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>Is there anything I can do?
Not much. You could lower the ranges by adjusting the levels and saturation, but beyond that: nada. Both red and green share the same color component and thus compression literally suffers from starvation. There is simply not enough fidelity in it to get both of them over halfway decent. There will always be artifacts, even after adjusting stuff.
?> Is there anything I can do?
Not really. You are dealing with an artifact known as chroma bleed caused by extreme jumps in pixel color data between adjacent elements, also known as pixel risetime.
Your only hope is to accept it or play with it. You can add a bit of blur that will hide it by forcing a new compression artifact at the transition between the offending pixels.
Thank you all for your replies.
Reducing saturation on everything seemed such a drastic solution and things ended up looking very murky. So I completely revised the style of the animation instead and added white strokes around the offending colours which meant that the colours were restored and no bleeding. Sure the style slightly changed but I think it's better for it!
I am interested in reading up on CHROMA BLEEDING for future reference... Any suggestions on where to research the subject?
Also, is there any rule to avoid this kind of effect? Does this occur when certain combination of colours are chosen?
>Also, is there any rule to avoid this kind of effect? Does this occur
>when certain combination of colours are chosen?
No and no. The weakness is in the compression and chroma sub-sampling, not the colors. You can even get this behavior with your white borders. For starters, take a look at the include Color Finesse plugin and check its graphs. When you play around with the respective curves, you will see how colors are translated from RGB space to YUV space. Then check out sites like Wikipedia, ITU, IBE, the MPEG authorities or anything related to broadcast specs. You should find some site that explains the YUV/YIC/Ycbr encoding scheme and the 4:1:1/4:2:0 chroma sub-sampling.
The best way to avoid the problems inherit in chroma sub-sampling is to avoid codecs that sub-sample, especially DV. Obviously that's not always possible, but be sure to avoid going near DV until the very last stage of the production pipeline (use lossless codecs wherever possible), and make certain you never double-encode any footage.
Thank you very much to you all.
You've been very helpful and educational!