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Banding on colour gradients
Hi guys,
I have produced several animations with subtle background gradients that produce a lot of banding when rendered (rendered to Blackmagic 10 bit codec) even when I add a large amount of fast blur.
My questions are, how is this banding created and how can I prevent it?
Many thanks.
Marc
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6 Replies
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At first guess it would be a bit depth problem… but im no expert
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As far as why, I’m no expert either. But I think Jason is correct.
As far as how to get rid of it, add some noise and then blur the resul. Back in ancient pre-historical times on the WWUG, there was a recipe which I can’t remember. I think I usually start with about 4% monochromatic noise and .3 px gaussian blur, and then just fiddle with it until it looks OK on a video monitor.
Also, I usually do it in Photoshop and then re-import the layer. My thinking is that this saves AE from having to constantly redo all that pixel crunching.
YMMV (Your Mileage May Vary)
Greg
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Therz a nice plugin from tinder box called t-band, its in one of there collections
chk them out
regards
Hemanth -
It is a bit depth problem…. I’m no mathmetician but will try to explain.
8 bit is a mathematical calculation of the amount of variations that can happen when 1 and 0s are changed in a 8 number (bit). The result for 8 bit gives 255. Three channels of 255, RGB. Multiple these three channels together (255 x 255 x 255) and this gives you the possible amounts of colours
(16 581 375)…This ring a bell ??? ever heard of 16 million colours (add the alpha and you are at 16 million +).Now ten bit is a number that is ten digits long of ones are zeros. Of course the amount of possibilities is greater….it is greater still with 16 bit (trillions of colours).
When you see banding, what you are in fact seeing is the computer trying to draw the resulting value, but unfortunately the values it is trying to draw fall outside of the millions of colours, so instead of being able to draw nice and smooth, the computer has to put the nearest available colour….this results in two or more colours having the same value giving the appearance of banding.
Now, what can you do to get around this ??? Try to work in the highest possible color depth possible. Try to have less variants in your gradients….try to blur out the banding…..pretend you don’t see it until your boss does.
Hope this helps
Mark
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Usually setting your project bit-depth to 16-bit will help (if the gradients are created in AE that is…). Even when rendering to 10 or 8 bits in the end, AE adds a little dither to avoid banding.
The alternative is to add a tiny bit of monochromatic noise to layers that cause banding.
Bar3nd
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Sometimes your image is actually fine, but it’s your graphics card drivers that mucks it up by doing a lousy gamma correction or Colorsync recalibration of your screen…
Are you seeing the banding on a final non-compressed output to a TV-monitor ?Especially if you’re viewing it on a calibrated Computer monitor or through a firewire camera, or after burning it on a DVD, chances are the initial image wasn’t that bad, but the problem got introduced somewhere between getting the actual RGB values onto the screen you’re watching.
When I color-calibrate my 4 years old Apple Cinema Display, I can see banding on a simple greyscale ramp in 32 bit.
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