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  1. #1

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    Using IR mark on lens.

    My second time out with Kodak HIE will be this morning.I'll be using a Nikon FE with a Tamron SP 28-80mm lens.
    Do I focus on my subject ,then turn the lens to the IR mark on the lens barrel?

    Thanks

  2. #2
    Steve Smith's Avatar
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    I think you've got it.

    Focus as normal then move the distance from the normal focussing mark to the IR mark.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

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    Thanks Steve.

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    Quote Originally Posted by Steve Smith View Post

    Focus as normal then move the distance from the normal focussing mark to the IR mark.


    Steve.
    I don't have a lens with an IR mark. What then?
    Tom, on Point Pelee, Canada

    Ansel Adams had the Zone System... I'm working on the points system. First I points it here, and then I points it there...

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  5. #5

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    Quote Originally Posted by Toffle View Post
    I don't have a lens with an IR mark. What then?
    g'day all

    no ir mark? the difference is very slight, use f8 or smaller and don't worry about changing focus

  6. #6
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    Quote Originally Posted by Toffle View Post
    I don't have a lens with an IR mark. What then?
    Stop down cautiously! Think in terms of the hyperfocal method- remember the basics about how to maximize DOF, and then stop down a bit more if you are worried. This logic works well for landscape, but for closeups, it's better to use a lens with an IR mark or better yet use an apo lens.
    "Only dead fish follow the stream"

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  7. #7
    Toffle's Avatar
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    Quote Originally Posted by keithwms View Post
    Stop down cautiously! Think in terms of the hyperfocal method- remember the basics about how to maximize DOF, and then stop down a bit more if you are worried. This logic works well for landscape, but for closeups, it's better to use a lens with an IR mark or better yet use an apo lens.
    This is much as I had guessed.

    I just checked the lens for my GS-1 (which I haven't used for IR) it has an IR focus mark a couple of degrees on the far side of the hyperfocal scale. By extension to my SLR lenses without a mark, would I then focus a couple of degrees on the near side? (or have I got this all backwards?)

    Cheers,
    Tom, on Point Pelee, Canada

    Ansel Adams had the Zone System... I'm working on the points system. First I points it here, and then I points it there...

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  8. #8
    AgX
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    First, there are are lenses which are said to need no correction as catadioptric lenses and those lenses special made to cope with a broad spectrum.

    Further, in literature it is stated that with lenses up to 80mm and medium aperture no focus correction will be necessary. (Old literature, prime lenses thus…)

    A common (old) rule would be:
    additional extention = focal length + focal length/250

    To get optimum results:
    Make test photos with a target placed at your typical oject distance.
    Use a caliper to measure the added extension (or more practible: marks for barrel turning)

  9. #9

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    Quote Originally Posted by Mike Kennedy View Post
    My second time out with Kodak HIE will be this morning.I'll be using a Nikon FE with a Tamron SP 28-80mm lens.
    Do I focus on my subject ,then turn the lens to the IR mark on the lens barrel?

    Thanks
    If you're using a medium or deep red filter, there's no need to adjust your focus. If you're using an opaque filter, and there's no IR markings on your lens, focus slightly in front of your subject (about 10%). You'll want to use f/8 or smaller.

    Kiron Kid
    Last edited by Kiron Kid; 10-07-2008 at 08:23 AM. Click to view previous post history.

  10. #10
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    I usually just focus a bit closer and then stop down roughly enough to preserve the DOF that I would normally have wanted before refocussing. This is the procedure I use for near-IR film (Rollei 400) with a #87 filter. I guess sfx will be quite similar, though for medium format I use lenses with IR dots so I can't say from experience. Ilford, why isn't sfx available in sheets!!!!

    AgX I am trying to guess where that number 250 comes from, do you have a quick answer? I can't think of any universal reason why it should be so. I mean, doesn't it depend critically on the sensitivity of the film, the cutoff of the filter, and last but not least how much ED glass the lens has versus non-ED? Is it because the index of refraction for glass is all roughly the same?
    "Only dead fish follow the stream"

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