Manual Focus Digital Camera Low-Res Display, HOW?

Discussion in 'Digital Photography' started by mike, Jun 17, 2004.

  1. mike

    mike Guest

    I got the 640x480 CF camera for my HP Jornada 548 PDA.
    It takes way better pictures than I expected...IF I can
    get it focused.

    With the low res, low contrast screen, there's just not enough
    resolution to set the focus accurately for close-ups. If there's any
    ambient light, forget it. I'm mainly interested in getting usable
    schematic copies when I find 'em at swap meets. The camera seems to be
    able to do a decent job on half a page...IF I could reliably focus it.

    I noticed messing around with my webcam...if there are parallel lines,
    like a grille or screen, there are interference patterns set up with
    the pixels. I can sorta use that to focus.

    Rather than reinvent the wheel, is there some information available on
    how to make a small "coupon" that can be placed on the object to
    focus based on those interference patterns?

    Thanks, mike

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    mike, Jun 17, 2004
    #1
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  2. mike

    Lionel Guest

    Kibo informs me that mike <> stated that:
    >I noticed messing around with my webcam...if there are parallel lines,
    >like a grille or screen, there are interference patterns set up with
    >the pixels. I can sorta use that to focus.
    >
    >Rather than reinvent the wheel, is there some information available on
    >how to make a small "coupon" that can be placed on the object to
    >focus based on those interference patterns?


    You're thinking of a focusing target, & it doesn't need anything fancy
    to do the trick for most autofocus systems.
    Try printing out a page covered in uppercase 'X'es (preferably in a
    serfied font, such as Times Roman) & just cut it into small (1/2" x
    1/2") squares, & place one on the part of the subject covered by the AF
    point.

    --
    W
    . | ,. w , "Some people are alive only because
    \|/ \|/ it is illegal to kill them." Perna condita delenda est
    ---^----^---------------------------------------------------------------
    Lionel, Jun 17, 2004
    #2
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  3. mike

    mike Guest

    Lionel wrote:
    > Kibo informs me that mike <> stated that:
    >
    >>I noticed messing around with my webcam...if there are parallel lines,
    >>like a grille or screen, there are interference patterns set up with
    >>the pixels. I can sorta use that to focus.
    >>
    >>Rather than reinvent the wheel, is there some information available on
    >>how to make a small "coupon" that can be placed on the object to
    >>focus based on those interference patterns?

    >
    >
    > You're thinking of a focusing target, & it doesn't need anything fancy
    > to do the trick for most autofocus systems.


    Thanks, but the subject line clearly states "manual focus". There is no
    automatic focus. There are not enough pixels on the display to resolve
    fine details that can be captured by the sensor. I'm looking for a
    TRICK, like using aliasing between the image and the display pixels
    to obtain better, easier, more repeatable focusing for macro shots.

    Thanks, mike

    > Try printing out a page covered in uppercase 'X'es (preferably in a
    > serfied font, such as Times Roman) & just cut it into small (1/2" x
    > 1/2") squares, & place one on the part of the subject covered by the AF
    > point.
    >




    --
    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Yaesu FTV901R Transverter, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
    mike, Jun 17, 2004
    #3
  4. mike

    Lionel Guest

    Kibo informs me that mike <> stated that:

    >Thanks, but the subject line clearly states "manual focus". There is no
    >automatic focus. There are not enough pixels on the display to resolve
    >fine details that can be captured by the sensor. I'm looking for a
    >TRICK, like using aliasing between the image and the display pixels
    >to obtain better, easier, more repeatable focusing for macro shots.


    Yes, my mistake, Mike.

    For manual focus, a better method would be to print a checkerboard
    pattern, preferably with graduated grid sizes. That'd give you the kind
    of visual cues that you're talking about.
    A finely printed, B&W laser-printed grid should give you visible colour
    moire or shimmer on a good focus.

    --
    W
    . | ,. w , "Some people are alive only because
    \|/ \|/ it is illegal to kill them." Perna condita delenda est
    ---^----^---------------------------------------------------------------
    Lionel, Jun 18, 2004
    #4
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