Variations of same lens

Lenses aren't dead nuts accurate. Even L glass. There is a limited amount of variation in focus that is allowable in bodies and glass. So say your camera is a 0 (perfect focus) and your lens is a +3, then the glass may seem soft. If your body is a -3 and the glass is +3 then it will seem very soft.

Bodies like the 7d have a setting for each len that you can micro adjust the focus for to make all your glass "work" correctly in correlation with YOUR body.

My question is, are you noticing problems or are you just paranoid because others have seen problems? Put your camera on a steady tripod, set your aperture to 5.6 or smaller, do a critical focus and take a picture. Look at that picture and see if it is sharp. Most glass isn't as sharp wide open as it is stopped down. If you see no issues, your lens is fine.

Also, especially with any body 7d and under, don't pixel peep and look at your image 100% because you will always be disappointed. I have a 7d and about $10k in glass and if I always looked at 100% I too would wonder where my money went. It is just something you don't do. And my pictures print super sharp at 12x18. But on the computer pixel peeping they don't look as good.

Barnzee said:

they got a defective lens, but It is hard to identify

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If you can't identify the problem, then you don't have to worry about it. The only time you have to worry about a defective lens is if you can actually tell there is a problem with the lens.

Also, as someone said about the focusing being off, that can also be a slight problem. Canon will let you bring in the camera and lens and they will calibrate them for free under the lenses warranty.

Barnzee said:

My Question is that since I'm an Amateur I really wouldn't be able to verify whether its defective, what should I look for?

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The biggest issue will be focus, so lay down a ruler facing away from you and focus half-way down. Take a picture and see what's in focus. If possible, use a tripod.

Paul