Focus Distance + Zoom Factor

[yog]

There appears to be a bit of a bug when rendering with depth of field and using small focus distances.

Down to approximately 360mm on the focus distance the zoom amount on the Vray camera stays fairly constant and basically matches the Modo viewport.
The first image is with the focus distance set to 360mm and it matches the viewport.


However the next two images have the focus distance set to 70mm and 45mm respectively, and as you can see this appears to effect the zoom factor quite abit, although the Modo viewport remains constant.


Also there appears to be quite a large disparity between exposure level when using the RT renderer and the final renderer when combined with DOF and these small focus distances. The first three screen grabs were taken of the RT renderer, the fourth image with the same 45mm focus distance as the 3rd image, but is a screengrab of the full Vray render.

[vladimir.nedev]

The first problem is caused by the V-Ray physical camera modifying the focal length internally so the specified focus distance is achieved. And this in turn modifies the field of view in the rendering.
It should be fixable, I will write back here when it is.

The second one is probably due to the exposure not correctly updating in RT. If you restart the RT rendering you will probably see that the RT/final rendering match.
I will fix this as well.

Greetings,
Vladimir Nedev

[vladimir.nedev]

This is fixed for the next beta build. The rendered frame when using the physical camera will match the rendered frame without it.
The zoom factor of the physical camera no longer affects the field-of-view, only the depth-of-field effect.

Greetings,
Vladimir Nedev

[1funk]

Hi Vladimir. I noticed that even though you disabled the FOV from a changing due to lens breathing, the exposure still changes (gets darker) on small focus distances. Did you leave this in intentionally?

I don't think it makes sense to remove only half of the "lens breathing" effect. I would prefer the exposure darkening was removed too.

EDIT: The lens breathing is not mentioned in the modo docs (only the 3dsmax docs include any info on it), so this could also cause some confusion.

[vladimir.nedev]

That's just how the physical camera implementation works internally.
You can either give it a focal distance or specify the FOV. In the second case, it will search for the correct focal distance that achieves the specified FOV taking into account all other parameters.
We should add the missing stuff to the help though. The lens breathing is not the only thing missing.

Greetings,
Vladimir Nedev