Anyone had a Bad Canon Lense?

[Paul]

Ok, I bought a Canon 100 EF f2.8 USM in Febuary. i am starting to wonder if the lense is bad. It is almost as if when I take the print, it only focus ever other line. For instance, if you drew a bullseye on the table and photographed it, and it had red and black circles, only the red would be in focus, and the black woudl be fuzzy.

[HawgTide]

I bought the 24-105 f4L and had to return it as it was not as sharp as the kit lens that came with the 50D. Since then, I've learned to do the AF microadjustment, so that might have been part of the problem. I have the new 100 f2.8L IS and it is the sharpest lens I've ever seen. I would try the Microadjustment and if that doesn't help, then send it to Canon for testing.

[finnbay]

Agree totally with HawgTide. Had the same issue with a 100-400. Was sharp with my 40D and a bit soft on some shots with my 50D. Micro-adjusted and it solved the problem. For years I've read about photographers complaining about this lens or that lens, and although there can be "bad copies", most of the time I think it's a simpler problem that can be corrected. Newer Canon bodies can micro-adjust. However, if your have an older body or if the lens is too far out of adjustment, it may have to be sent to Canon, under warranty, to be adjusted at the factory.

[Paul]

Ok, I am going to play ignorant here. "Microadjustment" please explain what or were I find this amazing idea. I think I know what your talking about but please expound.

[finnbay]

If you have a new enough camera (I've used this on the 50D and 7D)there is a custom function for calibrating camera/lens together. On my 7D it is C.Fn III, number 5. Dan has a great tutorial for using. Good luck!

[Dbl]

Paul, one reason I like to buy local is I test each lens out on my camera bodies to make sure I am happy with their performance. I rarely end up with the first lens out of the box...My experience has been that on occasion different camera bodies perform differently with the same lens. Manufacturing tolerance, out of calibration focus systems, any number of factors can come into play.

Make sure to do some focus testing off a tripod. Do a search for focus test and you will find a couple of different charts you can print and use. If you have another camera body to use run those same tests with the lens and see if you see different results. See if you can determine if it is a lens problem, camera problem, or a technique issue. I have had a few folks complain about defective lenses and after talking about settings and looking at photos found that an adjustment to their technique made a difference. I am not saying that is the case here but if you eliminate mechanical causes by running some focus tests it will help narrow things down.

If the lens needs to go back to Canon you would be well served by sending in your body with it at the same time. They will calibrate the two together and can check your focus calibration on your body as well. It is inconvenient to be without your camera but the end result is normally worth it.

[Steve Foss]

Good advice. +2 on Dan's recommendations.

I see in the spider thread you were using a tripod as though testing the lens for sharpness.

You need to test the lens w/tripod and a stationary object that's not flat but that has enough depth that parts of it are in front of the DOF zone and parts behind it. A fairly closeup shot of a pop can with large and small writing/designs on it is one standard way to do it. Make sure the iso is high enough so you have a decently fast shutter speed and use a remote shutter release or the camera's self timer. Try some images with AF and some with manual focus.

These actions will remove all possibilities of camera/subject motion from the equation. If your images still are not sharp, you have other issues, and at that point I would send the lens and body to Canon so they can figure it out.

I have shot all the Canon tele and supertele primes, and the 100 f2.8 macro is easily one of the sharpest in Canon's whole lineup.