D600 95% Video Image Area Solved.

Started Dec 26, 2012 | Discussions thread
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Peter iNova
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D600 95% Video Image Area Solved.
Dec 26, 2012

DPRs review of the D600 includes this:

"The D600 outputs 1920 x 1080 video via its HDMI port, but for no logical reason that we can work out, the actual image area is smaller than those dimensions by about 5%, and the difference is made up with a black border around all four sides of the video image area."

The output image is the full HD frame, but the amount of surface area of the image chip involved in video frame image making is only about 95% of its width. Here's the exact number: 95.7446...% meaning that the 16:9 image is created from 5760 x 3240 of the original 6016 x 4016 used for stills.

The state of the art today in HDSLR cameras has a fair ways to grow before all problems are flattened.

One of the compromises right now is that video images are lifted off the image chip using a variation on the math jumbling that was used to deliver live views off the first digital cameras. Meaning, don't try to read every photosite on the chip—that's too much data!

So in video mode only a fraction of the horizontal photosite rows is read out for its data, then an odd number of them are skipped before the next one is read.

Why odd? if the first row polled is GBGBGB..., then the next one must be RGRGRG... so the two of them can be combined into a Bayer Array with all colors represented in each 2 x 2 chunk.

As it turns out, by only polling this inner 95.7... % of the available photosites, the 1080p math has the D600 lifting exactly 1 in every 3 horizontal rows of data to make the large HD frame. It probably pulls a few more so the top and bottom rows aren't compromised.

Any visual data that falls on the two rows of photosites between the ones that are used suffer a bad fate. All the processing in the world won't bring them back. Moiré, aliasing and false color fringing will come from them.

Future cameras will read every single image photosite to make the video frames. Meaning they will be able to capture 4K, 5K, even 8K moving images with near zero digital artifacts.

-iNova

NB: I couldn't find another thread with this info, so this is an adaptation of the ideas about image construction from my upcoming iBook on the D800, which shares a similar math conundrum.

Nikon D600 Nikon D800
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