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Thread: Lens focusing

  1. #1
    Junior Member
    Join Date
    Sep 2010

    Thumbs down Lens focusing

    I own a Vivitar 3800N and a K-1000. I noticed that on distance subjects, the Vivitar will not give me a sharp image using its own lens OR the K-1000 50mm lens.

    One person told me that there is a problem with the vivitar's shutter.

    Anyone know what causes this?

  2. #2
    Pentax Forum Moderator
    Join Date
    May 2005
    Platteville, WI, United States

    Re: Lens focusing

    Hi John...Welcome to PR and the Pentax Forum. I'm sorry I don't have an answer for you. However, If we don't get something from someone on this forum shortly, I'll move this thread over to the help forum and maybe we can get you an answer over there. I will also look around and see if I can find an answer for you.

    In the meantime, please post a couple of examples. Sometimes what seems to be focus issues may be motion blur issues. Are you using a tripod when you shoot long distance? What settings are you using?

    Again, welcome and I look forward to seeing some of your photography.

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  3. #3
    Junior Member
    Join Date
    Sep 2010

    Re: Lens focusing

    This photo was taken using a Vivitar 3800N Camera and 50mm lens.
    The film was Kodak E-6 film extra color 100.
    Photographed at IS0 100, lens set at between 5.6 and 8 @ 250

    You will notice that it looks pretty good small, but when you enlarge the photo, it has no sharpness. I should point out that this slide was scanned on a Epson V500 scanner using different settings including professional mode @ 600 dpi and 1200 dpt and the results were pretty much the same. I even took the film out of the cardboard mount and scanned it against the glass hoping to improve the sharpness which it had only a small effect.

    I also used a Pentax SMC 50mm lens on the same camera and received similar results.

    I have drawn the conclusion that there is something wrong with the camera. Any thoughts?
    Attached Thumbnails Attached Thumbnails Lens focusing-wntp-4228-.jpg  

  4. #4
    Senior Member freygr's Avatar
    Join Date
    Feb 2005
    Portland, OR, USA

    Re: Lens focusing

    There are many factors as per sharpness.
    1) Film type, ISO higher = more grain, less sharpness
    2) DOF
    3) shutter speed, slow = more chance of movement during exposure = less sharpness
    4) Camera movement during exposure

    You need to use a tripod and take a few test shots.

    A note, scanned image is to low of a resolution to say that it is not sharp.

    Panorama Madness:

    Nikon D800, 50mm F1.4D AF, 16-35mm, 28-200mm & 70-300mm

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