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Banding

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Gregory Bennett
Banding
on Jan 21, 2010 at 8:19:25 pm

Noticed some banding on certain shots that I have color corrected in Color (working from R3D files) and then sending back to conform in FCP using ProRes 422 HQ. The color corrections are not too radical. Looks like blockiness in the image.

Gregory Bennett
Director of Photography
Toronto, ON, Canada
http://www.gregorybennett.com


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Stuart Ferreyra
Re: Banding
on Jan 21, 2010 at 9:40:41 pm

Is the banding on vignettes added to the grade?

Stuart Ferreyra
Timecode Multimedia
Colorist / Post Supervisor
West Los Angeles, CA

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Gregory Bennett
Re: Banding
on Jan 21, 2010 at 9:55:54 pm

Yes. But shouldn't I be able to do vignetting in Color?

you can see trailer here:



The shots in the hallway are particularily noticeable, especially when watching on BluRay.

Gregory Bennett
Director of Photography
Toronto, ON, Canada
http://www.gregorybennett.com


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Colin Hubick
Re: Banding
on Jan 21, 2010 at 10:46:02 pm

Is your Internal Pixel Format set to 8bit in the user prefs?

What kind of monitoring are you doing? just on the computer display or with a broadcast monitor?




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Noah Kadner
Re: Banding
on Jan 22, 2010 at 3:01:20 pm

Yeah 99% of the time I see banding on RED footage it's due to lack of color depth on the viewing monitor, not the actual clip. Remember to correct to a gamma space/color depth that your viewing monitor can display- i.e. REC 709.

Noah

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Graeme Nattress
Re: Banding
on Jan 27, 2010 at 1:48:01 pm

Banding occurs when a smooth gradient at a high bit depth is converted to a lower bit depth and there's not enough natural noise in the image, or no dither has been added during the conversion to smooth out the gradient at the new lower bit depth.

Lossy codecs such as ProRes do a very good job at encoding our images at a lower data rate, but to do that, they must remove from the image what it thinks we won't see. One of the things that gets removed is subtle, low-level noise, which is just the kind of noise that helps naturally dither gradients.

Wavelet based codecs (like REDCODE) behave a little differently because they represent the image as a smooth, underlying mathemetical function, so even when a little noise is lost through the lossy compression, the image is still a smooth gradient underneath, not represented by a grid of macroblocks. This and the quality of the underlying RED image have ensured that I've never seen any banding that actually relates to the underlying RAW data that the camera captured.

So - as Noah points out, banding can often be as the result of an 8bit monitor on 10bit (or higher) data without adequate dithering added.

And, I guess you've all just given me an idea for a Color plugin....

Graeme

- http://www.nattress.com - Film Effects and Standards Conversion for FCP


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Stuart Ferreyra
Re: Banding
on Jan 27, 2010 at 2:34:12 pm

Graeme, in your experience... RED RAW color corrected and rendered out to a 10bit codec such as Uncompressed 10bit and ProRes HQ: Which one will you give a better and smoother gradient?

Sometimes ProRes seems to handle well and other times not so well. Is there a typical scenario when we should not use ProRes? Thanks!

Stuart Ferreyra
Timecode Multimedia
Colorist / Post Supervisor
West Los Angeles, CA

- Visit our studio's website.
- RED Rocket Conversions.
- Follow us on Facebook. Become a fan!
- Duplication, Mastering and Teranex Conversions.


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Graeme Nattress
Re: Banding
on Jan 27, 2010 at 2:49:31 pm

Uncompressed is best as it will preserve the low level dither better. But I find that Color still works best outputting DPX rather than quicktime.

Graeme

- http://www.nattress.com - Film Effects and Standards Conversion for FCP


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Uli Plank
Re: Banding
on Jan 28, 2010 at 1:57:22 pm

Hi Graeme,

you wrote. "And, I guess you've all just given me an idea for a Color plugin...."

Sounds great – if you still find the time.

BTW, I just wrote about your Color plug-ins for the German magazine "Digital Production". They got my recommendation (as you may have expected).

Best regards,

Uli



Director of the Institute of Media Research (IMF) at Braunschweig University of Arts


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Graeme Nattress
Re: Banding
on Jan 28, 2010 at 1:58:43 pm

But I'm not sure you can easily do error diffusion dither on the GPU as it does all pixels at once, rather than sequentially. Email Uli if you have any ideas...

Graeme

- http://www.nattress.com - Film Effects and Standards Conversion for FCP


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