gamma 2,2 - still don´t get it

[digitarch]

dear, very dear frayforum,
after reading the gamma treads and tutorials i still don´t get it (is it that complicated or is it me....).
I have:
- max presets gamma and lut: gamma 2,2 ; affect color selector and mat editor, input 2,2, output 2,2
- vray physicam, vray sun and sky, all default (disabled vignetting)
- vray color mapping exponentional, dark/bright/gamma = 1
- vray framebuffer srgb mode

now i put some boxes in the scene, apply 10 vray materials with EVEN steps of plain diffuse grey colors with values from 5 to 250.

I get a dark box with 50 and a bright box with 240 wich are ok to me, but i would expect the in between greys showing an even range from dark to bright.

But i get an biased scale from dark to bright where the 128 medium grey is sitting somewhere at 210 which gives me very few tones in dark and lots in the bright. The worst is i can´t trust the mateditor, i have to set medium tones somewhere at 25. This also dramatically affects greyscale mask, where i always have to set an "inverse gamma" curve in the output map.

how can i manage to produce an even scale to benefit from the whole range?
Matthias

[Dave_Wortley]

If you have the sRGB button enabled in the VFB make sure that "Don't affect colours" is ticked in the colour mapping options.

[MoonDoggie]

Your new 50% gray is at 49 on the value scale. That's just how it is now instead of 128 like you're used to. You can trust the material editor, if it looks like that in the mat editor (on the shader ball) it will render like that.

If you want to work with colors a bit more like the old way, apply a "VRayColor" to the diffuse slot of your materials, and at the bottom select "Specify" for the gamma and set it to 2.2, then select your color. It will be correct and what you're used to.

-Colin

[Morbid Angel]

some people do not understand that when you are working in linear workflow, the whole gamma 2.2 thing is for a display only. So once you start setting your output image gamma to 2.2 you are messing up everything. If you really wish to work in linear, you must render to exr (float) format, where basically images come out dark, and you click the sRGB button to just view them "brighter" thus viewing them in gamma 2.2

[MoonDoggie]

PS, it's not just you. Judging by the number of LWF posts...

[MoonDoggie]

Agreed, the correct workflow would be to set your max lut preferences to output gamma: 1.0 (linear), and save as .exr

[RichardBlank]

I am new to Max, but working in linear the "correct" way in Max will make the color selector useless?

[MoonDoggie]

No. Adjust values visually just like usual. It just changes where the colors are on the value slider.

[lukx]

but to save correctly to exr you need to render with Don’t affect colours (adaption only) checked right? When I'm rendering without it and saving exr it's adding extra gamma correction.

[peprgb]

but to save correctly to exr you need to render with Don’t affect colours (adaption only) checked right? When I'm rendering without it and saving exr it's adding extra gamma correction.

Yes and yes

[MoonDoggie]

Vlado,
I'd like to formally propose the following:

1. Make the "Linear workflow" button be a one stop shop to setup linear workflow in 3dsmax. (it could easily setup the max gamma/lut settings) and force someone to save an exr. As a side note, just have "Don't affect colors (Adapatation only)" be still there and everything else gray.


Preface: Not trying to be a jerk, however...

As a side note: there's lots and lots and lots of threads in this forum about LWF as well as online:

http://www.chaosgroup.com/forums/vbu...near+work+flow
http://www.chaosgroup.com/forums/vbu...near+work+flow
http://www.chaosgroup.com/forums/vbu...near+work+flow
http://www.chaosgroup.com/forums/vbu...near+work+flow


I'm all for people learning LWF (I did, and use it a lot). But I get the sense that people are more confused by the discussions of LWF than actually the using of LWF.

What I suspect is happening (because it is rather confusing, til you try it), is people are reading about LWF and they find out that it changes the midpoint of 50% (or whatever) and instead of just testing it in max with a teapot and a box, they're actually confusing themselves much more by posting on the forums and getting a lot more information than they really need at that moment (I'm very guilty of this). It would take less than the amount of time to post on the forums and wait for a response, than to try it.

Think back when you weren't using LWF. How did you figure out what some of the exposure settings in max did? What the correct color is for a refractive glass? What was a good value for a "satin"-like glossiness?

You tried them. You looked at your green color in the refractive amount and rendered and said "holy crap...that's too green", and you desaturated it.

I'm suggesting to new users of LWF to not "perfect" the technique (you might not even be using it to composite, which is the main reason imo). Just get results you're happy with and make your work look better. The best artists I know care very little about LWF unless (after thoroughly testing and perfecting) the technique, it is a means to a better result.

[RichardBlank]

No. Adjust values visually just like usual. It just changes where the colors are on the value slider.

What I mean is that the color selector in max is made for sRGB and it's impossible to make subtle changes near black when working in true linear. Doing gradients and working with ramps is also impossible in linear in Max. What exactly is wrong with the linear workflow button? Because I can't find a way around it.

[Zdravko]

If you decide to use 3ds max LWF approach it will be best to leave the V-Ray Color mapping settings by default (http://www.spot3d.com/vray/help/200R...lormapping.htm) this way you will know that V-Ray will not add additional gamma correction to your output and you will only work with 3ds max Gamma and LUT settings.
In case you decide to use VFB with that LWF approach you need to enable the sRGB button so you can see the output with applied gamma just like in 3ds max FB
Note that by using 3ds max LWF the Color selector window gamma will be shifted as well (respectively the black(dark) colors will be pulled toward the end of the gradient scale). This is done in order for the chosen colors to be represented correctly in the output. But this might lead to discomfort when choosing dark colors as you already mentioned

which gives me very few tones in dark and lots in the bright.

Therefore another LWF approach that you can use is to disable 3ds max Gamma and LUT settings and use V-Ray Gamma instead.

[henning]

What I don't get is that sRGB != gamma 2.2 (http://en.wikipedia.org/wiki/SRGB). So if we're telling max to use gamma 2.2 on sRGB bitmaps its only an approximation into linear, not exactly the correct way, right?
In Fusion when I comp in linear space I read sRGB images through a gamut node specifically interpreting it as sRGB.
Or doesn't it matter anyway? It seems so.

[glorybound]

the reason I think there is so much confusion is because I have seen 100 ways people are doing it. I found something that worked for me, and I stopped being concerned about it. I made the mistake of following a youtube yesterday, on the "correct way" to use LWF in V-Ray, and it was so wrong, and will confuse the heck out of people.

http://www.youtube.com/watch?v=hM1DVYiQuRs