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Maaahshoe
06-18-2009, 04:45 AM
Hi,

One question why have I been told to set gamma to 2.2 when using EXR format as the output?????? Can someone give me an explanation, thanks!



Matt

phix314
06-18-2009, 08:03 AM
Without getting too lengthy, 2.2 is the "normal" or "corrected" gamma curve.

playmesumch00ns
06-18-2009, 12:28 PM
Errr... what exactly do you mean by 'set the gamma to 2.2'? That could have a lot of possible interpretations, and the most obvious one, that it's applying a gamma of 2.2 to the image, is probably the exact wrong thing to do if you're intending to use those exrs in a linear compositing pipeline.

Maaahshoe
06-25-2009, 05:41 AM
Thanks for the replies. I read somewhere about using EXR format its best to set the Gamma within 3DSMAX to 2.2. Is it true the image holds lighting info that exposure can be adjusted after rendering? What you mean linear compositing pipeline?

Trauco
06-25-2009, 05:29 PM
"Is it true the image holds lighting info that exposure can be adjusted after rendering"

If you save your images as 32 bit float you can control exposure without damaging the image, because you can have values over 1. I use it mostly when i'm almost certain that i'm gonna get overexposed spots. Also works for underexposure, but for that i use the next option.

If you save your images as 16 bit int you can get values up to 1, it is useful if you get underexposed images, because you can open that 16 bit image on a 32 bit workspace and take the values that are at 1 and go higher. for overexposure it won't work because you don't have "superwhites" (whites that are over a value of 1)

Never used EXR format so i don't know what can be specific to it. (I've got plans to for my next project but i got to read the documentation first)

About the gamma i could point you to a really good explanation in spanish (http://www.efectohd.com/2008/09/entender-la-correcion-de-gamma.html) .

(...opening max at the moment)

Ok, if i understood what you meant by gamma 2,2. you are right.

go to Customize -> Preferences -> Gamma and LUT.

then go to the display box and check Gamma and set it to 2,2. (this also depends on the kind of monitor you have but i bet that like 80% of the world today you got a LCD monitor)

This only affects how you see stuff inside Max, you should not touch the output values unless you really understand what you are doing.

I hope that someone with a better domain of english can explain you better :-) good luck

PD: Shit! i was convinced i knew what i was talking about until i saw this thread (http://forums.cgsociety.org/showthread.php?f=2&t=610790) read it, and all the links (now i'm really unsure about what i told you, because it also depends on what are you using to render, for example MR photographic exposure control applies a 2,2 gamma correction, so you should not use the defeault gamma correction.)

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