Cross-posting from Reddit. There are probably more Canon users on this forum.
I recently bought a Canon 100-400 L IS to go with my 6D. Based on the reviews it looks like on the 6D it should be better than my 55-250 IS on my T3i, and almost as good as the highly regarded 100-400 II without having to spend $2k. But I've done some tests, and it doesn't look any better than what I had before. My 55-250 is much sharper than my 100-400 in the corners, and the same or slightly better in the center. But the 55-250 has a bit more CA and a bit lower contrast.
Here's my comparison: http://imgur.com/a/K5aAy
The 100-400 is on the left on my 6D. 400mm f/5.6 1/25 sec ISO320.
The 55-250 is on the right on my T3i. 214mm f/5.6 1/15 sec ISO800.
Is the 100-400 supposed to be this soft in the corners? Or did I get a bad copy? It's kind of disappointing to spend 8x as much ($800 used vs $100 used) on a lens and get worse results.
I adjusted the exposure of each in LR to be about the same, so don't compare the exposure settings above, but I applied no other adjustments and set sharpening to 0. The setup is not ideal, and the light is not that great. I left the tripod in the same position for both shots, except for re-aligning slightly. The chart is printed 11x17 size on plain paper, and it's at the size and resolution limit of my printer. I tried printing it on 8.5x11 paper, and the finest lines aliased despite setting "4800x1200 DPI equivalent" resolution whatever that means. The test chart is a vector PDF I found online. The distance from the camera to the chart is about 15 feet. A real test chart, longer working distance, better lighting, better alignment, sturdier tripod, etc would be nice, but I don't think it's necessary since I can get good results from the 55-250 and from the center of the 100-400
Here's The-Digital-Picture's comparison (with the 55-250 STM selected because that looks the most like my 55-250). http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=856&Camera=736&Sample=0&FLI=5&API=1&LensComp=113&CameraComp=453&SampleComp=0&FLIComp=7&APIComp=0 Note that the TDP test chart is twice the resolution of mine, and they have a much better test setup. (http://www.the-digital-picture.com/Help/ISO-12233.aspx)
I recently bought a Canon 100-400 L IS to go with my 6D. Based on the reviews it looks like on the 6D it should be better than my 55-250 IS on my T3i, and almost as good as the highly regarded 100-400 II without having to spend $2k. But I've done some tests, and it doesn't look any better than what I had before. My 55-250 is much sharper than my 100-400 in the corners, and the same or slightly better in the center. But the 55-250 has a bit more CA and a bit lower contrast.
Here's my comparison: http://imgur.com/a/K5aAy
The 100-400 is on the left on my 6D. 400mm f/5.6 1/25 sec ISO320.
The 55-250 is on the right on my T3i. 214mm f/5.6 1/15 sec ISO800.
Is the 100-400 supposed to be this soft in the corners? Or did I get a bad copy? It's kind of disappointing to spend 8x as much ($800 used vs $100 used) on a lens and get worse results.
I adjusted the exposure of each in LR to be about the same, so don't compare the exposure settings above, but I applied no other adjustments and set sharpening to 0. The setup is not ideal, and the light is not that great. I left the tripod in the same position for both shots, except for re-aligning slightly. The chart is printed 11x17 size on plain paper, and it's at the size and resolution limit of my printer. I tried printing it on 8.5x11 paper, and the finest lines aliased despite setting "4800x1200 DPI equivalent" resolution whatever that means. The test chart is a vector PDF I found online. The distance from the camera to the chart is about 15 feet. A real test chart, longer working distance, better lighting, better alignment, sturdier tripod, etc would be nice, but I don't think it's necessary since I can get good results from the 55-250 and from the center of the 100-400
Here's The-Digital-Picture's comparison (with the 55-250 STM selected because that looks the most like my 55-250). http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=856&Camera=736&Sample=0&FLI=5&API=1&LensComp=113&CameraComp=453&SampleComp=0&FLIComp=7&APIComp=0 Note that the TDP test chart is twice the resolution of mine, and they have a much better test setup. (http://www.the-digital-picture.com/Help/ISO-12233.aspx)

