Weired: Exposure depends on Target-tag

[steilvorlage.de]

Hi, in my testscene you find a cameraanimation with a target-tag, but no DOF. If you render you see, that the exposure is changing (getting black at the end) although nothing but the position of the camera is changing. If you delete the target-tag, the exposure is correct. Can you please check?
I checked with Vray 5 and 6.

Cheers
Tobias

[deyan.hadzhiev]

Hi steilvorlage.de, this is expected if the target tag changes the current camera focus distance (and physical exposure is used in the camera). This effect is explained in details here.

[steilvorlage.de]

Hi Deyan, which kind of focus is it, if not DOF? Focus with target-tag in this case just defines the angle of the camera. And I don't use physical exposure but exposure value.

[deyan.hadzhiev]

Hi steilvorlage.de, you need to clear the focus object parameter in the camera object - having the target tag on the camera will still control the angle, but without affecting the focus as well. Also please note that this behavior changed between V-Ray 5 and V-Ray 6. In V-Ray 5 the focus distance did not properly read the constant value when the focus object is cleared, and we fixed this in V-Ray 6.

[steilvorlage.de]

If I clear the focus object parameter in the camera object, nothing is changing, the sphere is still getting dark. Only by deleting the target-tag the sphere stays light. But I need the target-tag and I need animated DOF.

Thanks Deyan

[deyan.hadzhiev]

Are you using V-Ray 5 or V-Ray 6? As I mentioned, there was a problem with this in V-Ray 5 that we fixed in V-Ray 6.

[steilvorlage.de]

Right now I'm testing both versions. Please open the attached file. It's Vray 6. "Use target object" is active - nothing is visible. If you deactivate (the focusdistance stays the same - 6,524 cm) the object is visible. So only by activate/deactivate the button the exposure is completly different.

[deyan.hadzhiev]

Can you demonstrate the problem with a video? I tried with the scene and there is no difference with the "Use Target Object" parameter on and off (which is expected because use target object parameter calculates the focus distance to the target and updates the focus distance parameter).

[steilvorlage.de]

Do you know a workaround for the problem? I have products of about 5-10 cm and I need animated macroshots with DOF and nice lights.

[steilvorlage.de]

https://www.dropbox.com/t/yLnGpniWrzx9VkuO
Here is another one. You see that with using target-object, there is a point with no light (distance 6,524 cm). If you go near or more far away, there is light again.

[steilvorlage.de]

In this animation you can see very good, how the image is going completly black if there is a special focus-distance
https://www.dropbox.com/t/677sTKqn5nVfrMr4

[deyan.hadzhiev]

Hi, sorry for the late reply.

Do you know a workaround for the problem? I have products of about 5-10 cm and I need animated macroshots with DOF and nice lights.

As previously mentioned, this is the physical camera lens behavior and really low values decreases the exposure.
There are only two workarounds for this problem if you want to have consistent exposure with very near focus points:
1. Disable the physical exposure in the Physical Camera Tag.
2. Use automatic exposure override (Render Settings -> Overrides -> Camera -> Auto Exposure)