Blurry Canon EF 100mm f/2.8 IS
Related: Canon EF, Canon EF 100mm f/2.8L IS Macro, focus skew, lens mount / sensor parallelism, lens skew, optics, quality control, Zeiss DSLR lenses
One reader suggested that the blur is caused by the IS (image stabilization) mechanism being turned off (as is advisable for tripod use). I saw no improvement with it enabled.
I compared the third (bad) sample of the Canon EF 100mm f/2.8L IS, I to the Zeiss ZE 100mm f/2 Makro-Planar, one of the Zeiss ZF.2/ZF/ZE line which I review in depth in Guide to Zeiss ZE / Zeiss ZF Lenses. The 100/2 Makro-Planar is my reference lens.
These crops are from the left edge of the frame, the full review has left/center right and more apertures.
The Canon has a 3.1% linear advantage, but still looks like scat-like. I have no supposition that this is a design issue, rather it must needs be a badly assembled lens, the third of three bad samples.
Stopping down to f/5.6 helps of course, but the Zeiss at f/2.8 is vastly superior to the Canon at f/2.8. Actually, the Zeiss wide open at f/2 is superior to the Canon at any aperture!