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  1. #1

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    Focusing with SFX film and SFX/R72 filter in a SLR camera

    I have done a search of the forums and opinions differ somewhat. Some say that it is as good as impossible to see through a R72 filter, although at least one member says that looking through a R72 for about 30 secs reveals the scene enough to focus. However this was the intense sun of Australia and not the much weaker sun of the U.K.

    At least one other has mentioned that his autofocus camera will work with a R72.

    So does the AF system effectively "see" sufficiently well to focus even if the eye fails to do this and is it possible for the eyes to acclimatise to the R72 filter sufficiently well to allow for manual focusing after waiting about half a minute.

    I am aware that both autofocus and manual focus are perfectly possible with a red 25A but if the "wood effect is desired then the 25A really won't "cut it"

    Thanks

    pentaxuser

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    Dear pentaxuser,

    I use a B+W 092 filter for most IR photography and I can easily focus manually with it under the type of conditions one would want to use IR. I have not attempted to use my autofocus cameras with this filter as I find a tripod necessary for good results. I find SFX gives a pleasing result hand held with a B+W 091 and I would be surprised if the autofocus did not work in bright sun.

    I hope the above is of some value.

    Neal Wydra

  3. #3

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    Thanks Neal. I'd have to re-read the info on the various filters but I will take it that a B+ 091 is the equivalent of a Hoya R72 which I know to be the same as an Ilford SFX filter.

    What attracts me to the SFX film is that while it is extended red only and not full IR it does give a good "faux" IR effect with a SFX filter and seems to be the only IR film left that is just about handholdable.

    pentaxuser

  4. #4

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    I use Cokin filters and tripod. Focusing is done without the filter and then I slidethe filter into the holder.

    Typically,I use a 24 mm ,28 mm or a 35mm lens. Set at F/8 or f/11 gives great depth of field.

    Then bracket.

    That's it.


    HowardDvorin

  5. #5
    polyglot's Avatar
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    I have a chinese-generic R72. My Minolta 5 could focus through it, and I could see through it with full sun (or at least f/11-light = EV14) and an f/2.8 lens. However, 99% of the time I would just set f/16 and hyperfocus and because there's generally a tripod involved, focus before putting the filter on.

  6. #6
    Tony-S's Avatar
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    Quote Originally Posted by pentaxuser View Post
    I have done a search of the forums and opinions differ somewhat. Some say that it is as good as impossible to see through a R72 filter
    I thought 89b (Cokin 007) was the filter of choice for SFX 200? I only use it on my Bronica GS-1 so I can't comment on autofocus lenses.


    Mission Mountains, Montana 2

  7. #7

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    TonyS I think that you are saying that through the 89b you can manually focus. I ask this as several have said that while focusing with the filter on is/may be possible they focus first and then apply the filter.

    Clearly this method may be more foolproof than with the filter on and is simpler if the filter is a drop-in to the filter holder but I had hoped to use a screw-in type which isn't so easy and may alter the focus setting.

    Nice shot by the way. Is the foreground green grass that has the silvery-white "wood effect" and not say ripe wheat that can look quite white even with an ordinary red filter?

    Thanks

    pentaxuser

  8. #8
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    I have got the focus badly off on my Mamiya RB67 using the 360mm lens wide open with an IR720 filter on the front. The very dark red image in the viewfinder is hard to see but if there is a specular highlight on the subject I can reliably focus on that....but it's wrong! The light that the eye sees, dark red, is mainly not what the film sees: infrared. The two species of electromagnetic radiation focus in different planes; at least they do on my Mamiya lenses.

    Now I focus without the filter, stop way down, add the filter, and hope. So far so good.
    Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.

  9. #9
    Bill Burk's Avatar
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    Hi pentaxuser,

    Did you know about the red mark on the lens barrel? At least all my old Super-Takumar and SMCT lenses had them. It's an infrared focus mark. You should focus optically (without a filter), make a note in you mind where the feet/meters focused and then rotate the focus away from infinity to line up where you focused onto that red line.

  10. #10
    Tony-S's Avatar
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    Quote Originally Posted by pentaxuser View Post
    TonyS I think that you are saying that through the 89b you can manually focus. I ask this as several have said that while focusing with the filter on is/may be possible they focus first and then apply the filter.
    Yes, this is what I do.

    Clearly this method may be more foolproof than with the filter on and is simpler if the filter is a drop-in to the filter holder but I had hoped to use a screw-in type which isn't so easy and may alter the focus setting.
    I see where the could be a problem. I use a Cokin filter holder, so it's not an issue for me.

    Nice shot by the way. Is the foreground green grass that has the silvery-white "wood effect" and not say ripe wheat that can look quite white even with an ordinary red filter?
    I can't recall, actually. It was in August so I suspect it was turning white at that time.

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