Digital Rebel LCD focus blurry

Discussion in 'Digital SLR' started by RichardClinton, Dec 29, 2004.

  1. When I try to check for fine focus on the LCD screen, the 4x magnified image
    is a little blurry and I can't tell any difference from in and out of focus
    areas until I look on my computer monitor. Is there some adjustment to be
    made for screen focus? Thanks.
    RichardClinton, Dec 29, 2004
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  2. I've never been able to check focus with the LCD, even with zooming. It just
    doesn't work.
    Dave R knows who, Dec 30, 2004
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  3. Hang on! Are you guys talking about the EVF focus, cause I have no way of
    focusing through the LCD when taking a shot. Or am I confused as usual?
    Toomanyputters, Jan 1, 2005
  4. RichardClinton

    Colin D Guest

    Mine is too, though when I got the 17-85mm IS lens, the magnified view
    on the LCD wasn't nearly as burry as with the kit lens, though it still
    is a little.

    Colin D, Jan 2, 2005
  5. RichardClinton

    Colin D Guest

    No, we are talking about post-shot viewing on the LCD. You can zoom the
    image with the button at top right of the camera up to 10x the original
    image size, and navigate round the image with the < and > buttons.

    Colin D, Jan 2, 2005
  6. RichardClinton

    Steve Wolfe Guest

    When I try to check for fine focus on the LCD screen, the 4x magnified
    While I can't say for sure, this is what I *think* is causing it:

    Doing full-quality decompression of a full-size JPEG from the Digital
    Rebel not only takes a fair amount of processing cycles, it also takes a
    pretty good amount of memory in which to store the image. Because of those
    constraints, when displaying the image on the LCD screen, a full-quality
    decompression isn't done - the camera does a "quick & dirty" decompression
    to obtain an image of a resolution suitable to the LCD panel, or maybe a
    small bit above. When you zoom in on the image, it's just magnifying that
    low-res version, *not* going back and performing another decompression of
    the original.

    Zooming in on a photo shot in "raw" mode seems to be a bit sharper on the
    LCD than one shot in JPEG, but still nowhere near what the LCD *could* be
    displaying if fed the proper information. Because of that, I imagine that
    the camera simply takes a down-sized version of the RAW data to display, and
    simply magnifies that to let you "zoom".

    As always, I could be wrong.

    Steve Wolfe, Jan 2, 2005
  7. RichardClinton

    Will D. Guest

    Ha! I was reading this thread and trying to imagine how these
    newfangled DSLRs got an image to the LCD on a continuing basis. Pellix
    mirrors? Mirrors that cycle > 30 Hz continuously? Noiselessly!? Walk
    around looking at the LCD instead of the viewfinder, like the non SLR
    digitals? I was starting to get excited!

    What the hell have I missed!


    Will D.
    Will D., Jan 3, 2005
  8. RichardClinton

    Colin D Guest

    Well, youve missed some, but you're in good company, as many others have
    asked the same question. DSLR's do not have preview on the LCD. They
    have optical reflex finders as in film SLR's, and the LCD will show you
    the shot after you have taken it, together with histogram info etc.

    DSLR's have mechanical shutters, and the sensor is not exposed until the
    shot is taken. Additionally, the mirror would be in the way if the
    shutter wasn't there, or was open.

    Colin D, Jan 3, 2005
  9. RichardClinton

    Will D. Guest

    Aw shoot! You mean that DSLRs are nothing more than SLRs with a digital
    sensor instead of emulsion film? Here I was all set to get excited
    about some automagical whizbang I'd never heard of before! Dang!
    Finding out that you knew what was going on all along sure is boring...

    At least with DSLRs you get an instant return mirror. The non SLR
    digitals blank out the LCD during image storage, which means that if you
    are following the action, you'd better be using the optical viewfinder,
    for whatever good that would do. With shutter lag, you won't get what
    you want anyway.

    Wonder how many people that are used to the viewfinder digitals actually
    expect DSLRs to have a continuous LCD readout? Wonder how many of those
    know what an SLR camera is? RFL!!

    Will D.
    Will D., Jan 3, 2005
  10. RichardClinton

    Rudy Benner Guest

    Ok, what's an SLR camera....;>
    Rudy Benner, Jan 3, 2005
  11. RichardClinton

    Will D. Guest

    Simple Light Rugged camera? Well, they used to be, at least compared to
    a Speed Graphic. Now, how about Super Luxurious Robot? And then if you
    ask the elite snobs that only tote a Leica M, it's probably Stoopid Loser

    What's that you say? Three strikes and out? Oh okay...

    You're up to bat, Rudy.


    Will D.
    Will D., Jan 5, 2005
  12. It just doesn't seem logical ( what else is new?) to have zoom in capacity
    that yields a blurry image. Would that it could show the area of focus
    point in greater detail. Has anyone with the hacked firmware version
    had a different experence? Why would the 17-85 IS lens give sharper zoom in
    than the 18-55? Any thoughts?

    "Mine is too, though when I got the 17-85mm IS lens, the magnified view
    on the LCD wasn't nearly as burry as with the kit lens, though it still
    is a little.

    RichardClinton, Jan 11, 2005
  13. RichardClinton

    Colin D Guest

    Well, the 17-85mm lens is a better lens than the kit lens - which is not
    to say the kit lens is not good, it just isn't as good. Also,
    autofocus, by its nature, has a tolerance built in to prevent constant
    hunting while focusing. A misfocus within the tolerance amount will not
    initiate a re-focus, so the shot can be slightly out of focus, and at
    10x up on the LCD you can see this.

    BTW, this tolerance, or hysteresis, is common to all autofocus systems,
    and not limited to any particular make.

    Colin D, Jan 11, 2005
  14. RichardClinton

    Steve Wolfe Guest

    While I can't say for sure, this is what I *think* is causing it:
    I got digging through the exif data tonight with a Perl module
    (Image::ExifTool), and found that the camera does, indeed, use a low-res
    image for display on the LCD panel. The Exif data has both a thumbnail
    image (160x120, 8k), and a preview image (1536x1024, 221k).

    For fun, I extracted the preview image, and blew it up a little bit, and
    it is of noticeably lesser quality than the original JPG - given the file
    size of only 221k, you'd expect that. The LCD has 118,000 pixels, which
    makes it (I believe) 420x280. That means that you can only zoom in to about
    a 1:4 ratio before you run out of resolution in that preview image, and the
    camera will have to start upsampling to give you something to look at. At
    higher zooms on the viewfinder, because it has to upsample, it could either
    show you something blocky and pixellated, or anti-aliased and "blurry" - it
    looks like Canon chose the blurry. : )

    Interestingly enough, there is also exif data embedded in both the preview
    and thumbnail images - exif data embedded in images which are embedded in
    the exif data embedded in an image!

    Steve Wolfe, Jan 20, 2005
  15. It might be worse than that - it may 118,000 of red + green + blue pixels,
    i.e. only about 39,000 full-colour pixels.....

    David J Taylor, Jan 20, 2005
  16. RichardClinton

    Stacey Guest

    I've been using this function on my OM E300 and it gets sharper and more
    detailed up to the 10X max, easy to see if it's a keeper or not so this
    -is- possible to do well. Just something canon decided to do this other
    Stacey, Jan 20, 2005
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