camcorder through car window glass

Discussion in 'Professional Video Production' started by Rick Merrill, Feb 9, 2007.

  1. Rick Merrill

    Rick Merrill Guest

    Will the autofocus work through a car window?

    What else should I be asking?
     
    Rick Merrill, Feb 9, 2007
    #1
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  2. Rick Merrill

    Mike Fields Guest

    If it is IR focus, you may have a problem, but my Sony TRV520
    seems happy shooting through the window. DON'T let it touch
    the window or you get the vibration "float" it as much as possible
    (the less coupling you get to the car/vehicle, the better the image.)
    You may find simply setting it on manual works best (things going
    by close like a bush next to the road drive the autofocus nuts - and
    you).

    mikey
     
    Mike Fields, Feb 9, 2007
    #2
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  3. "Rick Merrill" wrote ...
    Depends on what kind of autofocus it is.

    Ultrasonic will clearly focus on the inside surface of the
    window. Even window/door screens will confuse them.

    Infrared may or may not, depending on several conditions.

    The kind that analyzes the video image likely has the best
    chance of working properly through a window. I believe that
    is the most common kind we see in recent products.
    Why you should consider using autofocus at all?
     
    Richard Crowley, Feb 9, 2007
    #3
  4. It will. But might get a little confused when the sun hits the windshield,
    and when it sees low-contrast areas. But why would you want to use
    autofocus anyway in this situation? You won't have any benefit from it, as
    no subjects will get close enough to require a decent focus readjustment.
    You're better off working in manual (set to infinity, with a high
    aperture).

    cheers

    -martin-
    --
     
    Martin Heffels, Feb 9, 2007
    #4
  5. Rick Merrill

    BlahDiBlah Guest

    It's a bit obvious, but I'll say it anyway... remember to clean the window!
    :)
    Any dirt on the glass won't help the autofocus...

    Gareth
     
    BlahDiBlah, Feb 9, 2007
    #5
  6. Rick Merrill

    Rick Merrill Guest

    The 'subject' may change from 300 ft to 2 ft pretty quickly
    plus I' may or may not have a way to support the camcorder
    other than with my hands alone.
     
    Rick Merrill, Feb 9, 2007
    #6
  7. Rick Merrill

    Rick Merrill Guest

    Dang! That's a good idea that had not occurred to me at all!

    (i.e. it's not my vehicle)
     
    Rick Merrill, Feb 9, 2007
    #7
  8. Rick Merrill

    FCP User Guest

    First off, this is WHY manual focus is such an important camera feature.

    Second, shooting through glass - a polarizing filter is your friend.

    Third, have fun!


    For what it's worth.
     
    FCP User, Feb 10, 2007
    #8
  9. Don't worry too much. If you would have a focal length of 6mm (wide angle),
    and an aperture of 5.6, then at 2 ft you are in-focus from 0.9ft -
    infinity. If you're shooting during the day, you will have an even smaller
    aperture and an even higher depth-of-field (this all assuming you have a
    1/3" CCD).
    You can work it all out for yourself at
    http://www.panavision.co.nz/main/kbase/reference/calcFOVform.asp
    And then you can pick your optimal numbers. If you focus on the
    hyperfocal-distance, you will be in focus from the minimum calculated till
    infinity. So, say in this example the hf is 1.9ft, min is 1.1 ft, max is
    infinity.

    cheers

    -martin-
    --
     
    Martin Heffels, Feb 10, 2007
    #9
  10. Rick Merrill

    Mike Fields Guest

    Polarizers often give very odd results through tempered glass.
    Watch for strange "blotchy" patterns when using one - some
    windshields are fine, others .... eeeeeeek !!

    mikey
     
    Mike Fields, Feb 10, 2007
    #10
  11. Rick Merrill

    Mike Fields Guest

    Maybe he *wants* the picture of that dead bug?? :)
     
    Mike Fields, Feb 10, 2007
    #11
  12. Rick Merrill

    Rick Merrill Guest

    Hooo, a polarizer would be good shooting into the sun.

    Anyone produced a Police Video? - tagging along with the constabulary -
     
    Rick Merrill, Feb 10, 2007
    #12
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