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DSLR artifacts


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#1 Tim Schroeder

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Posted 12 November 2014 - 08:25 PM

Having been shooting on DSLR's for awhile (t4i) I thought I had gotten the hang of things.....but now in the color correction process I seem to be encountering some odd digital artifacts (seen below).

 

Is this just anti aliasing or am I over correcting the footage?

 

 


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#2 David Mullen ASC

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Posted 12 November 2014 - 08:26 PM

There is no link attached. ("Aliasing" would be an artifact, "anti-aliasing" would be a technique to get rid of the artifact...)


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#3 Adrian Sierkowski

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Posted 12 November 2014 - 08:26 PM

There isn't anything embedded; but vDSLRS really don't hold up well to any post pushing around owning to their rather crap encoding codecs.


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#4 Tim Schroeder

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Posted 12 November 2014 - 08:31 PM

64270_558510264279173_356444085877522863


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#5 David Mullen ASC

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Posted 12 November 2014 - 08:47 PM

I assume that's noise all over the trailer and not textured snow & ice?  And there is no noise in the original footage, only after you color-corrected it?  Did you have to make the footage lighter?

 

Or are you talking about the aliasing / moire along the horizontal lines of the trailer?


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#6 Tim Schroeder

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Posted 12 November 2014 - 08:55 PM

I'm talking more about the aliasing/ moire.

 

That's actually not noise though, it's just a film grain effect I used to try and mask the noise already present, which actually was almost non-existent upon further inspection.


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#7 David Mullen ASC

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Posted 12 November 2014 - 10:03 PM

The moire is inherent to DSLR's because their anti-aliasing filter is designed for the full sensor when using all of the photosites for stills, not HD video where they have to get 18, 24, whatever megapixels down to 2 megapixels before raw conversion to RGB through line skipping and pixel binning.
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#8 Tim Schroeder

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Posted 12 November 2014 - 11:44 PM

Any ideas on how prevent or fix this problem? 


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#9 David Mullen ASC

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Posted 13 November 2014 - 02:32 AM

http://philipbloom.n.../09/13/moire-2/

http://www.mosaiceng...ts/vaf/faq.html

 

You'll probably see some softening though.

 

Or you can try a DSLR that records 4K video like the Sony A7S and Panasonic GH4; because they don't have to pixel bin to get down to 2MP HD, their regular anti-aliasing filter works well in 4K video mode.

 

Or don't shoot video on a DSLR, use a video camera.


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#10 Keith Walters

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Posted 13 November 2014 - 08:37 PM


 

Or don't shoot video on a DSLR, use a video camera.

What he said :rolleyes:

From Day #1 just about all digital cameras have given users a live video recording facility of one sort or another, basically because it requires little more than a few more software algotithms, which cost little or nothing.

 

After all, the first digital cameras were little more than domestic video cameras set up to capture individual video frames onto flash memory instead of tape. Although they've evolved enormously since then, the same basic principles still apply, except that capturing tull stills-resolution images at a normal video frame rate is still somewhat beyond the capabilities of consumer-grade battery-powered signal processing. So consequently only a small subset of the pixels is actually used, and so the optical low-pass filter is not optimized for video resolution, and so you get aliasing.

 

I know the new iPhones are supposed to be able to capture 4K video, but I have a hard time accepting that the microscopic lenses they use could usefully focus that resolution.

 

Nonetheless, several years ago I made a joking comment here to the effect that "by 2015" stills cameras with 4K video capability would be appearing in Aldi's "Suprise Buys" aisle. Damned if that doesn't look like it might be actually happening!


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