Lens Sharpness test: advice

Discussion in 'Photography Equipment & Products' started by ranmyaku, Dec 20, 2007.

  1. ranmyaku

    ranmyaku TPF Noob!

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    I have attempted to test the sharpness of my lens, although I have no special cards or fancy equipment. Can anyone give me some feedback...

    I used a 200% crop b/c it appeared at 100% i might not be able to tell much difference between the photos.

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  2. ranmyaku

    ranmyaku TPF Noob!

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    the only place I had to test was the building at my apartment directly across from me. I used a tripod and a IR shutter release. The building is probably 15 yards away or so.

    All of the crops are from the extreme far right and left of the photo in the middle.
     
  3. Big Mike

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

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    I'm not much for this type of lens testing. Just go out and shoot things that you normally would...real world testing.

    Also, normally you would compare centre sharpness to edge sharpness. The centre is almost always sharper...and on a wide lens like this, the edges usually have the most trouble. What's the point of comparing the left and right edges?
     
  4. ranmyaku

    ranmyaku TPF Noob!

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    Not sure why I chose the edges. That's why I was looking for advice. Your point is well taken though.
     
  5. Sideburns

    Sideburns TPF Noob!

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    Just shoot stuff. The noticeable difference in a real picture without cropping in to 200% is barely anything (probably nothing).
     
  6. ranmyaku

    ranmyaku TPF Noob!

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    I guess I was just wanting to know whether or not to return the lens if I got a "bad copy"

    But I guess that would be pretty evident in the photos I take if it was bad.
     
  7. Garbz

    Garbz No longer a newbie, moving up!

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    It would be hard to tell on those images. Next time photograph something with some actual detail like carpet, a leaf, sand, or side light the wall to bring out it's grain.

    To tell you the truth even my kit lens would look ok subjected to that test. Also don't forget given the shutterspeeds you're using you should use mirror lockup.
     
  8. Bobby Ironsights

    Bobby Ironsights TPF Noob!

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    Yes,

    I completely disagree with the "test on thing you normally shoot" thing.

    My Photography prof is adamant, that the best way to test a lens, is to shoot a sheet of newsprint.

    Find your flattest wall, hang your newpaper across the wall, and spray with water, or water with a pinch of cornstarch mixed in.

    That will make your newspaper stick. Then, make sure your lens is absolutely parallel to the wall. You do that by laying a meterstick across the rim of the lens, and measuring to the wall at both ends of the meterstick. The distances should almost precisely match up, if your lens is parallel to the wall. You'll need a helper.

    Then take your pictures. Blowups will have more meaning too. since newsprint is white/black, you can test for both contrast, and sharpness at the same time.

    I've got to admit, that I have yet to get around to testing my lens, but that is supposed to be how it is done. She also said the black marks come off the wall easy if you wipe with a 3% bleach solution, and ideally, you'd use a plate glass window for perfect flatness, instead of a wall.
     
  9. gryphonslair99

    gryphonslair99 Been spending a lot of time on here!

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    Bobby,
    Show this to your photography teacher and explain that this is a whole lot easier and cleaner.
    http://focustestchart.com/chart.html
     

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