Rendering with alfa ? - another question, please view again!

[Mathaeus]

If PS means Photoshop, well it's probably the last tool on the planet for checking out this stuff, as it has it's own, fixed method for interpreting the alpha. Method is different for different formats, it's even different by version of Photoshop. From non-existent alpha in targa format in PS7... to whole painfully story about EXR in PS. Actually it's question for Photoshop support...

If you reading 3d renders in 2d apps, you want to checkout:
1: how does it deals with pre - multiplied alpha, or 'straight' alpha
2: how it deals with pre - multiplied alpha in floating point formats (exr and so) - for example, if you have a color over 1, does it clamps this color to 1 before cutting by alpha, or not.

My wild guess is, that Phostoshop likes the straight alpha for PNG fprmat, so maybe you want to disable 'premultiply by alpha" in SI render options.

[pimeto]

Hey man, thanks for reply but i really dont understand what you mean. I can't solve this yet.
Any one else ? Is it a renderer problem, something i need to check in render preferences.