Not sure about bokeh quality, but medium format digital is weak at DoF control (bokehliciousness, background blur, or degree of main subject separation from background), as well as autofocus, when compared against 35mm format. I guess it's just not the right tool for this kind of job.
This is true only if simple aperture-equivalency math is your guide. In reality there are several factors that contribute to bokeh and medium format is
clearly the bokeh winner when you look at images rather than the math.
At heart bokeh is all about visual contrast* and separation. In the same way that a white model "stands out" more against a dark background, an image with beautiful bokeh creates contrast between the look/feel of the in-focus detail and the out-of-focus-detail.
FB/BG Contrast - Most people only focus on how blurred the background is. The visual contrast of bokeh however is formed by the contrast of how sharp the detail is vs the how blurred the background is, which in turn depends on how sharp the lens is and how much resolution you have. Therefore how sharp the detail is matters
a lot. Take a
Schneider 150/2.8 LS BR lens and an
XF IQ3 100mp and shoot it wide open and you'll find it's wickedly sharp in the area of focus. Make a four-foot print from that and you'll find there is detail even when you put your nose against the print. That level of detail contrasts sharply with the super smooth bubbly buttery nothingness of the out of focus areas. This matters a lot more visually than if the out of focus areas are 5" blobs of nothing or 6" blobs of nothing (which is all the aperture-equivalence math will tell you).
Shoot a Canon 85/1.2 wide open on a small-format camera and compare it in that same print. There will be no comparison.
This is to say nothing of the
character of the lenses available in medium format. The
Contax 80/2 has such a nice and unique render and the Schneider 130/2 IMAX projector lens that I love so much has a beautiful sing-songy swirly bokeh that I love for framing objects, especially those that are in a straight line (to provide visual contrast to the swirly bokeh).
All that said, if you want only to play the math game, which as a college student studying physics I know you must love (I roomed with a physics major back in college), you can take
any 35mm lens (e.g. the famous 50mm f/0.7 Kubrick lens) and use it on an
IQ3 100mp using the electronic shutter. You just need one of the several bodies like the Univeralis that allow mounting the lens at any chosen distance, and, in some extreme cases a custom recessed lens board. The image circle of these small-format lenses is usually not much larger than the original small-format frame it was designed for, but technically you're getting a circle instead of the original small-format rectangle (and therefore a larger imaging area), and therefore your effective depth of field is shallower
.
No matter how you look at it medium format wallops small-format for bokeh.
*In case it's not obvious to other readers, by "contrast" I do not mean
tonal contrast but the more generic definition of contrast (being strikingly different from something else, typically something in juxtaposition or close association).
