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rich

Straight Alpha problem

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Though i had premultiplication in AE figured out until today. So i've rendered a sequence with a straight alpha as i want to composite it over a background in AE. If i put my normal yellow bg behind it in After effects then i get a small white halo. However if i darken the yellow or make the solid black, it goes away. Have interpreted the render as straight alpha and theres nothing more complex than that. It seems as tho the lighter i make the background the more apparent the halo is. I've rendered the image out of cinema 4D on best antialiasing settings and the image is rendered at full size. The whole point of straight alphas is so that theres no fringing, so where could this white halo be coming from?

 

Anyone know why this might be happening?

 

Thanks very much

 

 

Render with straight alpha

http://www.flickr.co...in/photostream/

 

On yellow lighter background (white halo)

http://www.flickr.co...in/photostream/

 

on dark grey

http://www.flickr.co...in/photostream/

Edited by rich

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you using cs5? i have a bad feeling that it might be cs5, coz on a recent project the compositor also had problems like this. And this was the first time i've heard of them. Ussually i output straight alpha's and no issues. maybe AE cs5 stuffed something up?

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Correct me if I'm wrong, because I don't have C4D in front of me right now to check this, but I seem to remember that whenever I have had to render from C4D to alpha, I had to choose the opposite type of alpha from what I wanted. If I wanted a straight alpha in AE, I had to render it out as premultiplied in C4D for AE to interpret it correctly as a straight alpha. It sounds stupid, but it worked as far as I remember.

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