Fuzzy 24-105L

[Greg D]

Hello folks.
I've read the thread on the soft 24-105 from a week or so ago, but decided to post a new one, as my problem may be a bit different (my shooting's certainly not in that league!).  Anyway, I recently bought a 24-105 to replace a 28-135 IS and Sigma 17-70.  Thought I could replace 2 lenses with 1, and get better quality to boot.  I wasn't expecting miracles, mind you, but I sure didn't expect it to be worse, which it is.  To confirm that it wasn't my imagination, I shot several identical shots (same focal length & aperture, on tripod with mirror lock-up) with the 24-105 and a 70-300 IS (which seems to me quite sharp), and the difference is very clear.  The 24-105 is much softer everywhere, not just by a tiny bit.  Again, I'm not expecting perfection - I'm comparing this to other zooms which one would expect to be inferior, (and shooting with a 450D BTW).  I don't think it's a focus problem, since manual focusing seems to yield the same result.  Any ideas?
Thanks much

[Alistair]

Unusual, the 24-105 is widely regarded as pretty sharp. You may have a bad copy or perhaps you left IS turned on when on the tripod and got a bad reaction to that. Hard to tell. Any chance you could post and image or two so we can see the problem? May help in diagnosing it.

[ErikKaffehr]

Hi!

Just a couple of hints...

- Take a picture of a brick wall, compare corners. If some corners are sharp and some not it may indicate a serious decentering problem.
- Take pictures with different apertures and compare
- Check if your lens has front or back focusing

If you bought your lens from a firm you should be able to return it if it is faulty.

Best regards
Erik

Hello folks.
I've read the thread on the soft 24-105 from a week or so ago, but decided to post a new one, as my problem may be a bit different (my shooting's certainly not in that league!).  Anyway, I recently bought a 24-105 to replace a 28-135 IS and Sigma 17-70.  Thought I could replace 2 lenses with 1, and get better quality to boot.  I wasn't expecting miracles, mind you, but I sure didn't expect it to be worse, which it is.  To confirm that it wasn't my imagination, I shot several identical shots (same focal length & aperture, on tripod with mirror lock-up) with the 24-105 and a 70-300 IS (which seems to me quite sharp), and the difference is very clear.  The 24-105 is much softer everywhere, not just by a tiny bit.  Again, I'm not expecting perfection - I'm comparing this to other zooms which one would expect to be inferior, (and shooting with a 450D BTW).  I don't think it's a focus problem, since manual focusing seems to yield the same result.  Any ideas?
Thanks much

[Greg D]

Unusual, the 24-105 is widely regarded as pretty sharp. You may have a bad copy or perhaps you left IS turned on when on the tripod and got a bad reaction to that. Hard to tell. Any chance you could post and image or two so we can see the problem? May help in diagnosing it.

IS was turned off.  I'll try to post shots.  Might take awhile (on dial-up!).

[Greg D]

Hi!

Just a couple of hints...

- Take a picture of a brick wall, compare corners. If some corners are sharp and some not it may indicate a serious decentering problem.
- Take pictures with different apertures and compare
- Check if your lens has front or back focusing

If you bought your lens from a firm you should be able to return it if it is faulty.

Best regards
Erik

Thanks for the ideas -
 - The test shots I took (and will try to post soon) were not of a brick wall, but a wooden one (filling the frame).  They were shot (with both lenses) at 70mm and f8, (CW average metering and -1/3 EC - my "default" settings), IS off, on a tripod, without moving it between shots.  On looking at the corners, they don't seem much worse than the center - it's soft everywhere.  (Of course, it's a 1.6-crop camera.)
 - I took more shots at different apertures of foliage (something where DOF was an issue) and again, everything was soft.  Of course the the center (intended focus) was sharper than elsewhere, but if it was a front/back-focus issue doesn't it follow that SOMETHING in the shot (in front of or behind the subject) would be sharp?  That wasn't the case.
I don't know exactly what a decentering problem is - would that be a grinding flaw in a lens element?

Thanks much

[Greg D]

Thanks for the ideas -
 - The test shots I took (and will try to post soon) were not of a brick wall, but a wooden one (filling the frame).  They were shot (with both lenses) at 70mm and f8, (CW average metering and -1/3 EC - my "default" settings), IS off, on a tripod, without moving it between shots.  On looking at the corners, they don't seem much worse than the center - it's soft everywhere.  (Of course, it's a 1.6-crop camera.)
 - I took more shots at different apertures of foliage (something where DOF was an issue) and again, everything was soft.  Of course the the center (intended focus) was sharper than elsewhere, but if it was a front/back-focus issue doesn't it follow that SOMETHING in the shot (in front of or behind the subject) would be sharp?  That wasn't the case.
I don't know exactly what a decentering problem is - would that be a grinding flaw in a lens element?

Thanks much

 Well no luck uploading pics.  When I hit the upload button it tells me I didn't select a file for uploading (I'm quite sure I did - it appears in the field).  One did upload, but not much use without the other.  If I'm missing something here maybe someone will clarify for me.........

[ErikKaffehr]

Hi,

Decentering is a problem in manufacture. It essentially means that some part of the optical system not aligned to the optical axis. Decentering may be quite common. If a picture is much sharper or unsharp than the others when taking a perpendicular picture of a flat target it is a very good indication of manufacturing error.

From your writing I get the impression that you have a very bad sample, so I think that you should either send it back to whoever sold it to you and ask for a replacement or send it to Canon for service. The 24-105 is known to be a very good lens, so I don't think that your results are typical.

Best regards
Erik

Well no luck uploading pics.  When I hit the upload button it tells me I didn't select a file for uploading (I'm quite sure I did - it appears in the field).  One did upload, but not much use without the other.  If I'm missing something here maybe someone will clarify for me.........

[Greg D]

Hi,

Decentering is a problem in manufacture. It essentially means that some part of the optical system not aligned to the optical axis. Decentering may be quite common. If a picture is much sharper or unsharp than the others when taking a perpendicular picture of a flat target it is a very good indication of manufacturing error.

From your writing I get the impression that you have a very bad sample, so I think that you should either send it back to whoever sold it to you and ask for a replacement or send it to Canon for service. The 24-105 is known to be a very good lens, so I don't think that your results are typical.

Best regards
Erik

Thanks much.  That's kind of what I concluded.  It'll be on its way back tomorrow.

[Greg D]

[quote name='ErikKaffehr' date='Nov 12 2008, 09:39 PM' post='236562']
Hi,

Decentering is a problem in manufacture. It essentially means that some part of the optical system not aligned to the optical axis. Decentering may be quite common. If a picture is much sharper or unsharp than the others when taking a perpendicular picture of a flat target it is a very good indication of manufacturing error.

From your writing I get the impression that you have a very bad sample, so I think that you should either send it back to whoever sold it to you and ask for a replacement or send it to Canon for service. The 24-105 is known to be a very good lens, so I don't think that your results are typical.

Best regards
Erik


One final question:  Am I wasting money putting a lens like the 24-105L (assuming I get a good copy, that is) on a camera like mine (Rebel XSi aka 450D)?  As I said in the first post, I'd been using a 28-135 IS and a Sigma 17-70 and was not unhappy with the results.  I went to the 24-105 to replace two lenses with one, and thinking that potential better image quality would be a bonus when I learn what I'm doing.  Am I kidding myself?
Thanks for any opinions.

[BruceC]

One final question:  Am I wasting money putting a lens like the 24-105L (assuming I get a good copy, that is) on a camera like mine (Rebel XSi aka 450D)?  As I said in the first post, I'd been using a 28-135 IS and a Sigma 17-70 and was not unhappy with the results.  I went to the 24-105 to replace two lenses with one, and thinking that potential better image quality would be a bonus when I learn what I'm doing.  Am I kidding myself?
Thanks for any opinions.

I sometimes use the 24-105 on a 400 body.   It's not wide enough for me as a walk about lens on the crop body.   It's great on Full Frame.  $1000 is a lot to spend if you don't love it.  I'd say return it if you don't have full frame.  Maybe sell the 28-135 and get a 70-200.

Did you return or swap it yet?

[Greg D]

I sometimes use the 24-105 on a 400 body.   It's not wide enough for me as a walk about lens on the crop body.   It's great on Full Frame.  $1000 is a lot to spend if you don't love it.  I'd say return it if you don't have full frame.  Maybe sell the 28-135 and get a 70-200.

Did you return or swap it yet?

Returned it to Canon a few days ago.  As far as focal length range goes, I more often find myself unable to frame as tightly as I'd like rather than the reverse.  So in that regard, the 24-105 is fine even on the 450D.  And I have a 70-300 IS I'm happy with for longer lengths.  I'm just wondering if, image quality-wise, the camera can't keep up with the lens, so to speak, and so the lens is a waste in that regard.