Cross Platform Gamma Issues

[Darby Edelen]

Well I’d have to say that they’re rendered with different gamma encoding, but you already knew that =)

Why don’t you render them using a uniform working color space?

[Tracy Westgard]

Are you using a scope to compare your images??

[Bryan Everett]

Please elaborate on uniform working color space. I’m working in 8 bit per pixel color space on both MAC and PC.

[Bryan Everett]

Yes, scope in FCP as well as importing both a PC frame and MAC frame back into AE on either platform and using the AE info window to view the RGB values of the sampled pixel, which really isn’t necessary because they are visible quite different.

[Darby Edelen]

Go into Project Settings (ctrl-alt-shift-k, cmd-opt-shift-k) and make sure that your Working Space is set to something other than none (what depends on your final output: Adobe RGB should be fine for most purposes, you could use SMPTE-C if you’re going to be viewing on a TV).

I believe that if you don’t specify a working space AE will just use your computer’s gamma value when encoding, which varies widely from platform to platform (and from computer to computer).

[Bryan Everett]

I went in and set both PC and MAC to use SMPTE-C for the working space and rendered the same Grayscale Bars on both.
I’m getting the same varied results. White and Black stay the same at their respective 255 and 0 but everything in between shifts greatly.
When I bring my MAC render back into AE (on the mac) my mid Gray value remains at 127. When I bring the PC render into my MAC comp to compare the 2, the mid Gray (which started at 127) is now at 97. A whole 30 point luminance shift. However, on the PC side, if I bring my PC render back into my PC comp, the PC luminance values are dead on and when I bring my MAC render into the PC comp to compare, the MAC mid gray value (127 pre-render) is now 155. A 27 point luminance shift. I have opened both renders up outside of AE and compared in QT Player which yeilds the same VERY visible difference. I can’t figure out if this is an AE issue, a QT issue, a platform issue or all of the above.

[Danny Princz]

what codec are your rendering to?

who is that masked man…

[Darby Edelen]

[pkpictures] “I went in and set both PC and MAC to use SMPTE-C for the working space and rendered the same Grayscale Bars on both.
I’m getting the same varied results.”

That’s strange. I looked to the AE help for more information on Color Management and the only explanation I can come up with is that you need to use the same Color Profile for the displays you’re rendering from, i.e. sRGB (it shouldn’t have to be the same as the AE project’s though).

A few excerpts from the help:

“When After Effects displays pixels, it converts from the working color space (which characterizes the space colors are in) to the monitor profile (which defines how the monitor reproduces color) to produce predictable, consistent color.” (It wouldn’t make sense to me for the render to take the monitor profile into account, but maybe?)

“Because After Effects doesn

[Grant Lovering]

I found a similar issue when converting something graded in HD to SD. We are using a Kona system and it came down to the Apple Uncompressed 10-bit codec as the problem. We found by using the codec supplied with the kona drivers v210 it solved our problems. One thing you need to do though is enable AE to see this codec. There is an FAQ on Kona’s site about how to edit the preference so AE can access it.

Hope this is helpful and if not, might lead you to the problem.

[Steve Roberts]

Indeed, it may be the codec. Have you tried rendering to a TGA sequence? (which you may be doing)