Quote Originally Posted by Rob Gardner


All images shot with 70-200 f/2.8 L at 200mm equiv. on tripod with remote shutter release. All images at f/11, 100% crop to 800x600, saved in Photoshop as JPG with 10 image quality. 50D was calibrated with AF Microadjustment set at max (+20) - could probably use to go farther.

Rob,


1) How was the 50D calibrated? It appears to me that the body/lens is back focusing badly.


2) At f11, DLA(table in the MkIII review)has a negative effect on the IQ of the 50D. Because of the pixel density of that sensor diffraction begins to effect IQ at f7.6 ABC (According to Bryans Calculations). Diffractionblur is not noticable on the 1D MKII until f12.7 ABC. Bryan illustrates effects of diffraction on the 50D here.


I would really like to see a comparison using a focus chart. Try this one at larger apertures like f4-f8. Tim Jackons D70 Focus Chart Follow his setup as closely as possible. This reveals quite a bit about a len's performance.


When you post your results, try posting 100% crops 240-300 pixels wide in a side by side format. It's much easier for people to compare. It's a shame we don't have a way to do overlays like Bryan does.


Thanks for sharing your test data and thoughts. I hope you will continue to test your equipment to find it's strengths and weaknesses. It is a noble endeavor.