Yikes! The rumored Nikon D800.

Started Oct 5, 2011 | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 60,519
Part 2

orpheo wrote:
Thanks for your answer.

bobn2 wrote:

We can accurately predict the performance of the three sensors from the measurements DxO has made of the pixels.
D700 pixel has 38% quantum efficiency and 5.3 e- read noise
D3s pixel has 57% quantum efficiency and 2.8 e- read noise
D7000 pixel has 48% quantum efficiency and 2.5 e- read noise (4.3 e- at 12MP FX)
So for the same exposure, the photoelectrons collected compared to D3s, will be

D7000 FX 0.84x, giving a highlight/mid-tone noise of 1.1x, basically 0.25 stop worse.

D700 0.66x, giving a highlight/mid tone noise of 1.25x, basically 0.6 stop worse
In the shadows, again based on the D3s we'd get

D7000 FX, noise is 1.54x, D700 noise is 1.9x. One way of looking at the combined effects is 'tonal range', as defined by DxO. In this case we get, at 25k ISO
D3s - 5.5 bits
D7000 FX - 5.1 bits
D700 - 5.09 bits
Thus this will be a little better than the D700, a bit behind the D3s.
This is based on measurements and analysis.

I can't quite follow all of your math
(by the way, where do you find that data?)

http://www.sensorgen.info , I don't find it, I produce it from DxO data.

but I'd translate it to that: enlarge the D7000s-Sensor to FF and you end up with about 37MP while pixelsize stays the same. The low-light-perf will rise according to the larger total light collecting area and the result will still be better than with the 3x bigger pixels of the much older D700. Is that correct?

Yes

The pure pixelsize-is-all-theory would propably say it stays the same and only rises a little when the image is downsized.

It will be wrong, then. Read here http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/

My guess is, it will be somewhere in between.
So my question is, where is the tipping point?

somewhere very small, a long way below what we've seen yet.

Or back to Nikon 1: that would result in a 74MP FF-Sensor with the same DxO-sports-score as the D3s?

Yes

And they only don't build that yet because of speed-considerations or production-cost or something like that?

We don't know what they'll put in the D4 yet. The processor in the 1 series will do 24MP at 24FPS, that might just be what Nikon does, it would be very interesting.

But then surely there would exist some high-tech-camera maybe for astronomy-uses that already has such a sensor - do you know of any example?

Actually, it is unlikely. The consumer CMOS sensors are a different design branch to the CCD's typically used in science, and science doesn't have the investment to produce something similar.

At the end of the day, I'm interested in understanding technical aspects to a certain degree and that is why I read and discuss in threads like this from time to time.

But as a consumer I just want a camera to fit my Canon-lenses, which at least equals the low-light-perf of a Nikon D700 (but "usable" up to 25k).

The 5DII is pretty close, what does for it is the pattern noise.

I would actually prefer, if it could be done with less than 36MP, so I don't have to buy a new computer yet Other than that I really don't care how much MP it has, as long as it doesn't go below 12. (Of course there is some other criteria like pricerange, size+weight, AF and so on.)

So perhaps my conclusion, Canon could do it if only they wouldn't squeze so many pixels on their sensors, is not scientifically correct. But I'm afraid it might be true in the reality of the cameras to come next.

I think Canon won't change how they go about things. Nikon seems to, when they see an advantage.
--
Bob

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