Sony a77 appears to fake video specs!

Started Feb 26, 2013 | Discussions thread
TrojMacReady
Senior MemberPosts: 8,429
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Re: I don't think it's line skipping
In reply to Alphoid, Feb 26, 2013

Alphoid wrote:

There are a few standard ways for sensors to downsample from 24MP to 2MP (pixel binning and line skipping are the most common), and many more done in software (but too CPU-intensive for a camera). I believe none would lead to addition blur -- they would just give additional aliasing and moire.

Actually, video softness is widely linked to line skipping (or a combination of line skipping and binning as Canon is suggested to use). Even if the scaling through line skipping itself wouldn't soften the visible output that much, it measurably takes away a ton of resolution and adds boatloads of moire and aliasing. The latter two are best battled with... softening (either through software or a specialized OLPF).

As Sony explains in their high end F65 promotion material (that camera downscales its 4K output from 8K), debayering obviously eats up extra video resolution, in which case sampling from a higher resolution without skipping helps detail and accuracy. That's what you did using a Lanczos filter in Gimp with the still image...

Here and here are two articles that shed some light on it too (even though there are assumptions about the methods used, the theory of sampling explained does make sense).

Apparently most camcorders sample their 1080P signal from a higher resolution (3 to 4 MP) to compensate for the debayering effects.

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