#Gamma
8 messages in this thread
I just completed the NTSC colorbars mesh file and spent some time
running some tests of the gamma adjustment and I made some
interesting discoveries. All tests done with tmode 11. Composite
video out. 1. The correct gamma setting for my system is indeed
2.2. The wash out effect I observed earlier on 3DS files was due to
a misunderstanding on my part of how gamma is applied in 3DS. Reading
pages 4-7 of the advanced user's guide it became clear. One must set
the input file gamma to the same value as the framebuffer setting so
that the colors in the 3ds file will be de-gammaed. Once I did this
and reloaded the file 2.2 no-longer washed out. Instead the detail
in the shadows was enhanced furtherthan before. 2. The gray boxes do
not work on my system. They still match up at 1.0. Which, when
coupled with input gamma setting produces much darker images. 3. The
vectorscope indicates that green is most affected in the picture by
gamma adjustment. The 3DS manual describes this also. Therefore,
adjusting gamma will shift the balance of color on an NTSC color
bar. I then was able to confirm that whatever the gamma setting you
input a file at you should render that same file at the same gamma on
the frame buffer to prevent color shift as well. The actual setting
is unimportant and can be set to whatever is yielding the best image
to personal preference. 4. I could find no adjustment 1.0 through
2.5 that made any color go illegal.
5. I did not do any tests of the output file gamma. By the manual it
appears that some experimentation is in order to determine this
number based on each output media eg. different type films, video,
and color print. The manual did say that print is linear but I have
my doubts. I know that the best prints I do on the canon BJC-800 are
those with some gamma correction.
Conclusion: The only negative I found is the gray boxes seem to be
totally useless on the targa+ in my system. They do work on the VGA
monitor. I have confirmed that 2.2 will work for excellent results
on my system too. The secret being to use the same input gamma
setting as the frame buffer setting when loading files for rendering.
Don – I'm very glad to hear that you solved the problem. It sounds as
though you aren't using a dedicated RGB monitor out of the Targa
board. A dedicated RGB monitor would enable you to use the
framebuffer gamma adjustment and the boxes would match. I use one
SVGA monitor for modeling, one RGB monitor out of the Targa for
rendering, and one NTSC monitor for the composite signal out of the
EVO. I also use custom switch boxes to share monitors with each
system. It works very well. And R3 and the Targa + is once again
vindicated! -JE P.S. Just had to throw that in there, didn't think
you'd mind. Anymore tough critics out there, talk to Don, I've earned
my wings 🙂
>> A dedicated RGB monitor would enable you to use the framebuffer
gamma adjustment and the boxes would match
So what you are saying is that the gamma adjustment using the gray
boxes only works if one uses an RGB monitor but not a composite
monitor off the frame buffer. I checked again for documentation on
this but couldn't find it in the 3ds manual. This is an important
announcement so could you elaborate? Is there some reason why RGB
works and composite doesn't on the gray boxes from 3DS gamma?
Not true. We've done tests with the gamma adjustment on dozens of
monitors (there are a lot of computers at Autodesk) and it works fine
on RGB, composite, and Y/C monitors. There's something unique and
bizarre about your rig that none of us are going to understand
without coming over to your house. (or, you could pack everything up
and fly out here to Autodesk with it… I'd be happy to meet you up
in San Rafael for lunch <g>)
I'm honored by the invitation but if Adesk is up to the cost of the
trip I'll contribute the time. <G>
Seriously, I didn't think for a moment that an RGB gamma display
should be any different than a composite ( one work/ one doesn't) It
just sounded that way from John's statement. Gary, I've looked at
the output on 5 different monitors now with several different setup
configurations for the targa+. tmode 11, tmode 25, tconfig with
several setup batches and tplusini method. They all match grays at
1.0. The VGA main display monitor at 1.8. The real common
denominator is the single targa+ board I have to work with. If I
could find someone else in Jacksonville with a 3DS3/video setup I
might be able to have something local to compare to. I'm sure you
read my results and it appears that the best looking picture is with
gamma set to 2.2 on both file input and frame buffer. With gamma off
shadows get lost in the dark areas such as the one in front of the
bumper of the chevy.3ds file. If I don't set the gamma to 2.2 on
input file and use 2.2 on the frame buffer the whole picture washes
out when I render.
I wish I could come over to your house and look at this setup. I have
a feeling that something still isn't right, because your grey boxes
aren't matching up. Too bad you don't live in SF…
>>I wish I could come over to your house and look at this setup. I have a
feeling that something still isn't right, because your grey boxes aren't
matching up. Too bad you don't live in SF…
Maybe DonL and I should pack up our stuff and meet you in Belize. Somehow
gamma correction wouldn't seem so important out there, tho'.
>>Maybe DonL and I should pack up our stuff and meet you in Belize. Somehow
gamma correction wouldn't seem so important out there, tho'.
Now you're talking. What's important in Belize? Sunscreen and a good air
compressor.