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Banding in 16bit, but not in 8 bit

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Martin Stacey
Banding in 16bit, but not in 8 bit
on Mar 6, 2019 at 6:07:22 pm
Last Edited By Martin Stacey on Mar 6, 2019 at 6:08:40 pm

Hi,

Was wondering if someone can help me out, as this is confusing me.

I'm seeing banding in the After Effects viewer in 16 bit on gradients. In actual fact, it looks very similar to the same gradient at 8 bit.

But, if I render that same gradient as a Prores 4444 set to millions of colours and bring it back in the banding is gone, and looks great. Even if I then change the project to 8 bit, it looks better than at 16 bit.

And also if I render it as Prores 4444 set to trillions (which should in theory have less banding) it has the same banding as the AE viewer.

I understand that AE does an internal dithering at 16bit, but I think maybe something broke in one of the CC updates, cause it looks like 2019 isn't doing this internal dithering unless you render in millions of colours.

Surely an 8bit render shouldn't look better than a 16bit?

I've attached a scene file if anyone wanted a play. (viewing individual channels helps show the issue)
13182_bandingissue.zip

Cheers


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Walter Soyka
Re: Banding in 16bit, but not in 8 bit
on Mar 6, 2019 at 6:24:18 pm

[Martin Stacey] "I understand that AE does an internal dithering at 16bit, but I think maybe something broke in one of the CC updates, cause it looks like 2019 isn't doing this internal dithering unless you render in millions of colours. "

Ae only dithers when stepping down from a higher bit depth to a lower one. In other words, it's not switching to 16bpc that activates dithering; after all, that would mean that Ae was arbitrarily degrading your image even though you had selected a higher bit depth!

It's asking Ae to step a 16bpc image down to 8bpc that activates any dithering, which is precisely what happens when your project is set to 16bpc and you render to Millions of Colors.

Remember that some of the banding you are seeing at 16bpc/Trillions may be caused by your monitor, rather than the actual image itself.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Martin Stacey
Re: Banding in 16bit, but not in 8 bit
on Mar 6, 2019 at 6:55:06 pm

Ah ok, I get ya.
It just seems weird that to get the best looking gradients you need to render at a lower bit depth. And that also once that file is rendered you can switch to 8bit and this rendered gradient looks much better than when working in 16bit.
If only AE made the dithering function available as a filter it'd solve a lot of banding issues.


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Kalleheikki Kannisto
Re: Banding in 16bit, but not in 8 bit
on Mar 6, 2019 at 6:33:26 pm

I'm by no means an expert on the matter, but my suspicion is that it has to do with the bit-depth of the file format as well as the monitor.

ProRes 4444 supports up to 12 bits per channel, so storing 8 bits per channel without losing information would not be a problem but 16 bits would.

Similarly, most monitors show 8 bits per channel which poses no problem to display an 8-bit image as intended, but a 16-bit image -- or a 16-bit image converted to 12-bit for storage and then converted to 8-bit for display -- has some definite possibilities of losing some accuracy along the way.

But that's an educated guess at best.

Kalleheikki Kannisto
Senior Graphic Designer


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Martin Stacey
Re: Banding in 16bit, but not in 8 bit
on Mar 6, 2019 at 7:02:10 pm

Yeah, it's more the idea that rendering at a lower bit depth looks way better that I found puzzling.
Also I think I would have noticed this in previous versions if AE if it had been doing it then.


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Chris Wright
Re: Banding in 16bit, but not in 8 bit
on Mar 7, 2019 at 6:30:10 am

i would try another codec just to be sure as there have been many software glitches with output codecs that shouldn't be there. and one of them was prores, at least a while ago on the adobe.com forums.


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Martin Stacey
Re: Banding in 16bit, but not in 8 bit
on Mar 7, 2019 at 3:46:44 pm

Yeah, it's not that I think anything is wrong with the codec,
It's that it seems strange to me, that the best way to get rid of banding is to work in 16 bit, but to render to millions of colours, as opposed to trillions.

So this is the AE Viewer in a 16 bit project:


This is a trillions of colours render which looks the same, which makes sense:


And this is the same project in 16 bit, but rendered to millions of colours:


which in my opinion is way preferable to the AE Viewer or the trillions render because AE is dithering so the banding is much less obvious.
So it seems the way to get the best looking final delivery render would be to work in 16 bit, but to render to 8 bit depth, not 16 bit.

Which seems odd.


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Walter Soyka
Re: Banding in 16bit, but not in 8 bit
on Mar 7, 2019 at 3:56:21 pm

[Martin Stacey] "If only AE made the dithering function available as a filter it'd solve a lot of banding issues."

[Martin Stacey] "So it seems the way to get the best looking final delivery render would be to work in 16 bit, but to render to 8 bit depth, not 16 bit. Which seems odd."

Remember that some of that banding is likely caused by your monitor.

Dithering is not really a filter or effect; it's an interpolation method. If you want to get the effect in a 16bpc without rendering, you can add an 8bpc effect to force that interpolation. For example, an adjustment layer with an Arithmetic effect applied (the defaults will not affect the image, other than forcing it down to 8bpc) will get you that dithered downsampling.

Note that this will cost you precision; Ae will resample the resulting image back up to 16bpc, but the original 16bpc precision will be lost in this process.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Martin Stacey
Re: Banding in 16bit, but not in 8 bit
on Mar 7, 2019 at 4:12:23 pm
Last Edited By Martin Stacey on Mar 7, 2019 at 4:32:36 pm

Yeah, I'm on a 10bit Imac retina, and I get that some of the banding will be caused by the screen.

I tried that with the arithmetic plugin, and although it did a more pleasing dithering it also introduced banding that wasn't there in the "16 bit millions" render.

with arithmetic plugin:


16 bit project rendered to millions:


Sorry to go on about this, I'm not being awkward, but I just want to make sure something isn't going wrong here. Banding in grads is something I'm really trying to avoid, so I'm looking for the best solution to get rid of them, and it's led me to point.
A lot of the time I'm going to a deliver codec like HAP, which is really bad with banding, but it seems much better if I render a 16 bit project down to prores 4444 millions of colours, 'cause it introduces the dithering, which then reduces the banding in the final HAP render too.


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Walter Soyka
Re: Banding in 16bit, but not in 8 bit
on Mar 8, 2019 at 10:55:58 am

[Martin Stacey] " Banding in grads is something I'm really trying to avoid, so I'm looking for the best solution to get rid of them, and it's led me to point. A lot of the time I'm going to a deliver codec like HAP, which is really bad with banding, but it seems much better if I render a 16 bit project down to prores 4444 millions of colours, 'cause it introduces the dithering, which then reduces the banding in the final HAP render too."

Yeah, Hap is pretty notorious for banding, and you fill be fighting this fact for the entire project. You can always introduce a little bit of noise across the whole frame, or try a more nuanced tool like S_Deband from Boris FX / Genarts Sapphire.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Martin Stacey
Re: Banding in 16bit, but not in 8 bit
on Mar 11, 2019 at 2:32:18 pm

Yeah I've found that for HAP just a 5% noise over the top creates the least banding. 16bit reduces it a little further, but doubles the render time, so you've got to take that into consideration.


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