How to add alpha to EXR

[romullus]

I have few photo-light exr which have black border. It looks bad in reflections, so i figured out that i could make opacity map, so the border become invisible in render. I painted mask in Affinity Photo, saved the file as exr with alpha channel and loaded it in Corona light material. It kinda works, but the problem is, that as soon as i enable opacity, the exr in light material becomes much more contrasty and significantly brighter. If i save opacity map as separate 8bit file and load it into light material's opacity slot, then it works perfectly and doesn't affect contrast, nor brightness. The problem with this method is, that now i have 2 separate files and i don't like it for several reasons. Now the question - am i doing something wrong in how i author and save exr with alpha, or it's Corona that handles that alpha channel incorrectly?

[Aram Avetisyan]

Some screenshots or renders showing the difference would be helpful.
For using just one map - did you try using different Alpha modes for the light texture, in Channel outputs for Bitmap/CoronaBitmap?

[romullus]

Sorry, i've should provide more information indeed. In case of single map, i set mono channel to alpha as i should, but yes, i've tried other modes just in case and no, that doesn't give me what i need (which is to be expected).

In the attached render, you can see results that i'm getting. #1 is the light without opacity, #2 is setup with 8 bit image in opacity (that is correct result that i want to achieve with single map), #2 and #3 are single map plugged into light material's color and opacity slots, one of them is Max's bitmap and the other one is Corona, both give incorrect result.

I can provide the scene with the files if you'd want to investigate this further, but i'm not sure if i can distribute those hdr files, so we need to arrange the transfer privately.