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  1. #1
    winger's Avatar
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    IR with or without autofocus

    I know the infrared assist in some cameras can mess up IR film. Does this only happen if you use the autofocus? Or is the IR assist "on" at all times? I have a Pentax PZ1P and am pretty sure it has some type of assist 'cause I could see a red beam when shooting in a cave this spring. So, would it be safe to try HIE in it as long as I don't use the AF ('cause I rarely use AF anyway)?

  2. #2
    David A. Goldfarb's Avatar
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    You probably should use manual focus anyway, unless your autofocus camera can compensate for the IR focus shift.
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    winger's Avatar
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    So the "IR assist" will only interfere if use autofocus?

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    David A. Goldfarb's Avatar
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    Isn't the IR assist for AF in low light? I don't believe it is related to shooting IR film.

    With most lenses, IR light will focus at a different point than visible light.

    On a manual focus lens for a 35mm camera, there is usually a red dot on the focus scale for IR focus. To focus with IR film, the normal practice would be to focus conventionally, look at the focus scale on the lens, and then move the focus ring from the regular focus index mark to the red dot. The image will look slightly out of focus in the viewfinder, but it will be in focus for IR film.

    Unless the AF program on your camera can make this adjustment automatically for IR, you shouldn't use AF for IR film.
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  5. #5
    winger's Avatar
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    The IR assist is for low light for AF. I ask mostly 'cause I don't normally use AF, but wonder if it would prohibit my using this camera for IR film whether I'm using Af or not. I've seen it recommended to not use cameras that have the IR assist with IR film, but if the camera only uses it when autofocusing, then I wonder if it really isn't a problem.

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    I think you're confusing IR focus assist with IR sensing of sprockets for the motor drive in cameras like some EOS's and Contaxes. I bit the bullet and ran some HIE through my G2, it didn't seem to make much difference.

    David is right though, standard AF will focus in the wrong place for IR. Your lenses probably have a red dot to mark the correct offset.

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    winger's Avatar
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    I don't use autofocus and wouldn't with IR film anyway (I've used HIE before and know how to focus). I don't know if my Pentax PZ1P will mess up the HIE. That's what I'm trying to find out (preferably without shooting a roll as an experiment).
    Since it has the IR assist with AF, does it also use IR for anything else that would then mess up HIE?

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    kaiyen's Avatar
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    For what it's worth, I've found that, when using a red 25, enough visible light gets through that the subject still looks in focus, even with AF. I see no significant loss in sharpness.

    allan

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    Quote Originally Posted by winger
    I don't use autofocus and wouldn't with IR film anyway (I've used HIE before and know how to focus). I don't know if my Pentax PZ1P will mess up the HIE. That's what I'm trying to find out (preferably without shooting a roll as an experiment).
    Since it has the IR assist with AF, does it also use IR for anything else that would then mess up HIE?
    How does your camera count the film? When you open up your camera back, is there a little opaque looking window inside? If so, this is the IR sensor used for counting the sprockets on the film (and is what has the possibility of fogging the Kodak HIE IR film).
    Diane

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  10. #10
    winger's Avatar
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    Quote Originally Posted by colrehogan
    How does your camera count the film? When you open up your camera back, is there a little opaque looking window inside? If so, this is the IR sensor used for counting the sprockets on the film (and is what has the possibility of fogging the Kodak HIE IR film).

    Thank you - I'll check. You're the only one who 'got' what I was asking.

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