I made some comments on another photography site about the new Leica S 007 being a medium format camera (ok, it is). My point was that the old definition of Medium Format being anything larger than 135 sized sensor is not really relevant in the digital age.
During the film era things were simple: with the same or similar emulsions available in different sizes, you were able to increase the IQ simply by using bigger piece of film. With that came the effect of diminishing DOF with the same aperture lenses, etc. The MF look, if you wish. And LF look with large plates.
If we put this "scientifically" the formula which defined the "look" had only two variables: film size (which governed the IQ) and the lens aperture, larger formats having less DOF.
Now we have another variable in the equation: Sensor quality. Sensors can not be judged by surface area only, like film was (in a simplified sense). This makes the "format equation" much more complicated, because we can get the same MF quality with small but high resolution sensor with large aperture lenses. So a 135 size sensor (like Nikon D8xx, Sony & new Canon) with fast lens can give you optically the same picture as slightly larger "mid format" (?) sensor with slightly slower lens, as larger format lenses tend to be. As we know, new 135 sensors beat many MF backs and sensors both in resolution and all in DR. With a slightly faster lens all shallow DOF effects of MF cameras can be duplicated with smaller sensors also.
So are we stuck with the old film era definition of MF? How about defining digital MF as something with more than certain resolution (30 MPix?) and the availability of lenses for the system which give the same minimum DOF as f/1.4 on a 135 sensor, or f/2 on a "MF" sensor (whatever it is)? It should be the end result that matters, not the way it is achieved.
Hello Petrus,
Since digital age, marketing started to be very strong to sell everything under every name possible (if not trademarked). In my world, medium format start at 6x6 cm of film or digital sensor... So, IMHO, digital medium format are not yet proper medium format cameras because it seems to never exceed 53.7 x 40.3mm so 5x4 cm. Yet it is pretty close so lets call it medium format. Every thing under 5x4cm is called crop, it is something new in between, proper to digital age. I would not call it medium format.
For some schools and teachers, pixel count have nothing to do with what we call medium format. What count is perspective of a subject on a certain sensor surface, so roughly a kind of visual rendering. Same goes for Large Format, another rendering. It is vain to try to mimic those specific rendering between formats. It is maybe possible with photoshop (certainly but at a cost: time).
The less the enlargement, the better the picture.
Pixel count is secondary in this story. It just improve what can be done in the picture but at the end the global rendering is given by the format, not the pixel count. It is why I continue to give, even today, all credits to film, all my attention to the format and the format only (especially in digital).