Microprisms...

Discussion in 'Photography Beginners' Forum' started by eight08, Mar 28, 2010.

  1. eight08

    eight08 TPF Noob!

    Joined:
    Mar 28, 2010
    Messages:
    4
    Likes Received:
    0
    Hey guys! I have a Yashica 109MP, it has a microprism focusing thingy... and just wondering, sometimes, when focusing, one of the sections goes black... why is that? and how would it affect the shot?
     
  2. KmH

    KmH Helping photographers learn to fish Supporting Member

    Joined:
    Apr 9, 2009
    Messages:
    38,240
    Likes Received:
    5,009
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    Sounds like something worth looking up in that little book kinda thingy that comes with most cameras.
     
  3. Derrel

    Derrel Mr. Rain Cloud

    Joined:
    Jul 23, 2009
    Messages:
    35,456
    Likes Received:
    12,797
    Location:
    USA
    Can others edit my Photos:
    Photos OK to edit
    Sounds like you might mean a split-image rangefinder focusing 'thingy', which will go black when the maximum aperture of the lens or lens+ extension tube or lens+ teleconverter drops below roughly f/5.6 or so. It's called "rangefinder black-out" and is/was pretty common with "slow" lenses.

    The split-image rangefinder in the center of the viewfinder screen was often surrounded by a microprism circle, often called the microprism doughnut.
     
  4. eight08

    eight08 TPF Noob!

    Joined:
    Mar 28, 2010
    Messages:
    4
    Likes Received:
    0

    Thanks for the reply... i was just wondering, would it affect the shot at any way?
     
  5. eight08

    eight08 TPF Noob!

    Joined:
    Mar 28, 2010
    Messages:
    4
    Likes Received:
    0
    It's not in there...
     
  6. Dwig

    Dwig TPF Noob!

    Joined:
    Mar 11, 2009
    Messages:
    1,261
    Likes Received:
    0
    Location:
    Key West FL
    Can others edit my Photos:
    Photos NOT OK to edit
    Actually, one of the facets in a "split rangefinder prism" or a "microprism array" can black out at wider apertures. When this is happening the cause is that your eye is not well centered in the VF. The blackout Derrel is refering to occurs when the lens' maximum aperture is so slow that no matter where you place your eye one of the RF's prisms is black/dark. When this happens with microprisms, only one or two of the six facets on each of the hundreds of little prisms blacks out. Focusing is not practical, but the dark areas are small and less annoying.
     

Share This Page