I frequently read this sort of thing in lens reviews: "Diffraction limiting begins to set in at /8, though it doesn't impact on sharpness until /16; even at /16, we're seeing only 2 blur units across the frame. Using the /22 aperture setting produces a softer image, at 3 units across the frame." That's a review of a Canon superzoom lens on a 20D. But my understanding is that where diffraction sets in is entirely a matter of which camera body you're using. It's all about pixel size and aperture, regardless of the lens, as explained here. On that page, they state, "the Canon EOS 20D begins to show diffraction at around f/11." How do I reconcile this statement with the lens review above? Now I understand that some lenses just aren't that sharp and will show their softness before the camera itself is experiencing diffraction, but that situation doesn't seem to be what the review above is describing. Or is it? Here is an excerpt from another review: "As you stop down, diffraction limiting seems to begin setting in somewhere between f/8 and f/11, depending on focal length and the size of the pixels on your DSLR body." Depending on focal length?? Are they saying that (in this case) the Canon 70-200mm f/2.8L is not sharp enough to out-resolve a 20D at f/8-f/11 at some focal lengths? I'm confused.