Arnold Object Mask pass renders are not solid white

[war72]

Generally, when rendering an AOV with an Arnold Object pass (via .EXR file), the result is a solid white. However, I have a project that is giving me a grey result for all of my Mask AOV's - here's an example: 

I've cross-referenced my output/.EXR settings (32bit) and Arnold Object Mask tag properties with other projects that produce a clean white result and can't find any differences. Any ideas what could be happening? 

[peter_horvath · Accepted solution]

Camera exposure maybe? Do you have any imagers in the scene? What if you add an Arnold EXR driver, does it also produce a grey output? Does the IPR window display the AOV as grey too?

[war72]

The Camera exposure was the culprit. Confusing as the camera exposure doesn't affect the AOV in the IPR, only in the final render. Thanks Peter! 

[peter_horvath]

If you turn Blend Opacity off in the object mask tag, then the AOV won't be affected by the camera exposure. But it won't be affected by cutout opacity of the standard surface either or any type of opacity.