Why no LCD screen preview on DSLRs?

Discussion in 'Digital SLR' started by squirrelmaster, Mar 8, 2006.

  1. Maybe this is a dumb question, maybe not, but here goes..

    Why don't digital SLRs allow previewing using the LCD screen? It would
    seem that to do this, the mirror would have to be temporarily
    locked-up, and the image sensor enabled. This is what point-and-shoot
    digital cameras do, except that there's no mirror.

    My guess is that this is counter to how SLRs have always been used.

    In fact, one could build a DSLR camera without the mirror and just rely
    on the LCD screen for the viewfinder. Of course the "R" in DSLR would
    have to be dropped as there's no mirror. Okay, a viewfinder-less camera
    wouldn't be that great, but I don't see why manufactures don't
    implement a LCD preview feature. This would also eliminate mirror flip
    related shake during bulb exposures.

    squirrelmaster, Mar 8, 2006
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  2. squirrelmaster

    Paul Furman Guest

    There is a new one coming out with that from oly or panasonic I think.
    It's supposed to compromise the viewfinder some and is being done on a
    4/3 sensor which is somewhat smaller. Basically I think it's a matter of
    larger sensors costing more so they optimise for single capture instead
    of spending on video capture ability, the one coming out has a second
    sensor (I think??) that picks up a reflection off the mirror or
    something like that.
    Paul Furman, Mar 8, 2006
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  3. squirrelmaster

    Jeremy Nixon Guest

    The sensors normally used in SLRs are not capable of live preview.
    Adding that capability compromises image quality, because some part of
    the sensor needs to be occupied by the circuitry to do the preview
    instead of being occupied by stuff to create the actual image.
    Jeremy Nixon, Mar 8, 2006
  4. squirrelmaster

    Tony Polson Guest

    The new Olympus E-330 does. So will the first digital SLR from
    Panasonic, which is based on the E-330.
    Tony Polson, Mar 9, 2006
  5. squirrelmaster

    Sheldon Guest

    If you think about it, make a DSLR the way you would like and it would work
    like a Hassleblad. It would have to be open to preview the image, then shut
    down and reopen to capture the image. Talk about slow.
    Sheldon, Mar 9, 2006
  6. squirrelmaster

    BobFlint Guest

    There are lots of reasons, one being that the real view through the glass is far
    superior to any electronic viewer, (the reason I junked my Dimage and bought a
    D70), and also the power required by the full time use of the sensor would
    negate the long life of the batteries, which I charge every 700 pics, as opposed
    to every 75 pics with a P&S.

    Note that some new cameras do offer full time preview, I think with a different
    sensor then the main.

    As far as I'm concerned, I've used all types, including "viewfinder film"
    cameras, and I don't care for any electronic display.

    Maybe in the future we'll have twin lens cameras, one for electronic view and
    one for taking the pic, like a 2&1/4 or something...

    Damn I wish my D70 had the split screen view of my Minolta X-9!
    BobFlint, Mar 9, 2006
  7. It's tard time again.
    Randall Ainsworth, Mar 9, 2006
  8. Yeah, you had to come in with your pointless, worthless comment,
    insulting someone who doesn't have as much knowledge as you do.

    Tard time, no kidding.
    mike.hamilton, Mar 9, 2006
  9. squirrelmaster

    Frank ess Guest

    You know, Mike the only time many of us are subjected to Radall'
    predictable spew is when someone "has to come in" and answer him.

    Frank ess
    "One time, I got up the next morning and looked in the mirror
    and there were two of them up in my hair."
    - JEAN LEMEAUX, on the travails of removing those little stickers from
    fruits and vegetables.
    Frank ess, Mar 9, 2006
  10. squirrelmaster

    Rich Guest

    They could design the camera so the mirror would swing up out of the
    way (mirror lock up?) and then they could turn on the sensor to
    provide an LCD "live" view that way. But I understand the big 1.6:1
    or larger CMOS sensors draw too much power, so the battery would
    simply die too fast.
    Rich, Mar 9, 2006
  11. squirrelmaster

    werdan Guest

    The EOS 630RT 35mm camera had a fixed mirror that was semi transparent. It had the advantage of
    being really quick to fire and no mirror shake. The disadvantage was that you lost one stop of
    available light because half of it went to the viewfinder. They could re-introduce something like

    Better still would be to just have a small section of the mirror semi-transparent and mount a second
    'compact' sized sensor in the bottom of the camera. Something like an Ixus sensor would be perfect.
    It could provide the preview iamge as well as capture video.
    werdan, Mar 9, 2006
  12. squirrelmaster

    Jeremy Nixon Guest

    I didn't say it's not possible because the mirror is in the way; it's
    not possible because the sensors don't do live preview at all. The
    only reason they don't do live preview is to maximize image quality --
    and that's a big enough reason for me to not want it, since I see
    almost no value in it as a feature.

    The other method is to use a second sensor in the viewfinder's light
    path, which that one new SLR also does; the problem with that is that
    you end up losing light for the optical viewfinder, which isn't as big
    a tradeoff as the image quality thing, but it's still significant (and
    also not worth it to me).
    Sort of like a P&S camera, then. :)
    Jeremy Nixon, Mar 9, 2006
  13. squirrelmaster

    cjcampbell Guest

    No reason to get rid of the mirror; most mirrors allow some of the
    image to pass to the light meter anyway. You would have to open the
    shutter, though, as well as enable the sensor.

    The reason DSLRs are faster than other kinds of digital cameras is that
    they have a real shutter. There is no time lag as the sensor is
    momentarily turned off and then on again. There is also no delay
    between what you see in the viewfinder and the shutter being tripped.

    An image has to be processed before it will appear on an LCD. This
    takes time and creates a noticeable delay. You can wave your hand in
    front of the lens of a camera with LCD preview and see this delay on
    the screen.

    The ON/OFF switch on a DSLR basically allows the shutter release to be
    activated, nothing more. If you leave a DSLR on the battery drains no
    faster than if you turn it off. Put an LCD in there, though, and you
    are talking about serious battery drain. People already gripe that the
    batteries don't last long enough.

    The sensors on other digital cameras have no shutter. They are on all
    the time, draining the battery, when the LCD is on. But they cannot
    take a picture in that mode. They have to shut off momentarily when the
    "shutter release" is tripped, then turn themselves on again for the
    length of the exposure, then turn themselves off and then on again in
    preview mode. All this processing delays taking the picture and again
    storing the picture in memory. A DSLR does not do that. The sensor is
    on only for the moment that the shutter is open. It does not transmit
    anything to the LCD; instead the LCD displays the photo after it has
    been processed and saved on the memory card.

    Putting LCD preview on a DSLR would negate most of the advantages of
    the DSLR, leaving you with the liabilities, such as dust on the sensor.
    cjcampbell, Mar 9, 2006
  14. squirrelmaster

    Toby Guest

    The main question is why you would want this. It is harder to focus, harder
    to see--especially in bright light, eats battery power...Why even have a
    reflex if you want to view a crappy LCD screen to focus and compose?

    Toby, Mar 9, 2006
  15. squirrelmaster

    per Guest

    It's a matter of definition what is based on what.
    The sensor is Panasonic, the mirror box they developed together, and the
    rest is different.
    per, Mar 9, 2006
  16. Look here:

    Available since march 2006.
    The E-330 implements this as mode B. The drawback is that by flipping
    the mirror away, the Af sensors can not work (because they are located
    inside of the viewfinder). Therefore, Olympus offers a Mode A for this
    camera. In Mode A, an additional CCD-Sensor inside of the viewfinder is
    used for the preview function. The drawback is that you do not get a
    100% pane of the image, it captures only 92% approximately.

    Clemens Dorda, Mar 9, 2006
  17. Yes, it is.

    A pointless feature, if you want that just buy a point and shoot.


    "A combat photographer should be able to make you see the
    color of blood in black and white"

    David Douglas Duncan
    Speaking on why in Vietnam
    he worked only in black and white
    John A. Stovall, Mar 9, 2006
  18. You're right. Why should someone educate themself?
    Randall Ainsworth, Mar 9, 2006
  19. At long last...someone who gets it.
    Randall Ainsworth, Mar 9, 2006
  20. squirrelmaster

    Kyle Jones Guest

    If you have poor vision then manual focusing may work better with a
    camera like the E-330. I haven't tried it yet so I can't say for sure,
    but previews I've read seem promising. If you have good vision you may
    find it hard to imagine but the view on a camera LCD is often an
    improvement over what I can see through an optical viewfinder. This is
    not a fluffy frilly feature to me--- it will allow me to make better

    The E-330 LCD also flips out so you can shoot with your hands above your
    head or at hip level and still compose accurately. This could be useful
    for street shooting and should be considerably more useful than
    traditional right angle finders for this purpose.

    If you've ever shot on a cold day you know that fogging of the
    viewfinder is a constant problem. Being able to compose with the camera
    held away from your face should be a win here.
    Kyle Jones, Mar 9, 2006
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