You may remember my complaint about RAW shooting a cell tower 1/2 mile away and getting blurry images, esp. at 100% in ACR using cheap Sigma glass. Well, I repeated the experiment using a Canon 17-85 f/4-5.5 IS on my Rebel xti. It was like the lights were turned on. Throughout the setting range, the Canon stayed clear to well over 100%. Pixelating, that had occured at 200% with the Sigma, didn't occur until 400% with the Canon glass.
Can this problem be fixed except by pouring more dollars into the glass, I'm trying to avoid buying the Canon 70-300 f/4-5.6 IS as well as the one listed above?
Well, you could buy second-hand glass... or you could stop looking at your photos at 400%. Assuming your monitor is capable of 96dpi, a 400% zoom is like looking at a 24dpi print. Assuming you use the full 3888x2592 resolution your camera is capable of, this means making a 4x2.7m
print... are you really going that large?
(sort-of joking, I'm really happy I've spent quite a lot of euros
on good Canon glass)