Changing F-number in Curve editor also changes EV value

[MikkoK]

Hi

I'm not sure if this is a 3ds Max or V-Ray related problem, but I usually use the Curve Editor to animate my scenes. Now, I'm trying to animate the VrayPhysicalCamera's F-Number in the Curve Editor, but it's also changing the camera's EV value. The EV value doesn't change if I animate the F-Number from the Modify panel. I have Exposure set to Exposure Value, so it shouldn't change when I adjust the F-Number.

Thanks
Mikko

[hermit.crab]

Doesn't seem to happen on my end. Mind if you attach the scene?

[MikkoK]

Here you go. It changes the ISO value also (probably that's why it changes the EV value).

[hermit.crab]

Thanks for the provided scene. The difference in exposure is caused by the "lens breathing" effect (read more here). It will happen even if you leave only the Focus Distance keys. No way to disable it at this point, though we do have an improvement request logged for it (internal bug-tracker id: VMAX-14382). A workaround may be to use the 3ds Max native camera, which does have the Lens breathing parameter exposed.

[MikkoK]

Okay, thank you! But why does this happen only when I'm modifying the values in the Curve editor?

[Joelaff]

Actually, Lens Breathing, both exposure and focal length changing are disabled when you use FOV instead of Focal Length, and disable Exposure control (adjust your light values instead).

We would all like a simple checkbox to turn those effects off though so we can still use EV and still use focal length without having to think about such real world limitations.