Why are some lenses with an image stabilizer sharper than the non-IS version, and others are just the opposite? I can't believe it's just the implementation of said stabilizer. Take the different versions of 70-200mm in both the f4 and f2.8. Same focal range, but opposite results. Is it a price issue? When making a product, you set a time/price limit. Maybe they reached the max value before finishing the fine tuning. Could it have been a bad copy or two that was used it the test for the site? He's pretty meticulous. If I was thinking ahead, I would have checked to make sure the IS system on the two versions of the 70-200 were the same, and also took the f2.8 model to f4 and seeing if it followed the same pattern. Just curious.