I think that's a bit of a confused question: In response to xiota, it's important which of the distances between the flange and focal plane (FFD) and the distance between the rear and the focal plane is the smallest. This is why, for example, customized SLR lenses stand out in mirrorless cameras (the rear elements of SLR lenses need to clear the mirror, which is not the case with special mirrorless lens designs).
It is possible to see this by simply comparing FFDs for different mounts. There is a comfortable table here.
- Fuji X mount is 17.7 mm
- Sony E-mount is 18 mm
- M4 / 3 is 19.25 mm
- Mount M is 27.8 mm
- Pentax K is 45.46 mm
- Nikon F is 46.5 mm
- Canon EF is 44 mm
It immediately shows that you can not assemble, no matter what you do both a lens from the short end of this list and a lens from the long end of this list, without any of them protruding far from the body, unless you are doing something absurd, as if you were inserting the mounting flange many millimeters into the body.
Although this is not a problem, simply moving the sensor in the camera body is also extremely inconspicuous. Sensors are thicker than films and have electronics that have to go somewhere. Almost all the cameras behind the sensor must also attach the screen to the back of the camera, which also requires support and electronics. You can see the differences when you compare camera designs where film and digital bodies are the same. A good example is M-mount cameras:
- the M3 is 33.5 mm thick;
- the M6 is 33.5 mm thick;
- Like the Minolta CLE, the Leica CL is 32 mm thick.
- The Zeiss ZM is 32 mm thick.
It looks like the thinnest movie M-mount camera is about 32mm tall: I suppose the Leicas are a bit thicker because they're more robust. If one compares this with the above-mentioned FFD for M-mount, there is not much room for maneuver here.
Now look at the digital Ms:
- the M8 is 39mm thick (not full size)
- The M9 is 37 mm thick
- The M10 is 39 mm thick
The mounting flange of a film M-mount camera is substantially flush with the front of the camera, so the digital Ms are not thicker because the mount is moved back further into the housing: they are thicker because the sensor is behind and behind the mount assemblies the support arrangements for the screen take up more space than films. If you look at the above dimensions, we can assume that & # 39; more space & # 39; somewhere around 5-6 mm (and we can also deduce from the M-mount FFD that the film, the printing plate and the back of the camera are on an M6, for example) is a bit under 6mm all in: it's pretty easy to confirm that this is true for most movie cameras, of course, by opening the back and measuring the thickness of the film).
Of course not now knows that it is not possible to make things thinner. But I think it's pretty clear that if Leica could do it, they would do it – there were a lot of negative comments about the size of the digital woman. We know that they get sensors tailored to their needs (since they produce cameras with monochrome sensors). So you talk to the sensor manufacturers. So it's hard to make that thing thinner.
If we put this together, we can see a few things.
- It is not possible to mount lenses with very different FFD distances on the same body, without one of them having a -adaptor that protrudes far from the body (or sinking one of the brackets far into the body) I find absurd). In the case of e-mount, for example, there is a difference 26 mm – more than an inch – between his FFD and the Nikon FFD.
- The sensors and their support arrangements (including the back of the camera, the screen, etc.) appear to be at least about 10 mm.
- A camera that can mount a Nikon SLR lens with the mounting flange flush with the housing must therefore be about 54 mm thick.
It is then difficult to find dimensions for cameras, as they often contain different handles. However, the Fuji X-Pro 2 should be about 35 mm thick at the thinnest point, which looks a bit thicker than it needs to be (compare the FFD for their lenses, 17.7 mm with the FFD for M-mount lenses from 27 , 8 mm) The M9 is 37 mm thick and you can see how much work Leica must have done to make things thin. To mount a Nikon SLR lens on an X Pro 2, the camera must be nearly 20 mm thicker. That's probably not a compromise someone wants to do.