Because sensor size is also part of the equation.
Eduardo
Sensor size does make a difference, but it's hot really that big of a difference because the 22MP MF sensors are still quite small.
48.9 x 36.7 is not really a big difference from 24x36. While MFD manufactures like to refer to their sensors as being twice the size of a FF 35mm DRLR sensor they are referring to surface area, not linear size. Resolution and depth of field are all dependent on linear functions not area.
So really for issues like diffraction and resolution you need to look at linear difference.
Going from a 36 x 24 to a 48.9 x 36 is actually only a 25.385 % linear increase.
This will only improve diffraction a theoretical amount of 25%
Shallow depth of field is often touted as an advantage with larger sensors as is better bokeh. However if you keep in mind that Nikon and Canon make much faster lenses this is a moot point and marketing spin.
If larger sensor or capture area is important your better off going with film that has much larger negatives.
5x7 and 6x8 cm cameras will have a visual look that is hard to match with MFD, especially if you consider that the lenses available are as fast
as MFD lenses, but with larger negatives.
For example Phase one's fastest 645 lens is 80mm at f2.8 yet their RZ67 110mm is also a 2.8.
Then there is also the issue of iris blades that drastically effect bokeh if you are not wide open.
Phase One Schneider use 5 blades and have pentagon shaped artifacts off out of focus highlights.
Nikon's 85mm 1.4 for example uses a 9 blade circular iris.
Fuji gx680 uses 8 blade circular or almost circular iris.
