Reichman on EVF's and the future of optical viewfinders

Discussion in 'Digital Photography' started by RichA, Feb 17, 2011.

  1. RichA

    RichA Guest

    http://www.luminous-landscape.com/reviews/cameras/panasonic_gh2_revisited.shtml

    The Viewfinder (Panasonic GH2)

    Potentially the most controversial aspect of the GH2 is its electronic
    viewfinder. The way that MFT cameras with viewfinders achieve their
    small size is by substituting the usual mirror box and prism assembly
    for an electronic viewfinder – essentially a small video screen
    similar to what one finds on a video camera.

    Digicam EVFs tend not to be of very high resolution or brightness, but
    the one on the GH2 (and the GH1 originally) is very good indeed. In
    fact, I would say that it is an many instances preferable to the
    dismal (meant literally) and small optical viewfinders found on the
    smaller and usually inexpensive DSLRs.

    The EVF on the Sony A55 is also very good (though I haven't had a
    chance to do a side-by-side comparison), and similarly I would prefer
    these any day to a small and dim optical reflex system, especially
    those on cheaper systems that use pentamirrors instead of true prisms.

    No – these EVFs are not as bright and clear as a good bright reflex
    system, especially one on a full-frame body. But, the trade-off in
    size and weight is considerable. Also, the ability to have display
    overlays, such as a live histogram, goes a long way to making this new
    alternative viewing system attractive.

    Frankly, the writing is on the wall. It won't be more than a few years
    until the vast majority of new camera model with viewfinders dispense
    with prisms and mirrors and replace them with EVFs.

    Get used to it. It's not that we as photographers are necessarily
    asking for this (though EVF display technology is getting better all
    the time). It's just the pressure of industry economics. Price
    competition is fierce. Moving mirror assemblies and glass prisms are
    expensive to manufacture and assemble. High quality EVFs are not
    exactly inexpensive at the moment, but as with all high volume silicon
    based products, prices will inevitably fall. When that happens mirrors
    and prisms will be relegated to only the high end, where users are
    willing to pay for special capabilities.

    About 90% of the time I am not displeased using the GH2's EVF. It's
    even possible to forget that there's anything different going on. But
    in low light things get a bit weird. With a fast lens (like the
    remarkable Nokton f/0.95) the view actually becomes brighter than
    reality and the final result not what one expects.
     
    RichA, Feb 17, 2011
    #1
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  2. RichA

    Ofnuts Guest

    So the viewfinder luminosity is a matter of mirrors
    So the viewfinder luminosity is a matter of lenses

    Which one is true? Could it be that the entry level DSLR are always
    tested with their not-so-fast kit lenses?

    And is there any measure anywhere of the actual difference between
    pentamirrors and pentaprisms?
     
    Ofnuts, Feb 17, 2011
    #2
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  3. RichA

    Paul J Gans Guest

    There is a very slight light loss each time the light goes from
    air to glass and glass to air. Mirrors have at least six such
    transitions. A pentaprism has only two.

    That said, the loss is VERY small and I doubt it is detectable.
     
    Paul J Gans, Feb 18, 2011
    #3
  4. RichA

    Me Guest

    These mirrors don't have a glass/air transition, as the glass is
    "silvered" on the reflective side. Light loss is probably significant.
    How do you come up with six transitions for pentamirror?
    I count 3 - from one side to the other side of the angled roof of mirror
    assembly, to front mirror.

    I'm not sure that modern pro DSLRs with high eyepoint and focus screens
    optimised for AF systems and "100% VF" are as "accurate" as some wishful
    thinkers may like to believe. Put such a camera on a tripod, look
    through the VF at the edge of the image and move your head from side to
    side to see what I mean. An EVF would actually be better.
     
    Me, Feb 18, 2011
    #4
  5. RichA

    RichA Guest

    Odd thing is, mirror systems can be superior to prism systems and are,
    in different realms than cameras. Prisms induce chromatic aberration
    (something mirrors don't do) and absorb more light than the newest
    reflective surfaces of mirrors.
     
    RichA, Feb 18, 2011
    #5
  6. RichA

    PeterN Guest

    Another question you will evade:
    Which camera prism system are you spouting about?
    Where is the scientific backup for your statement?
     
    PeterN, Feb 18, 2011
    #6
  7. True. But it can only amplify what the sensor delivers,
    and delivers quickly (can't expose for, say, a modest 1/15s,
    or you'll have lots of fun following the action) while the eye
    has all the evolution behind it to cope with the dark at night.
    Including longer integration times without impeding following
    the action. (Or rather, if your eye cannot follow the action
    any more, you cannot blame the camera.)

    And of course you loose resolution due to the rather limited
    number of subpixels in an EVF.

    -Wolfgang
     
    Wolfgang Weisselberg, Feb 18, 2011
    #7
  8. RichA

    Me Guest

    FWIW, visible spectrum light loss from front "silvered" mirrors seems to
    be quoted (google for sources) as being in the range from 5-12%, (X3, as
    it's reflected 3 times).
    They use prisms in periscopes and binoculars etc for the same reason,
    there are much lower light losses through internal reflection in a prism
    than with mirrors.
     
    Me, Feb 18, 2011
    #8
  9. RichA

    PeterN Guest


    The mirror and prism are part of the viewfinder. The exposure plane in
    both SLRs and DSLRs is from the lens to the medium. (Either sensor or
    film.)



    Peter
     
    PeterN, Feb 18, 2011
    #9
  10. RichA

    Ofnuts Guest

    To put that in photographic perspective .88**3 is .68 (roughly
    1/sqrt(2)) so that's half a diaphragm stop. To emulate that, set your
    lens at max opening minus half a stop, and depress the DOF check button.
     
    Ofnuts, Feb 18, 2011
    #10
  11. RichA

    Me Guest

    Except it might not work like that...
    With an f1.4 lens, there's no visible difference in DOF preview VF
    brightness unless stopped down to f2.8 or smaller. The reason for that
    has been posted here before, but I've forgotten it. The maximum
    brightness (on Nikon anyway) seems to be just below f2.8.
     
    Me, Feb 19, 2011
    #11
  12. Prisms don't cause chromatic aberration if the light enters and exits
    them at near vertical to the glass-air surface transition.
     
    Chris Malcolm, Feb 19, 2011
    #12
  13. Resolutions of EVFs are going to increase in the future and for manual
    But according to Rich, if you need magnification you are blind.

    David
     
    David J Taylor, Feb 19, 2011
    #13
  14. RichA

    John A. Guest

    Seems to me that would be best done with the rear display. If you're
    being that meticulous with manual focus, and peeping that closely
    while you do it, you're probably using a tripod and probably want to
    have the camera as still as possible so you can actually see how
    focused the image is.
     
    John A., Feb 19, 2011
    #14
  15. RichA

    Ofnuts Guest

    If you do that you want to remotely control the AF because with long
    focal length touching the camera for focus is enough to blur the image
    (unless you have a rock-steady tripod). Then the focus is better
    appreciated on the display of the remote controller (PC).
     
    Ofnuts, Feb 19, 2011
    #15
  16. RichA

    PeterN Guest

    True. that is why most long lenses are mounted on the tripod.
    You get better balance.
     
    PeterN, Feb 19, 2011
    #16
  17. RichA

    Ray Fischer Guest

    Probably eventually, but they're a long way from being very good.
    Right now you can either have a big display with many pixels (but
    still only about a million), or you can have a small display with low
    resolution.

    EVFs need small displays in order to fit within the camera.
     
    Ray Fischer, Feb 19, 2011
    #17
  18. Of course. And one day we'll have flying cars that do 250 miles
    per gallon. And EVFs won't need significant power then, as we'll
    all use tiny fuel cells to drive cameras for 10 years ofvheavy
    duty use without a recharge --- and have the memory cards to
    record these 10 years in uncompressed, RAW 40+ MPIX movies.

    Just now EVFs aren't there yet, and I cannot buy and use a camera
    from the future today.
    .... it just takes several button presses ...
    If the *camera* chooses so, you meant.
    Or can you add that to a camera that misses that feature?
    And in theory everything is fine.

    And because you can enlarge, there is no need to increase the
    resolution.

    Of course, with OVFs you can use loupes and even focussing aids
    in the focussing screen. Which flatten the playing field. And,
    worse, you can switch to the monitor on the rear, which you can
    also zoom --- and there goes your EVF advantage completely.

    And of course, now you'll scream "sunlight". Which is easily
    countered by e.g. transflexive monitors. Or OVFs with EVF
    overlays, as we'll have before EVFs pick up significantly more
    resolution --- there are already DSLRs that overlay your OVF with
    additional information.

    In the end, for non-compact (and no compromises) cameras with
    viewfinders, EVF only will not happen, because choice is important
    and EVF won't be able to completely replace OVF in my lifetime.

    -Wolfgang

    PS: When will they bring an EVF that correctly adjusts to all
    brightnesses witnessed on this planet, from the glaring sun
    on the ocean or over snowfields to the darkest caves? I don't
    want to become nightblind looking into an EVF (and don't want
    to use it as a beacon or torch) and I don't want it dark(ish)
    when used in very bright circumstances. And I don't want it's
    (and the sensor's) limited range when merely observing ---
    if there's deep shadow and bright sunlight, I can see in both
    in an OVF, I don't need to decide which to watch.

    OVF isn't perfect, but much closer to the ideal viewfinder.
     
    Wolfgang Weisselberg, Feb 20, 2011
    #18
  19. And how do you manually focus pixel perfect, when your pixel
    view completely blurs whenever you even breathe on the
    camera, not to mention touch it to change the focus?

    -Wolfgang
     
    Wolfgang Weisselberg, Feb 20, 2011
    #19
  20. RichA

    John A. Guest

    Via iterations of the part you deleted from his post, obviously.
     
    John A., Feb 20, 2011
    #20
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