AF Adjustments?!

Discussion in 'Digital Photography' started by finnschi, Jan 28, 2010.

  1. finnschi macrumors 6502

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    #1
    I want to a professional Canon shop today, and ask them about Back/Front focussing errors on my Sigma lenses, they told me that it is very expensive for my old camera to fix this (20D) and its much easier on the 7D/5Dmk2 because they have some Af adjustment screw :confused:

    does anyone know what this is all about :confused: because my 24mm Sigma does have a slight back focussing problem?

    also is this "screw" aviable on the 50D as wel?
     
  2. jampat macrumors 6502a

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    Mar 17, 2008
    #2
    50D/7D/5D Mkii have software correction for back/front focusing. You put the lens on, then adjust in the menus to correct where it focuses. It is not a physical screw.

    If the lenses are new and way out, people send them back to sigma and hope for a better copy the second time around.

    You can also send away all of your lenses and your body and get them calibrated (important to send everything).

    Each lens has some error associated with it and so does the body. Your body may naturally front focus slightly and your sigma lenses may also slightly front focus and make the situation worse (or maybe they focus correctly, but your body front focuses a lot and you need lenses that have a rear focus tendency to compensate).
     
  3. finnschi thread starter macrumors 6502

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    #3
    yea But sending all this stuff to canon/sigma will cost me lots of $$$ and since i am in the market for a new Camera body anyway.... I might just buy the 50D/7D :)

    thx anyways
     
  4. John.B macrumors 601

    John.B

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    #4
    That's what the guy at the camera store wants you to think, anyway.

    (Which doesn't mean it's not the right answer for you. :))
     
  5. finnschi thread starter macrumors 6502

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    #5
    hehe yea but seriously canon Quoted me sooo much $$ for Adjustments... :rolleyes: and Since i am buying new Lenses all the time :p its better to buy a camera with those adjustments build in imho
     
  6. toxic macrumors 68000

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    Nov 9, 2008
    #6
    no, you do not. any lens can be calibrated by itself. Sigma just needs to know what camera you are using. if the lens comes back and still doesn't work properly, then you can consider mailing in your camera with it, or they will ask you to, but most of the time there is no need.

    if there is enough error in both the lens and camera to create a focusing issue, then one or both are out of calibration.
     
  7. SLC Flyfishing Suspended

    SLC Flyfishing

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    #7
    If you're in the market for a new body, and you're really constantly buying lenses, just buy a Nikon D300 and lenses and forget about having to adjust your stuff, nikon knows how to get it right the first time :p


    Just kidding of course!
     
  8. ChrisA macrumors G4

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    #8
    Actually that is true. The Nikon system is different. Niokon never changed the lens mount when they went to autofocus. You can still use old manual lenses on the D300 body. In the Nikon system the body does not tell the lens were to move to but only "move back" or "move forward". Because of this there can be no issue witha defective lens. There is never anything in the lens to get out of adjustment. If the camera sees a blur it moves the lens until it is sharp. You can see this your self in a Nikon camera with a manual lens attached. There will be little arrows that tell you which way to move the focus ring. This are the same signals that would have been sent to the lens or the in-body focus motor. It's a different design
     
  9. SLC Flyfishing Suspended

    SLC Flyfishing

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    #9
    Then why the ability to microadjust for your lens collection?

    My D700 has the capacity to save custom body focus adjustments for almost anybody's entire lens collection (I think it's 20 lens profile's that can be created and saved in camera). You are basically telling the body to compensate for front or backfocusing characteristics.

    Maybe I just don't understand the system well enough.
     
  10. AlaskaMoose macrumors 65816

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    #10
    Sigma lenses can be spot on, or not. Some of these lenses back-focus, while others front-focus. All you have to do is to figure how to check the lens focus (you can download and print some of the charts floating on the Internet to check lens focus). Once that's done, send the lens to Sigma and explain what the problem is. Sigma always takes care of the problem, and you don't have to send your camera with the lens, because the camera is not the problem.

    While the 40D does dos not have lens micro adjustment, the 50D does.
     
  11. AlaskaMoose macrumors 65816

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    #11
    What Canon changed was the mount. All bodies (Canon and Nikon control the lens forward/rearward movement). While Nikon left their mounts alone, Canon created a new mount for its cameras. A lot of Sigma lenses back or front focus, and this happens when mounted on a Canon or a Nikon camera.
    http://en.wikipedia.org/wiki/Autofocus
     
  12. finnschi thread starter macrumors 6502

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    #12
    Any experience with that procedure? some people say they had to send in the lens 3 times ... how annoying

    My Sigma 24mm 1.8 has a VERY bad front focus Problem, ie: Shooting a Portrait and later finding out that instead of sharp eyes I have a sharp nose :(
     
  13. finnschi thread starter macrumors 6502

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    #14
  14. flosseR macrumors 6502a

    flosseR

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    #15
    yea i noticed that AFTER pushing submit..... had to find an external one for my MBP.... damned...
     
  15. finnschi thread starter macrumors 6502

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    #16
    That sucks I just spilled beer on my old Powermac Keyboard (the heavy white one... now I have to buy one of those aluminium things.. :mad:
     
  16. AlaskaMoose macrumors 65816

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    #17
    As far as I understand it, Sigma corrects the problem under the lens warranty. However, if the lens is brand new, I would just ship it right away to the shop I bought it from for an exchange. Now, if you have a camera that back/from focuses with more than one lens, then there is the possibility that the camera is causing the problem. In this case you may want to send both the camera and the lenses for calibration. I would not send the camera and one lens for calibration, because it's possible that while the lens I send in is now calibrated, the other lenses won't.

    That's where the lens micro adjustment in some Canon cameras becomes useful, since you can match all the lenses to the body. But again, it's well known that some Sigma lenses may front/back focus, and that's why it's best to test the lens carefully following the instructions, and then send the photos and the lens for calibration. More than likely you won't have to send it in more than once if you test the lens in accordance to the instructions. As with any tests, one would have to use a rock-solid tripod, set the lens to the right aperture, focus point, distance from the center of the lens to the center of the chart, correct angle between lens and chart, lens on AF for a couple of photos, and then a couple of photos with lens focused manually.

    This chart was designed for Nikon lenses, I believe, but it can be used for any lens:
    http://www.dphotojournal.com/download-free-focus-test-chart/
     
  17. finnschi thread starter macrumors 6502

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    #18
    I bought the Lens in Dubai ... :cool: much cheaper but i got a international warranty card (I also bought from a REAL store, not some Street Dealer...)
    :D

    I Think I'll send the lens to Sigma thx
     

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