is my lens crappy or is it me?

Discussion in 'Beyond the Basics' started by kkamin, Nov 24, 2009.

  1. kkamin

    kkamin TPF Noob!

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    Hello,

    I'm shooting with a Canon xsi with the standard 18-55mm EF-S lens that frequently comes with it. I've been shooting with strobes at 1/125th at F/8, 200 ISO. The problem is that some of my shots are not very sharp.

    The strobe is firing very fast (I think somewhere between 1/800th sec to 1/2000th sec). There is almost no ambient light in the studio. SHouldn't the strobe freeze the action, almost no matter what?

    Could it be the lens itself does not have the best optics? How much improvement would I notice if I went to a 70mm prime? Is there anything decent I can buy for $200?

    Thanks, everyone.

    Kkamin
     
    Last edited: Nov 26, 2009
  2. Derrel

    Derrel Mr. Rain Cloud

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    I have the Canon EF 18-55 kit zoom, the non-IS one, the early USA version, not the Japan-market one with the ultrasonic motor. The lens performs absolutely craptastically--lots of color fringing, bad edge performance, just an all-around subpar lens design. Very weak optical performance,even fairly well stopped-down. Apparently, the later, Image Stabilizer version is a better lens.

    70mm brings to mind the Sigma 70mm macro lens, which is a really good lens from everything I've seen shot by it. It would be easy to find a cheap,modern zoom lens that would perform better than the first-version 18-55.
     
  3. grafxman

    grafxman TPF Supporters Supporting Member

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    A prime will usually have better optics than a zoom. Before you go purchase another lens perhaps you should check your lens' sharpness using the technique described here:

    AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2, 7D

    That procedure will tell you about your lens' sharpness as well as how to correct an out of focus condition.

    Alternatively you could tape up a newspaper page 15 feet or so away, mount the camera on a tripod, manually focus using a magnified live view, then switch to automatic focus, press the shutter release and see if the focus ring moves. The lens should be wide open using this procedure so there is no depth of field. If the focus ring moves, you MAY have a problem that you need to correct with a camera adjustment. Try the procedure at various zoom settings. Hope this helps. Good luck.
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Unfortunately, the XSi doesn't have micro focus adjust. (not that I know of, anyway).
    You can still do some fairly simple tests to check the focus accuracy.

    It would help if you could post up some examples. It may or may not be a 'poor lens' issue...and it may or may not be a focus issue.

    I've also got the old 'crappy' 18-55mm lens. It's not as bad as most people make it out to be...but I haven't used mine in several years because I have better lenses in my bag.

    The EF 50mm F1.8 is Canon's least expensive lens. It's 'cheap' and has many plastic parts...but the glass is pretty decent.
     
  5. Village Idiot

    Village Idiot No longer a newbie, moving up!

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  6. IgsEMT

    IgsEMT No longer a newbie, moving up!

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    Look into used equipment from reliable dealer. My main glass in used, no VR but its quality is AMAZING (and I'm being objective here). :)
     
  7. Derrel

    Derrel Mr. Rain Cloud

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  8. ZBob

    ZBob TPF Noob!

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    It's crappy. Try the 50mm 1.8 II. It's really cheap and very sharp.
     
  9. cfusionpm

    cfusionpm TPF Noob!

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    That's cool and all, but that's not the lens the OP has. This is: http://the-digital-picture.com/Reviews/Canon-EF-S-18-55mm-f-3.5-5.6-IS-Lens-Review.aspx

    Though, he does have some nice things to say about the "L-class image quality" 17-55mm 2.8 lens. :)
     
    Last edited: Nov 25, 2009
  10. kkamin

    kkamin TPF Noob!

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    Here is the image. It looks fairly sharp at 100% magnification (cropped down to about seventy percent of its original size), but when I zoom in, all the girl's faces are like the one I isolated. Maybe I am expecting too much from the lens, but I would think it would be sharper than that. (The close up of girl's face is at 100% magnification, it hasn't been resized).

    And again, I am shooting with strobes and my camera is at a 1/200th sec. , ISO 200, f/8

    [​IMG]
     
  11. Derrel

    Derrel Mr. Rain Cloud

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    Yup, that's what a crummy optical performance looks like. She's in focus--this is not a case of mis-focusing or being outside the depth of field band. That's just bad optics. And what a shame too--the photo is simple and well-lighted. One would expect that at f/8 a lens would be good. Your work deserves better.
     
  12. grafxman

    grafxman TPF Supporters Supporting Member

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    You're probably right. F8 should have everything in focus. However, to my old eyes, that collar area looks razor sharp to me. I zoomed in to 200% with my Opera browser and it still looks sharp.

    I reiterate what I stated in a previous post, the lens should be opened wide with the camera on a tripod. It should be manually focused onto a newspaper mounted 15 feet or so away using the magnified life view. It should then be placed to auto focus and the shutter release pressed while watching the focus ring. If it moves then you have a focus problem, not necessarily a bad lens. The focus problem may possibly be corrected within the camera or by sending it to Canon. It's a simple test that can be easily accomplished within 30 minutes or less.
     

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