http://vimeo.com/11099771
I am not saying that one is better over the other, I know there are those who will swear by straight Alpha channels and some who will stand behind premultiplied Alpha Channels. I prefer Premultiplied Alpha channels as I feel it is more a more robust and durable alpha format.
Straight Alpha channels on the other hand always give me halos and serious pixel issues. If someone can give a good argument as to why Straight Alphas should always be the alpha of choice, then I will abide.
This was a little issue that came up while working on the “confetti” for my sports project. I was a little sick so don’t mind my congestion, I should be better soon. Enjoy!
This is an example of a straight alpha channel. A. Separated color channels B. Alpha Channels where the black defines the transparency and C. The composite of the separated color channels and the transparency channel to show the blue background. (courtesy of Adobe Help.)
A premultiplied alpha channel does not create B (a separate transparency channel) but stores the transparency information within A (the color channels).