Why does Pentax FF have to truly be FF?

Started May 25, 2012 | Discussions thread
stephenmelvin Veteran Member • Posts: 4,547
About that D800 Video...

Joseph S Wisniewski wrote:

Why would Sony release a 24 MP camera when there is Nikon D800 with 36 MP? I guess they (in their mind) will hope to sell it on other specs (12 fps, 100 AF points, and video specs

Like I said earlier, 30-40mp is the "S=sweet spot" for video, 3.5x decimation, the first decimation factor that makes sense for 1080p. 30mp for a full frame width, 36 for Nikon's slight crop. If I were Sony, I'd go 30mp.

But the D800 line skips, like the 5D Mk II. That's why it falls completely apart at ISO's where the 5D Mk III is hitting its stride.

Look at the complaints about Nikon D4 and Canon 5D III video softness compared to D800, and you'll get an idea of what getting the scaling factor wrong does to you.

I don't think the D800 is scaling the way you describe at all. Here's an analysis from Falk Lumo:
The D800 creates FX 1080p video in the following way:

1. Crop a region of 6720 x 3780 sensels (crop factor 1.095).

2. Read only every third line out of this region, but all sensels in a line. The result is an 6720 x 1260 sensel RGGB Bayer pattern which can be demosaiced.

3. The resulting 2240 x 1260 RGB image is downsampled 7:6 to the final 1920 x 1080 px resolution.

4. Compared to an optimum architecture, only 1/3.6 of sensels are read which makes the D800 lose up to 1.8 stops in high ISO video performance.

5. When zooming into a live view image, the D800 switches line skipping from 3x to 2x.


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