Saving multiple exposures from VFB in Vray 5

[Nicinus]

How do I save my VFB modifications into the image? I thought the way to save these were via effectsresults, but this channel does not show up if you just make an exposure adjustment. It is not available as a renderelement either, so I'm obviously missing something obvious here.

I'm doing interior renderings where there are large windows of the garden in the background, and as everything in this garden is modeled, I basically need to combine two exposures to have proper exposure both inside and out. I don't want to render twice though if I can avoid it, and since it is about two stops I think it is good enough to compensate with VFB exposure. (Is there a quality difference between decreasing the camera 2 stops, vs adjusting exposure in the VFB the same?)

Grateful for all advice / tips.

[matanov]

Just use the Save icon?

[ThomasMiller]

It is not available as a renderelement either, so I'm obviously missing something obvious here.

Are you sure you're checking the box on top of the exposure control in order to apply the changes to the images? These corrections should apply to the RGB Color main render element, not just to effects result.

[Nicinus]

Hi Thomas, I don't have that button, this is in Vray 5

[Nicinus]

Ehem, now it actually seems to work without issues. Embarassing, but not sure what I did earlier.

[ThomasMiller]

Hi Thomas, I don't have that button, this is in Vray 5

Sorry Nicinus! My oversight. My brain completely ignored your "in V-Ray 5" in the title. Glad you got it to work in the end!

[^Lele^]

(Is there a quality difference between decreasing the camera 2 stops, vs adjusting exposure in the VFB the same?)

There are, yes.
Adaptation (for anti-aliasing) is done on the visible part of the image (you can see it happen if you watch a SampleRate RE while rendering progressive).
So there will be a difference in rendertime (brighter -> slower to converge).
And conversely, there will be a difference in noise levels: twice as bright, in post, will also be twice as noisy (and vice-versa), as the multiplication acts on both noise and signal, widening the absolute gap between the two.
The SnR stays constant, though, so perceptually the issue isn't as pronounced, often enough, as it is with measuring.

[Nicinus]

Thanks Lele

[jromero]

Any suggestions of what would the workflow be. How can I save two exposures when the job is rendered to backburner, not locally? I do not want to render twice with the two different exposure.

[^Lele^]

Perhaps load the image in the VFB a second time, and expose again?

[jromero]

lele Yeah man that workflow works for what i need. Vrimg kept all the overexposed color information. I can reload the vrimg in the vfb and adjust a second exposure without re-rendering!

[^Lele^]

EXR should work as well.