Banding issues

[Jer25]

I'm having problems with my images banding and can't figure out why.
I tried cranking the settings, changing the lighting, creating new materials and even made a new scene. I'm getting this problem in every scene now.

The first attached image displays the V-Ray frame buffer banding and a clone to the max buffer. The second image is with max's fb, and doesn't have the problem until it is saved. Possible because of it's brightness?

Another thing that is acting strange is that V-Ray FB saves the image as it appears. If I render with max or clone to max and save, the image will save darker.

I haven't messed around with my gamma settings or anything. I did however update my nvidia driver. Is it possible that's messing it up? (I though it was working properly since then but I'm not 100% sure).

My system gamma settings color mapping are attached as well.

[Paul Oblomov]

Maybe it all about clamping. Turn it on in vfb.

[Jer25]

Maybe it all about clamping. Turn it on in vfb.

No luck.

[dlparisi]

I'm not exactly sure why you're getting the banding in the VRay FB but the differences between the max fb, the vray fb and the saved images are all due to gamma issues. Since you have the max gamma set to 2.2 a cloned vray frame buffer to max's will never match. If I remember correctly, Vray's FB does not respond to max's gamma setting while max's does. So for your settings with VRay's gamma set to '1' the Vray FB is actually showing an incorrect or linear image. In order to view it correctly you need to click the "display colors in sRGB space" button at the bottom of the VFB (clicking this box will also mean the max and vray fb will match). When you click "clone to max FB" it copies the image but the max FB is gamma aware so it shows the image with a corrected 2.2 gamma (approx. sRGB). When you save the max FB it's saving the image with a gamma of 1 while the frame buffer is showing it with a 2.2 gamma. You can specify the gamma if you like when saving the image.

I think I got that all right .

[dlparisi]

Maybe it all about clamping. Turn it on in vfb.

Exponential color mapping already clamps the output to 1. Not sure if it affects the internal calculations though.

[Jer25]

I'm not exactly sure why you're getting the banding in the VRay FB but the differences between the max fb, the vray fb and the saved images are all due to gamma issues. Since you have the max gamma set to 2.2 a cloned vray frame buffer to max's will never match. If I remember correctly, Vray's FB does not respond to max's gamma setting while max's does. So for your settings with VRay's gamma set to '1' the Vray FB is actually showing an incorrect or linear image. In order to view it correctly you need to click the "display colors in sRGB space" button at the bottom of the VFB (clicking this box will also mean the max and vray fb will match). When you click "clone to max FB" it copies the image but the max FB is gamma aware so it shows the image with a corrected 2.2 gamma (approx. sRGB). When you save the max FB it's saving the image with a gamma of 1 while the frame buffer is showing it with a 2.2 gamma. You can specify the gamma if you like when saving the image.

I think I got that all right .

Cool I've always been unsure if I actually grasped the gamma concept. I was doing that previously (sRGB button) but the whole image seemed a bit too washed out. I will go back to it after I figure out this banding issue.

For now I'm going to try and roll back the driver to see if that has anything to do with it. I'll let you know if I have any success.

[Jer25]

It was the driver update that was causing the problem. I just rolled it back and the images render and save fine. When I open up the previous images all but one have it removed. Honestly I don't understand why it would affect the rendered image but at least it's working properly for me now.

dlparisi - Should I be adjusting my images with the sRGB button on or off?

Thanks.

[dlparisi]

Assuming your monitor is roughly calibrated to a 2.2 or sRGB gamma, i.e., not linear (1) gamma, you should be previewing your images with the sRGB button ticked on. This is because you have the max gamma set to 2.2 and the vray gamma set to 1. If you set both gammas to 2.2 then the sRGB curve is burned into the image and you should be previewing it with it ticked 'off'. You need to watch your save gamma as well to make sure you open the images correctly in a image viewer or editor. Also kep in mind that the sRGB button only changes the display of the vray fb, it will save the same image regardless of the button setting.

I think the general consensus is that if you are going to work with linear images (like you are) that you are better off setting the vray gamma to 2.2 and checking the "Don't affect colors (adaptation only)" so that you get better sampling in the darker areas of the image.

Again, I think I got all that right - sometimes I get confused and start mixing gammas ...

[Jer25]

Thank you that's cleared up a lot for me.