DSLR Video - how does it work? (techincal)

Started Oct 20, 2009 | Discussions thread
DSPographer Senior Member • Posts: 2,479
Re: DSLR Video - how does it work? (techincal)

This is a good question which can be answered by carefully examining test images. The subsampling method changes the appearance of aliased details so an image of a zone plate is a good place to start:
http://reduser.net/forum/showthread.php?t=22517

This shows the 5D2 has huge aliasing in the vertical direction (consistent with row skipping) and less but still significant aliasing in the horizontal direction (consistent with binning). Using this result along with the quality of the high ISO video and knowing that the video image exactly fills the same horizontal width as a still image leads me to suspect the 5D2 does the following:

Bins together 3 consecutive same color pixels horizontally and skips 2 of every three rows vertically to generate an 1872 by 1053 (after cropping to 16x9) Bayer pattern image. After de-mosaicing to an 1872 x 1053 RGB the video encoder scales to 1920 x 1080 then encodes to MPEG-4.

Since the Nikon high ISO video isn't better than the Canon cameras and the Nikon's also have weird looking diagonal line features I think they also must do some sort of pixel skipping. I think pixel skipping has always been standard for live view and video implementations for D-SLR and point and shoot digicams.

 DSPographer's gear list:DSPographer's gear list
Canon EOS 5D Mark II Canon EOS M5 Canon EF 24mm f/2.8 Canon EF 50mm F1.8 II Canon EF 200mm f/2.8L II USM +4 more
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