sensor to flange distance

Discussion in 'Digital SLR' started by Paul Furman, Feb 15, 2008.

  1. Paul Furman

    Paul Furman Guest

    Would it be worthwhile to design a new APS DSLR with a smaller
    sensor-to-flange distance? There are problems with oblique angles on
    sensors so maybe it's a dumb idea but maybe a way to have smaller or
    cheaper lenses?

    AFAIK everyone uses the old full frame distance, right? They could just
    design the lens to stick into the body further assuming the mirror is
    already smaller & there is more room. The only problem there is if you
    put that on a full frame body the mirror would get smashed.

    It *ought* to be possible to lock up the mirror with the new live view
    DSLRs but I'll bet they don't have that function, they should though,
    there's some old fisheyes which need this snd very few old film bodies
    can mount it safely. Plus there's rangefinder lenses that could be used.
     
    Paul Furman, Feb 15, 2008
    #1
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  2. Congratulations! You've reinvented the wheel. Or in this case, the EF-S lens
    mount.

    Funny that Canon is the one to have done this, since they're already the
    ones with the shortest flange to film distance. (Which, by the way, is 44mm
    or so. Which means that oblique angles really aren't a problem, even on FF.)

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Feb 15, 2008
    #2
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  3. Paul Furman

    JimKramer Guest

    You need to forgive him, he's a Nikon shooter. :)
     
    JimKramer, Feb 15, 2008
    #3
  4. Paul Furman

    Guest Guest

    olympus 4/3 has the shortest flange distance, but the lenses (and the
    cameras) aren't much smaller or cheaper. also, the oblique angle bit
    is mostly olympus marketing and not as big of an issue as it's made out
    to be.
    canon ef-s protrudes back a little further, so canon made a minor
    change to the mount to prevent putting ef-s lenses on a standard ef
    mount.
    there are two problems. the first is that it is restricted to full
    frame dslrs. on crop sensor dslrs (except for some of the early ones),
    the mirror box is smaller, therefore preventing the old lenses from
    even fitting when the mirror is up.

    the second issue is you need to be sure that the mirror doesn't flap
    back down, or if it does, it won't harm either the lens or the camera.
    with live view, you'd need a mode that doesn't drop the mirror prior to
    taking a photo.
     
    Guest, Feb 15, 2008
    #4
  5. Paul Furman

    Paul Furman Guest

    Ah, OK thanks all. Are other brands the same?
    That could be bigger easily. I'm also wondering about rangefinder lenses
    on a full frame DSLR.
    I understand the mirror needs electricity to hold it open so a use a
    clip in the mirror box to hold it. Could you put rangefinder lenses
    inside that? I'm guessing the mirror box needs to be bigger yet, maybe
    even the mirror retracted further to the side, or would it work?
     
    Paul Furman, Feb 15, 2008
    #5
  6. Paul Furman

    Guest Guest

    nope, only canon did that. with nikon (and i'm pretty sure with pentax
    and sony), you can mix and match lenses. interestingly, third party
    canon ef-s lenses have the standard ef mount and will fit on canon full
    frame cameras, probably because they're designed to use the normal
    flange distance for the nikon, pentax and sony mounts.
    i'm not entirely sure clipping the mirror up is a good idea, but i've
    never tried it. let us know how it works out. :)
     
    Guest, Feb 15, 2008
    #6
  7. Paul Furman

    Doug Jewell Guest

    Yep, Pentax & Sony, in addition to Nikon use the same mount.
    Nikon's D3 allows you to use DX (ie smaller image circle)
    lenses even though it is a full-frame camera - it simply
    crops to the smaller area. I have quite successfully used a
    Pentax 18-55 DA lens on a film camera - it vignettes badly
    at 18mm, but by 24mm you have full frame coverage.

    Because of the longer flange distance, by necessity the
    lenses are retro-focus designs and hence the light is
    hitting the sensor at an angle fairly close to
    perpendicular, which is optimal for digital sensors.
     
    Doug Jewell, Feb 15, 2008
    #7
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