Why no image playback with DSLRs ?

Discussion in 'Digital Photography' started by Alfred Molon, Mar 7, 2004.

  1. Alfred Molon

    Alfred Molon Guest

    If I'm not mistaken with a DSLR there is no visible image before taking
    the shot (as is the case with non DSLR digicams). But such a playback
    would be helpful to judge if the exposure if correct before pressing the
    button. So why isn't this feature available in DSLRs ? Since the mirror
    is semitransparent, the CCDs should receive light even with the mirror
    on.
    --

    Alfred Molon

    http://www.molon.de/Galleries.htm - Photos from Myanmar, Brunei,
    Malaysia, Thailand, Laos, Cambodia, Nepal, Egypt, Austria, Budapest and
    Portugal
     
    Alfred Molon, Mar 7, 2004
    #1
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  2. Alfred Molon

    dj_nme Guest

    My best guess is that because the fixed pellicle mirror (or
    beamsplitter) redirects a large proportion of the light into the
    viewfinder, it would limit the highest ISO possible.

    An example of a film SLR with a pellicle mirror is the Canon EOS RT,
    that reflects two thirds of the incoming light to the viewfinder and so
    only a third of the light can get to the film.

    The Olympus e-10 and e-20 are the only (that I could think of) DSLRs
    that have a beamsplitter instead of a flipping mirror.
    The both go up to (only) ISO 320, in contrast the E-1 goes all the way
    up to ISO 800 (without ISO boost) and so is almost three times more
    light sensitive that both the E-10 and E-20.

    That pretty much makes the case that the beamsplitter or pellicle mirror
    shunts too much of the light away from the sensor to make low light
    photography (without flash) realy useful.

    Just my 2 cents.
     
    dj_nme, Mar 7, 2004
    #2
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  3. Alfred Molon

    Alfred Molon Guest

    I see, but the image which the CCD sees before image capture could be
    ISO boosted. The only purpose of image playback before capture would be
    anyway to judge the exposure, whether it's correct or not (and for that
    of course a histogram would have to be displayed.
    --

    Alfred Molon

    http://www.molon.de/Galleries.htm - Photos from Myanmar, Brunei,
    Malaysia, Thailand, Laos, Cambodia, Nepal, Egypt, Austria, Budapest and
    Portugal
     
    Alfred Molon, Mar 7, 2004
    #3
  4. I have never heard about a beam splitter camera where the
    beam splitting mirror is removed at exposure. It might
    be hard to construct one, mechanically or optically.

    Moreover, the sensors used for DSLR are not suitable
    for image playback. They use the image elements as charege
    shift registers. At least the CCD cameras does. I don't know
    about the Canon CMOS thingies though.


    /Roland
     
    Roland Karlsson, Mar 7, 2004
    #4
  5. Alfred Molon

    Mark B. Guest


    The sensors used in DSLRs do not allow for live video feed.

    Mark
     
    Mark B., Mar 7, 2004
    #5
  6. Alfred Molon

    Bill Hilton Guest

    From: Alfred Molon
    Most people simply shoot and check the histogram, then adjust exposure as
    necessary. No big deal ...
     
    Bill Hilton, Mar 7, 2004
    #6
  7. Alfred Molon

    [BnH] Guest

    I read somewhere that it is DO able on a Contax N system [ or was it Olympus
    E-1 ? hmm ]
    with an extra attachment.

    =bob=
     
    [BnH], Mar 7, 2004
    #7
  8. The mirror isn't semi-transparent. It reflect all of the image, flips up out
    of the way just before the shutter fires. The fact the the mirror is 100%
    reflective and the image sensors in current dSLRs have no video capability
    (noise issues) eliminates the possibility live preview on dSLRs the way they
    are currently designed. Olympus experimented with live preview using a beam
    splitter on their E10 and E20 dSLRs. Note that they didn't go that route on
    their flagship E1.

    They're not good enough for accurate focus, their adjustable
    contrast/brightness makes accurate rendition of exposure difficult, and
    their video nature (necessary for live preview) induces unacceptable shutter
    lag, their small senors are more noise-prone. Battery issues, CCD quality,
    image noise...there are too many compromises in quality with live preview.

    Most of the people, traditionally, who have been using dSLRs are pros and
    advanced amateur photographers who could justify spending thousands on a
    camera. Those folks have come out of the film dSLR ranks and don't want live
    preview. It's far more accurate to focus and compose through a single lens
    reflex viewfinder, shoot a test shot and immediately review the histogram
    for exposure.

    HMc
     
    Howard McCollister, Mar 7, 2004
    #8
  9. Alfred Molon

    Lourens Smak Guest

    The contax N had/has? a video-viewfinder with external LCD display
    available as an option. I think it fits both the N-digital and the N1.

    Of course, a video-feed of the viewfinder image is not the same as
    checking exposure on a display with a signal from the main CCD.

    Lourens
     
    Lourens Smak, Mar 7, 2004
    #9
  10. If I'm not mistaken with a DSLR there is no visible image before taking
    Sounds like someone who needs to stick with kiddie cameras.
     
    Randall Ainsworth, Mar 7, 2004
    #10
  11. There are a lot of people out there using point-and-shoots that have really
    come to rely on an EVF or live preview for their photography. Now, as dSLRs
    get cheaper and become a viable alternative for those point-and-shooters,
    they are often put off by the fact that there are no dSLRs with live
    preview. I'm sure that lack of live preview is keeping at least a few
    newbies from moving to a dSLR.

    As dSLRs begin now to move away from the pro and advanced amateur ranks
    (that don't want EVF) to try to expand their market to the entry-level
    people, I'll bet that there is at least some R&D effort on the part of
    Nikon/Canon/Fuji to provide live preview on a dSLR. I don't imagine they're
    working very hard at it, but as a ploy to capture market share for selling
    their lenses, I bet they're working on it to some degree.

    HMc
     
    Howard McCollister, Mar 7, 2004
    #11
  12. Alfred Molon

    Bill Hilton Guest

    From: "Howard McCollister"
    Good points, and well expressed.
     
    Bill Hilton, Mar 7, 2004
    #12
  13. Alfred Molon

    Lucas Tam Guest

    True, but wouldn't live preview be another nice feature to have?
     
    Lucas Tam, Mar 7, 2004
    #13

  14. Not if the trade-offs are shutter lag, increased battery drain, or increased
    cost.

    HMc
     
    Howard McCollister, Mar 7, 2004
    #14
  15. Alfred Molon

    Lucas Tam Guest

    We're talking strictly about the feature. I doubt dSLR designers would add
    all the variables you mention just to get live preview.
     
    Lucas Tam, Mar 7, 2004
    #15
  16. Uh...no. It drives me nuts to see retards holding a digital camera at
    arm's length trying to compose a picture. Guess you might as well put
    tape over the eyepiece. How have I made it for 35+ years of doing
    photography without a preview.

    They could take the review screen off my 10D and I wouldn't miss it.
     
    Randall Ainsworth, Mar 7, 2004
    #16
  17. Alfred Molon

    Lucas Tam Guest

    You'll be surprised until you give it a try.

    I thought it was retarded until one day I tried it for a quick snapshot...
    it's much quicker than raising the camera to my eye, composing everything,
    then shooting.

    It's useful in some situations.
     
    Lucas Tam, Mar 7, 2004
    #17
  18. Not for me. I find it to be a PITA on my S400 and my 3030z. I use it
    occasionally, but only because the viewfinder sucks so bad on those two
    cameras. And photographers over the age of 45 with presbyopia (such as I)
    can't really see an EVF clearly anyway. Optical viewfinder is VASTLY
    superior IMHO, if for no other reason than the fact there is a diopter
    adjustment on the eyepiece, making it accurately useable for older
    photographers.

    HMc
     
    Howard McCollister, Mar 7, 2004
    #18
  19. Sounds only suitable for static subjects with the camera on a tripod,
    though. I think that I would miss 50% or more of my photos if I had to
    review the histogram after each shot!

    Cheers,
    David
     
    David J Taylor, Mar 7, 2004
    #19
  20. []
    Why would I want to buy extra lenses at perhaps ten times the weight and
    bulk?

    Let's move on from this obselescent 35mm is all approach!

    Cheers,
    David
     
    David J Taylor, Mar 7, 2004
    #20
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