Hi,
I agree on that. The issue is not really bokeh but short depth of field. For that you need a long lens or a large opening. The advantage of Leica is not necessarily the full format but more that they have extremely well designed lenses that actually work well at large apertures. A 90 mm lens will have the sharpness characteristics whether on a full frame or an APS-C. Normally we use bit shorter lenses on APS-C because of what used to be called the "crop factor" and that increase percepted depth of field.
Best regards
Erik
Right. That's what I was trying to get at, but I did a poor job of constructing a decent explanation in a quick post.
It's certainly not theoretically impossible to get good bokeh on an APS-C camera, but I associate the intended look with certain specific lenses that would not have the equivalent field of view on an APS-C camera as they would have on a FF camera. Trying to get that same angle of view, with the same depth of field, at the same shooting distance is not something I know how to achieve with my APS-C gear. I guess I'd need something like a 32mm f/1.8 to get the look of my old 50mm f/2 Summicron.
(My particular 50 Summicron is a bastard lens to begin with. One of the rare-earth elements inside is decomposing, supposedly due to radioactive decay or something, which I'm sure has some unpredicatble effects on imaging performance. And the coatings were ruined when I got it, so I had the front element re-polished and re-coated. I'm sure it doesn't perform like any other lens because of those things. But I like it so much that I'd buy a FF sensor camera just for that one lens, if I could afford one.)