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Perfectionist's Whining: 4K on 12MP


ZZ VISUAL
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2014.04.07.Mirrorless.SonyA7s.1.ScreenVi

 

A "tech geek's" comment inspired by the Sony A7S release... 
 
I appreciate the quality of codec/bitrates of the new Panasonic GH4 (there are several first examples available online), the maturity and all-round versatility of the system, as well as its plethora of great improvements (like the “depth-for-defocus†contrast-detection AF). However, there is one thing on GH4 I have never found to be the most elegant technical solution. Namely, it is rather high megapixel score (16MP).

I do suppose for a motion-stills/video oriented micro 43 camera the optimal resolution would be 12+MP. The arguments are straightforward:

1. 12+MP on a micro 43 sensor is a “native†resolution for the academy DCI 4K standard (4096×2160 pixels). On GH4, DCI 4K is supported in the crop mode (x2 vs x2.3), owing to the higher horizontal resolution of its 16MP sensor (4608 pixels). To note: x2 vs. x2.3 crop is noticeably less pleasant for a video maker (!).

2. Higher continuous shooting rates for stills: 30% speed-up in the continuous shooting does matter (!).

3. Slightly lower ISO noise (and slightly higher dynamic range) in the video and pictures’ modes.

For the motion-stills/video-oriented cameras (1) and (2) is much more important than extra 4 MP in stills. B.t.w, I lived a quite happy stills’ live with my G2 – just be thorough with composition and no need to crop :).

There are well-known successful examples of the strategy (“less MP = more speed/IQâ€) in the DSLR world (Nikon D4 (16MP/FF), Canon 1D (18MP/FF)… And now – “suddenly†appeared at NAB, the first 4K mirrorless full-frame Sony A7S. 

As compared to the GH4, A7S has lower bandwidth/processing power (50 Mbps vs. 200 Mpbs for 1K, UHD (3840×2160) vs. DCI resolution, 4:2:2/8 bits vs. 4:2:2/10 bits etc.) with the advantage in the high ISO of course. Note that A7s has also 14 bit RAW for stills. However I would rather applaud Sony for limiting the sensor resolution by 12MP. It is a very harmonic engineering solution for the motion-oriented hybrid camera.

Dreaming forward about 4K on micro 43… I would like to see two lines of Panasonic sensors: 16MP for the stills-oriented cameras and 12MP for the motion-oriented ones. For that I would gladly pay extra. Apparently, Panasonic thought about it more than me. Sadly, they do not follow this path likely due to the high financial burden for maintaining the two lines of the "perfect" sensors on one consumer’s products line. This is in contrast to Sony which always seem to have enough cash to sit on several sits (e.g. A7, A7R, A7S, NEX, ... )…

PS I do not intend to compare 4K/micro 43 vs. 4K/mirrorless-FF as systems themselves here: the pro/cons are be basically the same as for the stills’ counterparts.

Stay tuned,
ZZ VISUAL

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Panasonic cameras use a pixel averaging system to dump data for video where Canon use line skipping to achieve the same thing.

Panasoinic Cameras are very very good at pixel averaging that is why the images from their cameras are so good and have so little moire compared to other cameras - so Im not really that concerned that the GH4 is a 16mp sensor.

, and mega hi iso does not really appeal to me , I rarely ever shoot over 400 iso

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Panasonic cameras use a pixel averaging system to dump data for video where Canon use line skipping to achieve the same thing.

Panasoinic Cameras are very very good at pixel averaging that is why the images from their cameras are so good and have so little moire compared to other cameras - so Im not really that concerned that the GH4 is a 16mp sensor.

, and mega hi iso does not really appeal to me , I rarely ever shoot over 400 iso

 

We do not speak about bining to 1K here (there is no bining in the 4K mode on GH4) - otherwise there would be no x2.3 crop (instead of the native x2.0).  

 

The ISO advantage  between the 16MP and 12MP sensor pixel densities is rather small (~1/3 step) - that is not ISO what makes 16MP less fit for 4K than 12+MP (see item 1 in the post). But for the continuous shooting reduction 30% in the file size does matter (item 2). 

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