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Gotcha @ reason for reply. I didn't specify which aspects I was agreeing with, my bad.
that a larger format lens does not need to deliver the resolution of the smaller format lens, because the larger image area compensates for the loss. And I agree with that.
Imo, this is likely something that I think we can all agree that the larger area affords some offsetting compensation potential. However, just because that potential affords lesser resolving MF lenses some compensatory benefit, it does not mean that MF lenses are necessarily less sharp. As noted by Jim's data, herein lies a mixed bag of myth and truth, with the myth that MF glass is always less sharp being the challenging part for many folks to re-consider.
For each format there is variation in lens performance, and the better lenses for a larger format may be more than useful on a smaller format, certainly if the step is relatively small, such as from 645 to 24x36 mm. I am, however, not tempted to mount an 8x10" lens on my mobile phone, for more than one reason.
+1 ... but I am tempted to construct a mount so I can shoot some of my Graflex glass on FF.
As the difference in format increases, you will also find that the maximum aperture of the lenses (for the larger format) decreases, in order to permit a reasonable image quality at a reasonable price. A direct comparison with a lens for a much smaller format is then only possible at apertures that hit diffraction, i.e., the comparison is not very meaningful.
+1 @ diffraction vs. physical aperture diff's between format/area (back to formula). While people often use this to refute why they can't be "equivalent" @ direct comparison, it also offers properties to be harnessed in the inverse/opposite utilization (i.e. stopped down vs. w/o) regarding diffraction/aperture relationships. All along, I've not really tried to present "equivalent" comparisons. It is this very fact that they are different that is something that can be harvested/harnessed to render a more MF look than you may be getting from FF glass, even if only on FF. I've only tried to suggest that the look of the projection remains the look of the projection.
Further, it seems that people mean different things by "medium format look" and that the discussions in this thread are clouded.
+1 @ ill-defined "MF Look" ... I like the smoother transitions that is projected (trig) and the well corrected optics created by the engineer/designers. Meahwhile, others may think that DOF is the holy grail of the MF look. When I want a lens that renders a subject with more micro-contrast, I'll grab for something other than my M645 glass.
I shoot a mixed bag of FF and MF, as well as a mixed bag of Oly, Nikon, Canon, Leica, Zeiss, Tamron. It's highly unlikely that you'll ever get me to say that any one of my lenses is better than another, as they all project different images with different "looks" that encompass the range of micro-contrast to color to bokeh to corner resolution to center resolution (Nikon vs. Oly @ notable) to CA to etc.. These differences exist within a format and across formats.
Now, I might say that Oly has bettter resolving corners in their 28/3.5 than the Nikon 28/2.8 AIS, but the Nikon has more central resolution in Zone A than Zone C. But, I likely won't say that the Oly is better than the Nikon when I'm wanting a lens that projects a contrasty central image. Neither will I say that the Nikon is better than the Oly when I want Oly colors. So it goes also, with FF glass vs. M645 glass at producing a different "look". The MF glass produces a more MF look than FF glass (design @ trig) and that can be captured (even if only the central crop).
Given the choice @ the marginal 33x44 vs. 24x36, I simply decided to to use the M645 glass which was designed to cover the larger 60x45 film area, even if only capturing 36mm at the most, whereas the most I could capture with the medium format sensor is 44mm. This represents about 20% diff in capture area, but, imo a projection that is more than 20% different in garnering the MF look because of its design to cover the larger area.
This is the reason that I suggested to the OP that if he didn't like the jump to only 33x44 for "yesterday's" medium format (or today's digital 645), he could still get some of the MF goodness from the projected imagery of MF glass, if willing to concede the difference between 44mm vs. 36 mm. Imo, this 20% difference amounts to debating a 16MP sensor vs. a 20MP sensor. It might sound like you're giving up a lot ... but are you really giving up a critical amount And is that 20% in real estate really the reason for the "look" of the larger format, or is it the projected image?
I realize that this still will likely not "convince" many folks of very much. But, I'm not really trying to convince anyone ... just explaining why I like MF glass on FF, even if it is going against the conventionally established. In a "regular" forum, I wouldn't ever mention it or waste my time, energy or breath on such things with people who I know would never appreciate any of this... but this is the Alt Forum, and this is FM (complete with one or two lurkers).