Help, -2 diopter on my Hasselblad, can this affect focus? Help with identifyng split screen.

Discussion in 'Medium Format' started by mati, Sep 9, 2020.

  1. Hello there,

    I had my Hasselblad 500 cm for a while and it seems my focus is not always reliable. At times I have it, other times I miss it. I am not sure if it is a matter of me moving the camera or if I am just missing the focus. I just noticed I have a -2 written next to the diopter. Could this affect focus? Also, I am not sure which kind of split-screen I have. Attached photograph.

    [​IMG]

    Would you say that changing the diopter and the screen could improve my situation? I know that there are also prisms, but I am really new at this and just always used what it came with my Hasselblad. I know many people suggest ACUTE Matte D, but it would be great starting with identifying my screen!

    Thank you so much!
     
  2. That looks like a 42188 split screen pre Acute Matte, but could also be an aftermarket. They never made an Acute Matte with split screen only (at least I've never seen one listed).

    Are your images consistently front or back focused? I have an aftermarket Brightscreen that consistently back focuses (ie: not in spec).

    -2 diopter is typically for people that are slightly near sighted. Can you see the marks on the screen (ie: the edge of the split image semi circles) clearly. Try pushing the magnifier in slightly to see if the screen becomes clearer. Depending on your eye sight, you might be better off with a different diopter. "0" or neutral diopter was stock, and placed the screen to appear at infinity. -1 diopter placed the screen at 1m. I'm slightly near sighted, so I use a -1.
     
    Last edited: Sep 9, 2020
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  3. The purpose of a diopter eyepiece is so you can focus on the screen, that is, the focal plane of the screen. Grid markings, if any, are in the correct focal plane. The Fresnel lines are a little above the plane, and any marks on the top of the screen are useless in this regard. That done, you can concentrate on focusing the image.

    Most ground glass screens are more transparent than necessary in order to provide a brighter image. You are able to look through the screen and focus on a virtual image behind it, resulting in far-focus errors. It's easy to do because your eye is more comfortable when it is more relaxed.

    The "best" focusing tool is probably a chimney finder. The magnification is high and the eyepiece can be accurately focused on the screen when your eye is most comfortable.

    Concentrate on the screen while focusing, and you can expect better results.
     
  4. SCL

    SCL

    I've found on my SLR medium format cameras (never had a Hassy though) that having the correct diopter in place I was able to nail focus quite easily in spite of wearing glasses. I'd check the original specs to see what diopter was installed, and if your eyesight is normal, ie you can properly focus both near and far, that you install that diopter. An alternative is to take your camera to a dealer and try various diopters until you get one that works for you. Or if Hasselblad has a viewer with a variable diopter viewfinder, as my Bronica did, you might consider switching to it, and then as your eyes age minor adjustments are quite simple to continue your enjoyment with the camera.
     
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