Discussion in 'Lens Lust' started by sarhento, Aug 14, 2005.

  1. Hi Everyone,

    when you acquire a lens - new or used, do you always subject it through some testings to see if it meets your standard? If so, would you mind sharing your setup and procedure?

    I would like to learn from you something I can use on my current collections as well as future acquisition.

    Thank you in advance.
  2. Hi Sarhento,

    Most of my recent lens acquisitions have been of the used variety, so I probably give them a closer look than I would when buying new.

    Things I generally check for on a used lens are marks or scratches on the front and rear glass, fungus on the glass, oil on aperture blades, stickiness of aperture blades, dust inside the lens, mechanical smoothness/holding of focus and zoom rings, and functioning threads on the filter ring.

    I then take tripod-mounted, remote release shots of a focus target with each of my camera bodies at every focal length/aperture combination. Here is my obviously home-made focus target of newsprint taped to staggered cassette boxes. ( D2H, 28-70, f/2.8 at 70mm)

    My tests are primarily to check for back focus/front focus and general sharpness. I am less concerned with corner softness, but that's just me.
    My test is far from scientific, but is enough to satisfy my level of concern and ease my anxiety.

    I'd be interested to hear what other folks do.

  3. Glenn,

    What's the distance between your camera and the test target? Is it the same at different focal length? Why did you choose that distance as opposed to others?

    Oh, haved you returned any lens based on this test?

    thanks for sharing.
  4. Sarhento,

    I generally try to shoot my tests at slightly beyond the minimum focus distance for the given lens. I find that if I increase the camera-focus target distance too much, then it's harder for me to judge the focus quality.

    No, I've been fortunate and have never had to try and return a lens. My first D70 had a backfocus problem that Nikon cured.

  5. Glenn,

    I am looking forward to testing and comparing my 28-70 lenses - nikon and tokina using your setup and method. This is just to satisfy my curiosity.

    Lately, I noticed that my nikkor 28-70 is soft on the left side of the image when wide open. Do you have this lens and do you find it to be so?
  6. Sarhento,

    No, I haven't noticed any left-side softness on my Nikon 28-70.

    To test for that problem on your Nikon 28-70, you could just tape a full newspaper sheet to a flat surface like a wall. Any softness on one side or the other should be revealed by discrepancies in the clarity of the newsprint.

  7. One more question, Glenn.

    How do you test for back/front focusing?
  8. Sarhento,

    By staggering the newsprint-covered cassette boxes at different depths, and focusing on a box at a middle depth, you can determine by clarity of the newsprint whether there is back/front focusing. I stagger them by the depth of each cassette box.

    Hope this helps.

  9. thanks again, Glenn.

    I should have re-read your previous posts before asking the back/front focus testing :oops:
  10. No problem, Sarhento.

    I just hope your lens is functioning as it should be.

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