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Sigma 10-20 sharpness problems with 20D and sensor already dirty!

Jet Tilton , Sep 08, 2005; 03:40 p.m.

I recently bought a 20D several weeks ago, and also bought a Sigma 10 - 20 mm F4.0 - F5.6 EX DC HSM lens, and a Tamron 28-75/2.8 lens. The Tamron 28-75 works good, but testing of the Sigma 10-20 lens revealed that even on a tripod, sharpness was not attainable. I shot in program mode, shutter and aperture priority modes, even in Manual mode, and when these photos were brought up in Elements, many areas of the photo were not sharp. I tested the lens back home, shot the houses across the street, and seemed better, but i wanted the lens for landscape shots, not neighborhood homes!

Should I return the lens for a Canon 10-22 or a 17-40/4.0 ? Or even the Tokina 12-24? Also, sensor is dirty after only 2 weeks, is this normal?

Thanks, Jet


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Dave Nelson - Atlanta, GA , Sep 08, 2005; 04:02 p.m.

The sensor was probably dirty the day it came out of the factory. It is a common problem.

It is my experience that wide angle lenses are not sharp lenses in general. Begin by stopping the lens down to f/8 and seeing if that improves your results. I would still expect it to be soft around the edges. Do a search for wide angle lenses that include examples and see if you are getting similar results.

Mendel Leisk , Sep 08, 2005; 09:36 p.m.

I started noticing a "blip" on the top edge of any image with sky. Reviewing my first shots I see it was always there. Along with about 2 dozen others, revealed by f22 shot of sky. Tried Canon's guidance for cleaning: lock up mirror and use a blower. It dislodged a few, and re-arranged a few. Atleast it did get rid of that first "blip", the one that was really noticable.

I'm just now considering Sensor Brush, and the brush and Pec paddle products of the Copperhill site.

David Lau , Sep 08, 2005; 09:47 p.m.

Sharpness is relative and subjective. Super wide normally is less sharp than normal zoom.

However, 3rd party lenses may have more QA problem than Canon. It is not uncommon that one needs to switch to get a good copy. You are lucky that your first Tamron 28-75 copy is good. I need to change once to get a good one.

My Canon 10-22 is sharp (to me) at the centre even at maxinum aperture at both the 10mm and 22mm end. For the edge, at 10mm it is poor but at 22mm it is very good at maxinum aperture. For edge at 10mm you need to stop down to f8 to get a good image.

Mark U , Sep 09, 2005; 08:45 a.m.

The Sigma 10-22 has a good reputation as a sharp lens. If your copy isn't up to expectations, it's worth exchanging it rather than paying extra for one of the other super wide zooms.

Geoff Francis , Sep 09, 2005; 10:01 a.m.

It would help if you posted some results so that we could see what you are refoerring to.

Jet Tilton , Sep 09, 2005; 05:21 p.m.

Here's my photo.net link to 2 of the test pics taken with my new 20D and new Sigma 10-20 lens, I've chosen these because they were taken on a tripod, with the self timer.


Thanks, jet

Ketil Monsen , Sep 11, 2005; 12:45 a.m.

My Sigma 12-24mm produce the same type off captures, but the pictures need a lot off USM !try

Geoff Francis , Sep 12, 2005; 10:41 a.m.

Both shots look pretty poor to my eyes. The first shot is heavily overexposed and the lighting looks very difficult, possibly causing some flare, so it is a hard one to judge. I guess I would not be happy with those shots. My sigma 12-24 produces better shots, sharper, better colour and more constrast.

Benjamin Kanarek , Sep 12, 2005; 05:49 p.m.

The Sigma is an extremely sharp lens which I have shot on the 20D and the 350D. I am a pro photographer of over twenty years and can attest to its quality. It is really quite amazing even stopped down just one stop.

You may view some samples on this forum at: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00DFLN Also check out this UK review: http://www.ephotozine.co.uk/equipment/tests/testdetail.cfm?test_id=362

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