In another thread, someone posted the link to your tool for calculating the print size. It's an interesting tool.
I think you have a very basic mistake. You assume every pixel is equivalent from camera to camera?
You tool shows Leica C can produce larger print out than Leica M8.2. Really? Where did you get that idea?
Hi,
The tool uses human visual acuity as the limit of resolvable detail. Pixels are not the basis. Given that (angular resolution) limit, because it is also influenced by contrast and illumination level. Those are not added to the equation, I assume optimal viewing conditions. Under worse conditions the resolution will be even lower and we could magnify more (as long as viewing conditions cannot become better).
How we sample the original scene, i.e. which lens and sensor we use is relatively unimportant for the detail that we cannot resolve by eye anyway. When detail is smaller than we can resolve by eye, its quality is not relevant. However, for the detail that we
can resolve by eye, the pixel quality does matter. But also output sharpening matters, in fact the MTF curve of the entire optical chain (lens, sensor, Raw conversion, post-processing, output modality, viewing conditions, eye) is what will determine the visual impression.
The choice of sensor (amongst others) will therefore indeed make a difference, but only for the detail that we can ultimately resolve by eye.
The sensor dimensions and sampling density also do not factor in lens quality, but they are simply used to set a physical limit to the COC that can be used. A COC smaller than the sensel will not change the DOF, the sensel size dictates (and assumes a large fill-factor). The same applies to diffraction, when diffraction becomes an absolute limit for high spatial frequency detail (=low contrast) the COC will be adjusted even if the sensor could resolve more detail (detail is missing in the sensor's input signal).
So there are many more factors that come into play, but once we can no longer resolve details by eye they become less relevant. 'Sensel quality' also equates to a different Capture sharpening requirement (as outlined in
this thread), which will even out some of the differences because Capture sharpening should restore the original input signal (in the original scene) as much as possible.
Cheers,
Bart