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29th May 2009, 04:01 | #1 | Link |
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What is the deal of grain retention
I should have asked this question a long time ago. Lurking around the forum, and I often hear goals of retaining grain.
Why in the world would you want to retain grain?!? I thought grain was an unwanted artifact from video cameras. Why would you want that? In real life the world isn't filled with grain, so it is not for realism. For me MVDegrain 3 is one of the best feature of encoding. If it is an artifact, and it is not for realism, why would you want to waste huge amount bits on grain?? |
29th May 2009, 05:06 | #2 | Link |
Fighting spam with a fish
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Grain is also an "Ambiance" factor. A mark of "classic" film is that of natural film grain. Film grain has been in movies for ever, and some (lots actually) like the affect that it provides. Reminds them of old times or something. In addition it prevents banding by providing dither, and gives the illusion of detail as well.
I filter my film grain heavily, but just so that there is only a sprinkling left. I don't eliminate it entirely. But that's me. |
29th May 2009, 06:06 | #4 | Link | |
Derek Prestegard IRL
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Quote:
If we're talking about CCD / CMOS sensor noise (aka "grain") then yes, this is highly objectionable and can be removed in many cases - particularly chroma noise. That ugly blue and red noise you see on high ISO digital camera images is what I'm referencing here Grain is a part of all true film. Sometimes I find it best to just keep as-is, and sometimes I filter it. Very rarely do I try to remove "all" grain, because this usually results in an ugly, over-filtered image. It also often creates banding in the unfortunate 8 bit YV12 color-space we get to work with In fact, in most cases I add artificial grain after processing images for this very reason. Still, to each his own. MDegrain/2/3 are all amazing filters, and there's some seriously good hardware out there in the pro sector as well. ~MiSfit
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29th May 2009, 17:02 | #5 | Link |
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I personally like the look of grain myself, but too much is still too much, though. And even if I didn't like it, I'd still prefer it over (over)smooth video with ugly banding.
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29th May 2009, 18:40 | #6 | Link |
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Digital cameras like RED is way to go, hope they will trash their old cassete cameras soon.
And I hate when they digitally add grain, unless it is needed for effects like in "300" movie. They can add "grain" or "black & white" features to disc players, for customers who need it. Last edited by zn; 29th May 2009 at 18:42. |
30th May 2009, 07:56 | #9 | Link | ||
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Quote:
Quote:
Digital cameras have "grain" too, often to a far larger extent then large format low grain film. |
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30th May 2009, 20:12 | #11 | Link |
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In practice, it is spatially correlated by the complex debayer filters (all high resolution digital cameras use bayer AFAIK). Also, theoretically, the fact that the ccd is partitioned into squares and not points will introduce frequency correlation aswell. Also, film grain should have a simple gaussian correlation, which is not exactly difficult to deal with. Furthermore, none of the denoising methods I would consider actually using would be significantly negatively affected by a simple positive spatial correlation.
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30th May 2009, 22:52 | #12 | Link |
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The sample footprint is determined more by the anti-aliasing filter than the sensor shape.
There is nothing simple about spatial correlation, it's the only real distuingishing feature of signal compared to noise you have to work with in spatial denoising ... the only methods which wouldn't be negatively affected are purely temporal. |
30th May 2009, 23:31 | #13 | Link |
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I think the primary reason why we need "grain retention" is because of this: If a decoder cannot retain the grain in a movie, then the result will not be a perfectly degrained video, but an ugly blurred mess! So if you want a good quality encode, you must either use high quality pre-processing that removes most of the grain without generating additional artifacts (e.g. MVDegrain) before encoding -or- you must use an encoder that retains the grain in a decent way. But high quality pre-processing is slow, really slow. Plus there are far too many thing that can go wrong with bad noise reduction, as seen in many releases! And as mentioned before, not everybody likes degrained video. The grain gives the film a "natural" and more detailed look. Strong denoising creates an "artificial" look. That's why I'm usually not a big fan of denoising...
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31st May 2009, 02:11 | #15 | Link | |
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IMO quite often you see faces that have been degrained much too strong and thus look unnatural. More like dolls than humans (That maybe doesn't happen with a good degrain tool, such as the one from MVTools)
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31st May 2009, 02:17 | #16 | Link |
Mr. Sandman
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complete nonsense. grain exists since the first life form with a visual system called "eye" appeared on earth.
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31st May 2009, 11:59 | #18 | Link |
brainless
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And since there is grain being produced by the eye our neural network called 'brain' is able to filter it out temporally if you stare for long enough on a object
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31st May 2009, 13:58 | #19 | Link |
Mr. Sandman
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*** BUT ***
guess what? videos are not a stable objects (images)...
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