
2. We are really getting squeezed by our parent company on dollars for
animations. Our response has been to cut back to more psuedo-2D stuff. I mean
rather than moving parts and camera we do arrow reveals over a 3D hold, or just
go straight 2D. I have seen some bleeding and basically poor results when I
finally get to see an on-line. My first instinct is to blame myself and search
out possible solutions.
3. I generally knock all saturation values down to around 200-220, totally
avoid red, run gamma at 1.8, and on most straight 2D stuff kill all the
shinniness. Still, results that I'm not satisfied with when the on-line comes
back.
My question comes back to…"Is the calibration off at the post-house due to my
color bars?", and "where oh, where is that incredibly valuble *.mli file with
nothing but totally materials?"
Chris
Color bars come in two basic varieties, NTSC and SMPTE for NTSC video. Both
have the same colorbars but the SMPTE has additional color and luma calibration
bars. These bars should be generated by the same device as your program video
when recording to tape. eg. If shooting from a tube camera to a remote tape
recorder you would generate the bars from that camera. When shooting from a
chip camera you would generate bars from the chip camera. When generating
video from a PAR or frame buffer you would lay down bars from that video
source. In this way the bars (color reference standard) could be used to
calibrate the video timing just before recording and make allowences for any
deviation from standard at a different post facility. The bars that I uploaded
some time ago were intended to be used by those with a targa+. The PAR comes
with its own set.
Here's how I would use them in post. I receive an A-roll tape shot with a
camera and remote VCR. The bars look a little off and all flesh tones are on
the purple side. The magentas are orange. I have a B-roll tape that was shot
with a different camera and docable betacam deck. The colors look perfect and
the bars look good too. Next I pick up a tape of graphics done in an animation
post house which has bars generated by my "bars" file. However, they seem a
little shifted too. The yellows look green. In post I feed the bars signal
from each tape machine and adjust the chroma phase until each tape sends the
standard bars to my monitor making note of the adjustment for each tape. The
monitor sees the video signal just before and right after the edit VCR. Now a
particular Yellow will match on each tape when I mix the video in my A/B/C roll
edit. If the camera person were to record bars onto a tape from a signal
generator and then assemble edit the scenes in the camera the bars would not be
representative of the camera's signal. If you are not able to generate the
bars in the camera then shoot the bars from a test chart. Bottom line is that
the bars should follow the same signal path as the program video when recording
to tape.