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

Discussion in 'Canon EOS' started by jet_tilton, Sep 8, 2005.

  1. 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
     
  2. 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.
     
  3. 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.
     
  4. 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.
     
  5. 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.
     
  6. It would help if you posted some results so that we could see what you are refoerring to.
     
  7. 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.

    http://www.photo.net/photodb/member-photos?user_id=1574581

    Thanks,
    jet
     
  8. My Sigma 12-24mm produce the same type off captures, but the pictures need a lot off USM !try
     
  9. 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.
     
  10. 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
    00DXFG-25630184.jpg
     
  11. In observing your two images, it seems that the sensor is fogged or perhaps the mirror had condensation and left some residue on the mirror and perhaps the sensor as well. It does seem like the type of refraction associated with that type of anomoly. I clean my sensor with a flat plastic utility using lens cleaning tissue which I tape on the plastic flat stick and only use my breath condensation to remove any residue. I have used this successfully. Benjamin Kanarek http://www.figure.fr http://anashcreation.com/thenashgallery/BenjaminKanarek
    00DXFo-25630584.jpg
     
  12. FWIW

    I tested my new Sigma 10-20 last night. I can confirm Benjamin's view above. It is an excellent lens and very sharp. It compares well with my Sigma 18-50 f2.8 EX DC which is also very good. The images you have posted are definitely well below what should be achievable with this lens.
     
  13. I've tried a couple of Sigma 10-20's with varying results. The first 2 weeks ago was Sigma UK's demo copy which would not let me take photos below 14mm and massively over exposed pictures in the P-mode. The second I subjectively tried yesterday at my local Canon dealer, in comparison with the Canon 10-22, Sigma 18-50 and my 300d 18-55 kit lens.

    The 10-22 is somewhat sharper and gives faster shutter speeds for the same Av than the 10-20, which still over exposes little at -2/3EV but has a wider FOV (Zoombrowser indicates 17mm at the 20mm setting) and shows less perspective distortion.

    At the focal lengths that overlap, the Sigma 18-50 is as sharp as the 10-22 (while still over exposing a little), whilst my kit lens, which seems a good copy and sharper than my 50/1.8 prime (!), is the same as the 10-20.

    I'm not a manual setting expert, so all settings were what the 300d gave, but subjectively the 10-22 is the best, but it isn't worth the ?170 ($300) price difference in the UK - now if I can convince my son to buy the 350d with it's ?75 discount voucher, then the 10-22 it will be.

    All the best...Tom P.
     

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