On Why the D850 is Revolutionary

Started Aug 12, 2017 | Discussions thread
bobn2 Forum Pro • Posts: 59,151
Re: On Why the D850 is Revolutionary

syberman7 wrote:

bobn2 wrote:

syberman7 wrote:

bobn2 wrote:

Ferguson wrote:

I was hoping for something like 60 megapixels, really push the glass guys, and/or substantially better ISO or DR.

You do a quick calculation, you find that the pixels are the same size as the D500, so ten to a dozen, it shares the same pixel design and most other characteristics.

How do you calculate that? My arithmetic says a D500 sensor in FX size would be 48.4 MP.

D500 DX is 23.5mm x 15.7mm; 5568 px x 3712 px.

D500 sensor scaled to FX is 35.9mm x 24mm => 8506 px x 5686 px which is more than quoted spec of 45.75 MP and actually = 48.4 MP.

That eliminates D500 sensor at equal pixel pitch unless I have something wrong?

Not really. The D500 pixel is 4.22 micron. If we assume that the D850 is 8280x5520 that gives a pitch of 4.33 microns. It's highly likely that within that boundary, the pixel design is exactly the same, there is just a slightly larger spacing on the D850 sensor. Exactly the same happened in the D7000 -> D800. It's unlikely that two completely separate pixel designs were used for each, especially given the way that Sony lays out its pixels.

So are you saying the actual light collecting wells are the same pitch, but they are spaced more widely? Does this mean that the microlens layer compensates by focusing more light in each pixel?

The microlens layer is a separate organic layer sandwiched on top of the silicon. It will have a pitch which matches the actual one used on the sensor, which will focus a tad more light. DR is, however a property of the silicon (and the way it's used, for instance though the D800 and D810 use the same sensor, the D810 gives more DR because Nikon managed to find the capacity to take it down to 64 ISO).

I would counsel against using the term 'light collecting wells', unless you know what a potential well is, and how it is established on a CMOS sensor, it gives an entirely false image of what limits saturation capacity.

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