Saved render images have incorrect gamma

[philvanderloo]

My rendered frame buffer image is correct but the saved .jpg or .tiff is too light. (as if show srgb colors was ticked in frame buffer).

In my searches I have found a fix to be to change the program default render output gamma to 1.0. But when I open the notepad file in program files, I am unable to save it after changing outputgamma. Getting access denied even though I'm logged in as admin.

Tried clicking on notepad icon and choosing run as administrator but it's still not allowing me to save.

two questions-

1. Am I on the right track or should I be checking other render/gamma settings.

2. If I am on the right track can someone show me how to get around the "Access Denied" issue

I'm in Windows 7 64 bit. My input gamma is set to 2.2 in max but max 2015 doesn't allow me to change output gamma without going to the default text file in program files.

[philvanderloo]

Ok I figured out how to save the output gamma to 1.0. But still wondering if this is the right solution or if I can expect other issues from this. Haven't checked yet to see if saved render images are ok now but just wanted to call the dogs off on the "access denied" issue.

[Scott Schroeder]

Ahh Max's brilliant auto-gamma.

 

Try this script, it should work in 2015. http://www.scriptspot.com/3ds-max/scripts/gamma-settings-for-3ds-maxdesign-2014

[philvanderloo]

Thanks Scott. I actually got this to work

[philvanderloo]

Well I thought I had it figured out but I don't.

Can someone get me headed in the right direction on why my saved rendered images have a different gamma than the image in the frame buffer.

This project always saved fine before. Not aware of anything I changed to make this happen.

My system gamma is set to 2.2 input, and 1.0 output gamma. Was getting the same result

with both set to 2.2

 

[Ismael]

http://forums.cgarchitect.com/74756-clone-vray-frame-buffer.html

[jasonstewart]

Ah the age old struggle of gamma correction. I am not an expert and I have just found someones setup and used it so take this info with a grain of salt.

 

You are baking the 2.2 Gamma curve into your renderings by setting the gamma in Vray options to 2.2. Without checking the srgb curve option in VFB you are seeing it with 1.0 Gamma curve so when you save it you now see it in 2.2 and all of a sudden it looks too bright/washed out. So you can either spend a bunch of time redoing all your lighting/materials or just apply the inverse gamma curve of .4545 in PS to correct your render to what you are seeing in the VFB. If you check the show in srgb space button you will see exactly what you are seeing in the final image.

 

Its a hard thing to get good info on because if you look at a tutorial from a couple years ago the information will be different than today.

[philvanderloo]

Ya, thanks Jason and Ismael. I think I have some clarity on it now. I changed a few light settings, the camera aperture and all is ok now.

What gets me though is why the default system gamma is set to 2.2 input and 2.2 output when it seems almost everyone prefers 1.0 output. And in 2015 it's not a quick change. See Scott's reply.

Wonder why they took out the input/output gamma settings starting with 2014?

[jasonstewart]

I believe that most people are saving out 16 or 32 bit exrs so output gamma is a moot issue. That would be another solution to try but I believe even that would be at the sRGB level and would require post processing to fix.

 

Its definitely something I would like to understand better but with changes to the software like you mentioned combined with LWF changes over time it is something that is hard to grasp. I will say that I get more realistic results with 2.2 gamma and show in sRGB space checked so unless my method is shown to be wrong I think I will stick with it. I think you should play around with that scene and see what appeals to your eye (I believe you have said that all your renderings are for your own projects so you dont have a client to please) since the final image must be what you have tried to create. Try both ways and figure out what is your desired look.

[Scott Schroeder]

Autodesk has decided to play, we know what's best with the gamma. So Jpeg images are generally forced towards 2.2 where as exr's are forced towards 1.0. Max will decided, based on the image file output, which gamma to apply. Needless to say, folk's wasn't happy with that.

 

The other item to watch out for in Vray is the "mode" for your gamma in your color mapping section. If you are saving to 2.2, and you set your Vray gamma to 2.2, you'll want to set it to "color mapping only (no gamma)". Vray will sample the image as if 2.2 is being applied, but output the image without double correcting the gamma. As is my half-baked understanding of it all.

[RyderSK]

In 2014 this is just generally error on 3dsMax internal (no longer exposed) auto gamma output incorrectly guessing it for your saved file.

It's nothing to do with all the Vray's gamma modes ( which are oddly confusing for most too and I can't blame them).

 

To be always on save side, even if it's annoying, save your file with "override gamma" checked on when saving the file to disk, and manually type in 2.2 for every single file format (jpeg,tiff,png) except for hdr/exr (which are 1-linear).

 

 

--------------------------------

Side-topic: To clear some of the above gamma confusion, few users mentioned:

 

Vray 2.4.04 to 3.007

 

Max Gamma/LUT 2.2 for everything, output no longer exposed. Applies to all options bellow.

 

Vray's possible options:

 

1: "Traditional linear" - Gamma 1.0 Mode:NONE; Framebuffer SRGB ON {deprecated, no longer favoured}

 

2: "Modern Vray linear" - Gamma 2.2 Mode:NONE; Framebuffer SRGB ON {samples based on 2.2, but applies 1.0 to result, benefit: cleaner highlights and shadows}

{{note2: this is former Linear/Don't affect colors, it's fully linear, but samples on any specified gamma}}

 

3: "Modern Vray Reinhard(or any other)/New Default" - Gamma 2.2 Mode: COLOR MAPPING ONLY; Framebuffer SRGB ON { samples based on 2.2 and Reinhard(or any other) curve, end result is 1.0 but color mapping is burned in, benefit: cleaner highlights and shadows, much faster rendering; cannot composite properly if Burn value

 

3B: Burned in Gamma version of the above, useful if you don't need 32bit linear output. Renders faster.

Instead of COLOR MAPPING ONLY, change to COLOR MAPPING AND GAMMA, and ticks SRGB OFF in framebuffer. Save as 2.2 TIFF/PNG (or any other).

Edited June 26, 2014 by RyderSK

[Tommy L]

http://www.neilblevins.com/cg_education/linear_workflow_vray_max/linear_workflow_vray_max.htm

 

The above is really simple.