Is there time for an interchangeable sensor DSLR?

Started Oct 19, 2012 | Discussions thread
Joseph S Wisniewski Forum Pro • Posts: 34,136
Excellent points. You missed a couple...

kb2zuz wrote:

I listed MFDB's because I'm very familiar with them, but I also mentioned the Ricoh which is on the opposite end of the spectrum. The sensor and the processor are tied at the hip. The processor needs to know the CFA arrangement, the spectral response and the curve of the sensor, the spectral transmission of the CFA, IR, and AA filters, the bit depth of the A2D (which has to be on the sensor for speed), the noise charactersistics, the characteristics of any microlens array...

Yes, it needs to know all those things. There's also the matter of the interface to the sensor. The D3/D700 sensor that the OP keeps going on and on about is an analog interface, the sensor outputs a bunch of varying voltages, on parallel lines, and a bunch of A/D converters have to surround the sensor and convert those voltages to digital data. To do what it does, the D3 actually needs 6 converters, each converter is 2 channels, so the sensor board is huge, almost as big as the whole camera back. You can't get that board out through a small slot, and it's the D700 sensor that the OP keeps going on and on about.

D3X and D800 use sensors with onboard A/D converters, so there's surprisingly little stuff around the sensor, except for sophisticated voltage regulation that lets those onboard A/D converters operate cleanly. The fact that Nikon added so much great power control to the D3X sensor board explains why it has two full stops better high ISO and shadow detail performance than Sony A900, which used exactly the same sensor, but doesn't do as well with the power.

D2X used converters on a separate board.

Past the A/D converters, you have different processor requirements. The D3's 6 converters produce 6 digital channels, the D3X's digital sensor has two fairly high speed digital interfaces.

I use those examples because they were from the same generation, and they show that you can't just unplug a 2 channel digital interface sensor (D3X) and plug in a 12 channel analog interface sensor (D3). You obviously have to change other stuff. There's a preprocesor on D3 that combines the 12 channels into 2, which D3X obviously doesn't need.

The firmware on the processors is specific to all of these factors and more. Now it appears that you think that the sensor could just tell the processor and the processor could act accordingly, but the reality is that the firmware doesn't just have this raw information, very complex calculations have been run on these to create specific tone reproduction curves, color reproduction algorithms, noise reduction algorithms, etc... the processor can't just do these on the fly. So yes the firmware would have to be updated to support new sensors.

The issue being locked into proprietary systems is that there will not be a large market, and a sensor is only worth making if millions and millions can be sold,

Exactly! I've pointed that out, too.

or they can be sold for very high prices (which is why MFD costs so much).

it doesn't help that MFD sensors are made by aerospace suppliers...

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Rahon Klavanian 1912-2008. Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed. Ciao! Joseph

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