Roger at LensRentals.com has done a quick comparison of the EF 400 f/4 DO IS and EF 400 f/4 DO IS II as well as the EF 100-400 f/4.5-5.6L IS and EF 100-400 f/4.5-5.6L IS II.
From LensRentals.com on the EF 400 f/4 DO IS II
|400mm DO mtf50||400mm DO II mtf50|
“The difference in Canon's computer-generated MTF charts for the 400mm DO and 400mm DO II is pretty striking, and I think our results confirm that difference shows up in actual optical testing as well as in the computer ray tracing. Canon also says the new design has much greater contrast, and I tend to believe that too, although we'll all want to see images in a variety of lighting conditions.”
From LensRentals.com on the EF 100-400 f/4.5-5.6L IS II
|100-400mm mtf50||100-400 II mtf50|
“The Canon computer-generated MTF charts suggest that the center of the image should be similar in both the old and new versions, but that the Mk II should be noticeably better off-axis and particularly in the corners. We do see that difference in the resolution tests, but I had expected the difference to be a bit larger. It's certainly not nearly as dramatic as the DO difference.”
Read the full comparison at LensRentals.com