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Thom on Nikon's unanswered questions...

Started Feb 4, 2014 | Discussions thread
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valid points
In reply to jfriend00, Feb 5, 2014

jfriend00 wrote:

Devendra wrote:

I am sure D800/E body is not the limiting factor to flap the mirror (it can already flap at 1/8000 of a second). Expeed 3 may be able to crunch it in 12bit default mode (non-ADL, non-NR etc). I will be happy to pay extra dollars (400-500?) to get this upgrade and maybe a fine tune for another 100. After all photoshop can charge us 120+yr for barely upgrading their software on the average (in cloud). Hope it kicks off. I will be happy, Nikon still makes the bucks to focus on bodies with upgradeable software and impressive feature set. It is a win win across the spectrum of users.

anyway, im just throwing enough ideas and hopefully something will stick its as good of a speculation but variable and dynamic to adjustments rather than sticking with a "born with" set of features. add in replacement sensor, you have a mindboggling set of options and combinations.

The mirror doesn't flap at 1/8000th of a second. The shutter does the 1/8000th and the shutter doesn't even actually open/close that fast. At those speeds, it uses a moving slit across the frame that gives each pixel in the sensor only 1/8000th of a second of exposure, but not all at exactly the same time. The shutter is actually doing exposure for longer than 1/8000th. But, the shutter speed is basically irrelevant here to the fps as long as it isn't really, really slow. The shutter is already way, way, way faster than the fps.

The mirror in the D800 has not been shown to go more than 6fps (in a crop mode). If you remember your high school physics, F=ma which means a = F/m so to accelerate the mirror faster to get it up and down faster to go you need more force or less mass. The mass is probably already as light as it can economically be so generally you need more force. More force means more power from the solenoid that flips the mirror up and then down and more power in the solenoid means more current from the battery. Flipping mirrors faster costs more in parts.

Then, on top of that auto-focus starts to get more complicated when doing lots of fps because the more frames per second you do, the more time the mirror spends up and the less time the AF system gets to see data to do its auto-focus job. It only gets data when the mirror is actually down, settled and not moving. This is often called the "mirror blackout time". A shorter mirror blackout time gets you better auto-focus on a moving subject at max fps. Shortening the mirror blackout time is even harder than just making the mirror go up and down fast enough. It basically means that the mirror has to up and then down even faster so it can be settled and down for a longer period of time between frames.

Now, we know that Nikon can make 8fps mirrors at an economical price because they did it before in the D300 (DX) and the D700 (FX). We don't actually know the max speed that the D800 mirror could go, but I'd say it's unlikely that it's been designed and tested to 8fps when no specification of the current camera requires that.

I'm not holding my breath thinking that it's feasible to make the D800 go 8fps with a firmware upgrade. I think they would need a faster mirror, an EXPEED 4 processing chip and probably some other internal circuitry that could go faster.

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Valid point about shutter vs mirror, but I dont think mirror flipping could be a battery issue. Both D7100 and D800 use the same battery. So 6-7fps is already possible. adding 2more may be a matter of firmware.

I am not crossing my fingers at all. I would rather leave it up to Nikon to come up with options rather than limitations based on my expectations. Hopefully its both ways.

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