How to make lens effects only affect certain objects, not the background image?

[onyxlee]

Hello guys, I have a scene with a background image. When a bright object with vraylightmtl properly generates lens bloom, how do I prevent the bright pixels in the background image from generating lens bloom? (adjusting threshold def doesn't do the trick. I would assume that an object with vraylightmtl is really hot in the exposure histogram, while a white pixel in the background image is just white. But when it comes to bloom, they are treated the same.)

Another thing is, how do I only allow ObjectID=x or MaterialID=y to generate bloom, while ignore other objects or material? Ideally I won't want to deal with the bloom in After Effects.

Thank you.

[hermit.crab]

If you're using an HDRI image, it surely has pixel values above 1 in the brightest of spots, causing the lens effect. You could clamp the HDRI (VRayBitmap>Output>Clamp), this would yield maximum pixel values of 1.
Sorry to say, there aren't object/material id masks with the V-Ray Lens Effects since the effect functions as a post-process, applied to the whole image (based on pixel values).

[onyxlee]

Thank you, hermit.crab. Yes, the background image is a JPG, so I just need to hover my cursor above those white (but not bright) pixels in the JPG and get a reading, then put that number into the threshold, this way I can successfully exclude those white (but not bright) pixels from glooming.

Thanks again.