Is my EF-S 17-55mm a lemon?

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Thanks for taking the trouble! Can see them now. :D
Please correct me if i'm wrong but I can see a fair bit of CA in your test pics too. Did you take the crop on the right side of the picture? Your yellow fringing is on the right and mine on the left. This might actually be the behaviour of this lens huh?

One interesting thing I found out is if I increased the distance of the sensor to the subject, the CA reduces to almost nil. I guess this lens isn't very good at close distance?

Calebk: Yeah, I'm skeptical of an exchange although it's still within the 7days period. But I guess my argument is probably not strong enough for an exchange. :dunno: Might still give it a try though. Probably request to test another copy to see if it gives the same result.

Depends on the shop you buy it from. I have no experience with CP so cannot comment. I bought the 17-55 from another shop in 2007. Found there was a problem with back-focus and returned it to the shop within 4 days. No questions asked. The guy went to the back room and came out with another copy and asked me to test and take that if I am happy with it. Now that's what I call service. I still shop there even if the price is a little tad higher.

I got a feeling that the 17-55 is a difficult lens to manufacture because the combination of the zoom range and fast aperture requires very tight manufacturing tolerance. Same reason why the 70-200 mm f/4 has less 'issue' than the f/2.8 version (note the quotes).

To TS - no harm trying to find out if you can exchange the lens. Maybe bring along the test chart and laptop. I suggest if you are doing that, do it during off-peak. Watch out for front or back focus when testing the copy.


Since your using 40D, can you try to use live view with 10X zoom and use manual focus? I had a similar problem with my 135 it was back focusing and causing the CA.


You mentioned that you did the test at "around" 40cm. And that if distance increases, the CA reduces. The close focus distance of the lens is 35cm. There is a chance that when you did the test, it might be very close to the "limits" of the lens, and maybe exceeded it's intended operating range, that's why the CA appears. There maybe a chance that there is nothing wrong with the lens.

Just a comment.;)

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