Here is a quick test I did ....
I did a little comparison between my Fuji GX680 250mm f5.6 and the Canon 200mm F2.8L Mark II @5.6.
I used the Canon 5d Mark II for the captures. To capture the Fuji lens images I held the Canon 5D II behind the Fuji 680 body.
I expected the Fuji lens to be somewhat inferior as it is about 20 years old and has an image circle of about 200mm while the Canon has an image circle of 50mm
well it was quite interesting...
Here is a 100% crop (scaled down by Flickr) from the Fuji/Canon capture (sensor placed to the right of the lenses center):
And here is the same from the Canon/canon capture
Quite amazing how well the Fuji compares, especially considering that the Fuji is shooting at full aperture while the Canon is shooting stopped down two stops ... at 5.6 that is it's best aperture.
Here are the full frames:
See how the Bokeh on the Fuji is nicer and you get it already at 5.6. This is important to me as I like to shoot at slowish shutter speeds so that I can get some movement such as a dress or hair in the wind.
Then if you consider ontop of that the fact that if I was using the full frame I would be closer to the bush and would have even better bokeh on the background.
Throw in the higher dynamic range of film especially in the highlights and it's a formula that I like.
And one other thing. When running the images of the Fuji/canon and the Canon/canon through the JPEG compressor the Fuji lens files always came out larger indicating that there is more information in the Fuji lens images.
One thing that this test clearly indicates one interesting thing. If you consider that the Fuji lens when using the full 6x8 frame will be projecting about 6x more information..... well it indicated that for now only film gives you the opportunity to capture these large format images projected by these unique lenses.
Here is a diagram to show how little of the full frame the Canon was capturing:
And just to give an idea of how sharp the Canon 200mm 2.8L II is (and how damn cute my son was... he's 6'4" now
Shot at 2.8