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banding
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Post by frank // Aug 11, 2006, 5:52pm
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frank
Total Posts: 709
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Any of you guys ever deal with banding when color-correcting / editing images?
Would be neat if there was some type of dithering that could be done at render time to prevent this. ...or a native format beyond standard 24 bit /8 bpc.
One suggestion I found was to use 16 bit-per-channel editing in After Effects but I don't think it does much for an already-8 bit-per-channel image. Also, I've tried the CineMotion Banding Reducer but it doesn't seem to help enough to justify its slow rendering time.
One way to handle it is to add grain before doing any other color/level adjustments...but you typically have to add a lot of grain to visibly reduce banding.
Any other suggestions?
P.S. See attached images... The colors in this case were adjusted a bit overboard so as to better illustrate the banding. |
Post by daybe // Aug 11, 2006, 6:35pm
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daybe
Total Posts: 562
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I can't really think of anything off hand, except apply a blur filter on the areas that have banding or painting over the areas with the brush tool with a low opacity to soften the bands. I do realize this can't be done in every instance, this is a common effect with color correction as it will cause some issues like this when apply lots of color correction, perhaps limiting the amount of correction may help. The grain you use helped but then it seems it limits the corrections made.
What tools are you using to adjust the color?
If I think of anything else I will let you know.
Cheers, |
Post by frank // Aug 11, 2006, 6:40pm
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frank
Total Posts: 709
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Thanks for the tips, Daybe!
You are right about blurring - it does help. Although not done in this sample image, I usually apply some type of process to soften / "warm up" the image a bit. One trick I like is to put the original layer on top (at 80% opacity) of a blurred layer and experiment with the overlay modes. I may do a small blur of the top layer, just to take off some of the sharpness and any possible aliasing on the edges.
For post processing animated sequences, I use After Effects. If it's just a single still, I'd use Photoshop. However, the methods are similar in both apps. |
Post by frank // Aug 11, 2006, 7:04pm
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frank
Total Posts: 709
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I'm going to try a demo of Color Finesse for After Effects. Always heard it mentioned as being a powerful plugin due to its 32-bit floating point color correction.
...but it seems like there has to be another (cheaper) way to get near band-free images.
Hrm... |
Post by frank // Aug 11, 2006, 7:27pm
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frank
Total Posts: 709
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Color Finesse is quite an app. Lots of options.
However, banding is still evident.
Looks like the best method for now is to add grain before doing any CC. |
Post by Anunnaki // Aug 12, 2006, 3:07am
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Anunnaki
Total Posts: 18
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Was your orginal image saved using any compression, such as JPEG?
Vincent D. Brumback |
Post by parva // Aug 12, 2006, 5:29am
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parva
Total Posts: 822
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thats really interesting.
The grainy thing is maybe the same technique other Renderers use.
left MR in Max (Vray Max gives same result) - right LW in tS
2121
I enhanced the contrast and brightness.
Good to see that the MR output is much more noisy.
The other thing is that in real world no surface is really flat
(well a mirror but even that isn't really "flat" and if a surface is flat it becomes very reflective)
so if the surface is mostly rough the light scatters also and the banding effect is less visible. |
Post by rj0 // Aug 12, 2006, 6:21am
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rj0
Total Posts: 167
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The other thing is that in real world no surface is really flat
(well a mirror but even that isn't really "flat" and if a surface is flat it becomes very reflective)
so if the surface is mostly rough the light scatters also and the banding effect is less visible.
Quite right. A fine, subtle bump map map might be about the easiest render-time solution to banding, and that 'is' realistic for most real-world surfaces.
rj |
Post by frank // Aug 12, 2006, 12:11pm
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frank
Total Posts: 709
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Was your orginal image saved using any compression, such as JPEG?
Vincent D. Brumback
Hi Vincent!
I never use JPG or any other lossy formats. Always TGA sequences with RLE.
Sorry I forgot to mention that! |
Post by frank // Aug 12, 2006, 12:16pm
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frank
Total Posts: 709
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The other thing is that in real world no surface is really flat
(well a mirror but even that isn't really "flat" and if a surface is flat it becomes very reflective)
so if the surface is mostly rough the light scatters also and the banding effect is less visible.
Good point there, Parva! That makes sense.
Quite right. A fine, subtle bump map map might be about the easiest render-time solution to banding, and that 'is' realistic for most real-world surfaces.
Nice idea, rj0! I think this would apply also to using texture mapping. Instead of shading with a solid color, create a texture that is the same color, but with subtle noise/variance. In this way you shouldn't have a continuous run of the exact same color, which results in banding.
Hrm...
Good ideas!!! Thanks you guys for the input! |
Post by TomG // Aug 14, 2006, 3:17am
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TomG
Total Posts: 3397
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Another option is to replace a solid color with a simple small image in the texture, and in that image you would introduce some small noise. The noise would be small enough to leave it looking like a single color, but enough to break things up a little in the bands.
This is similar to adding your grain at render time really - which at least keeps the grain on the surface in question, and not over object edges and other places where you might not want it.
Could be faster to render than a bump map too.
HTH!
Tom |
Post by frank // Aug 14, 2006, 3:37am
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frank
Total Posts: 709
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Yep! I think this is what I will try next.
Thanks again to all for the ideas! |
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