Another issue from the above posts:
- you render something in Corona against some background
- you want to replace the background or move the object into some other place of the image
- you render a mask of this object, save in 32-bit exr with alpha channel, no post processing, and do other fancy stuff to make sure all is fine
- in the end... OMG BORDERS!
Why?
Because Photoshop is unable to interpret the alpha channel correctly!
Use Fusion (it's free) or other software that is made specifically for compositing. It will handle just fine whatever complex alpha-channel-masked-32-bit-exr you throw at it.
If you are having issues with this - again, please send us sample files (max, exr, other) and let us know how to reproduce your issue. We will look into it.