Is there time for an interchangeable sensor DSLR?

Started Oct 19, 2012 | Discussions thread
kb2zuz Veteran Member • Posts: 3,202
It's here

Theodoros Fotometria wrote:

According to the now 3 years old Nikon patent, the sensor will be at the edge of a small box (much like the screen of a small cell-phone), which will be slotted in position from the left side (as we look at the VF eye-piece) and it will be user interchangeable....


They already exist. Medium format digital cameras are often this way with a removable back. There are several problems that come along with it:

First is the reality that the sensor alone is not enough, the processing software and many times the processing chip is designed to work in concert with the sensor. The processor would have to know how to deal with demosaicing a color file and the layout of the sensor filters, if you put in a B&W sensor, it would have to know that it's a B&W sensor and how to deal with a B&W image instead of a mosaic color file... noise reduction algorithms and settings all have to be changed on each sensor. As a result you probably want to build the processor onto the sensor unit. Now you'd still need a secondary processor on the body to run the LCD, card reader, exposure unit, autofocus system, etc. Do you plan on all of these would be full frame or DX? Because if you plan on both, then the viewfinder and AF units would have to change between the different sizes

The next problem you have is that when you start dealing with high resolution sensor, the tolerances of how exactly where the sensor must sit becomes critical. When medium format backs started getting over 17MP they started having more problems with accuracy of focus and they started getting color shifts where one side of the image would have a slight magenta color and the other side would have a slight green color. This happens because if the light enters the sensor from even an extremely slight angle, the light might pass from the color filter of the pixel next to it, so a red pixel might see a little of the light from the green filter over the pixel next to it. If the sensor is of to the left, right, up or down a little, a 100% viewfinder will be inaccurate. Many medium format cameras don't have a perfect 100% viewfinder, and companies like Hasselblad have gotten to matching tolerances between bodies and backs and not selling them separately. Basically what they do is if the mount on the body is 8 microns to thick, they sell it with a back who's mount is 8 microns too thin. They can't make every body and back perfect to the micron, but they match them up. The problem is that if you sold them separately someone might happy to buy a body and back where the flaws cancel out but they could also end up buying a body and back where the flaws are both in the same direction and make the problem even worse. Keep in mind that when I say 17MP that's on a much larger sensor with bigger pixels, when you deal with a smaller sensor like a full-frame 35mm, you'll start seeing it at lower MP.

Next, having a removable sensor is nice, but it is also a way to make it much more likely that the sensor becomes scratched or damaged. I've seen more medium format sensor scratched than 35mm sensors.

Another thing to consider is this would only be really useful if there was one standard that every camera company would agree to use, so that a smaller company like Sigma/Foveon could make 1 sensor unit that could be used in a Canon, Nikon, Pentax, or Sony. I really doubt different companies could agree to a single standard. If Nikon had their format and Nikon had their format, you could only buy what sensors they offer. Right now Canon makes and an APS-C and a FF 18MP sensor, a FF 20MP sensor, and a FF 22MP sensor. Nikon is a little more diverse at the moment they have an APS-C 14MP, an APS-C 16, an APS-C and a FF 24, and a FF 36MP sensor that are hot (as well as some legacy 12MP sensors that are on the way out, I think the 14 may be too). But they limit the number of sensors they make because every new type of sensor they make costs billions in R&D and setting up the chip foundry.

Finally let's see what we'd get out of it... keep in mind that as much as sensors improve in quality, AF, LCDs, image processing, memory card readers, metering systems, etc. The sensor is not the only piece that gets upgraded, also shutters and moving parts wear out over time and need to be replaced anyway. Trust me, I'm the first person to say I'd love to pick and choose the features I want, but it's just not practical for a large manufacturer. I could see smaller companies do this. Ricoh does it with a P&S/Mirrorless system, PhaseOne/Leaf/Mamiya and Hasselblad do it with their medium format systems, but in all of these cases, the extra connections make the system bigger and bulkier and you pay more for less than you might get from a manufacturer who deals with much larger volume.

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