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Thread: Exposre of infrared film

  1. #1

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    Exposre of infrared film

    I have been experimenting with Maco infrared film and am finding it v. difficult to estimate exposure. With the if filter in place the film seems to have a max speed of about 6ASA. Is there less infrared radiation earlier in the day than at midday? or later in the day? I understand that there is no substitute for bracketing but is there some rules of thumb that I could apply? Many thanks in advance. Yaakov Asher Sinclair

  2. #2

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    Exposre of infrared film

    I set my incident light meter to ISO50 and use either a #25 Red filter or Heliopan RG695 (visually opaque) filter over the camera lens. There is more infrared "effect" using the RG695, but is far easier to focus and compose using the #25 red and the results with the #25 are more than acceptable. I develop using Ilfosol-S 1+9 for 7 minutes @ 20'C or D-76 stock for 8 minutes @ 20'C; agitating and fixing like it was Ilford 100 Delta.

    I have found that clear blue winter sky with a few whisps of cloud results in the "blackest" sky in (using IR820c or HIE). During the spring/summer/fall, the sky is almost always lighter. I usually photograph between 10am and 3pm when visible light is strongest and does not emphasize the pollution in the atmosphere as much (as it does during sunrise and sunset when sunlight angles through the sky).

    Hopefully this gives you a starting point. Shoot a couple of rolls of IR820C in the more afforable/expendable 35mm format and bracket 1.5 stops plus/minus to set your own personal film speed. I have always been a fan of HIE, but the tighter grain and anti-halation layer of the Maco film has since won me over. Cheers,

  3. #3

    Exposre of infrared film

    In bright sun with an ir filter is is about EI 2-3 , somewhat faster with 25 red.

    Any time the sun is out FULL the IR exposure is the same. Open 1 stop for a cloud in front of the sun.

    If required, I place my it filter infront of my spot meter. The EI used is not the true EI as now you are really using the IR sensitivity of the cell which wasn`t designed for this use. For HIE, I use 800 on my Pentax digital. The best thing is to measure a highlite and a shadow thru the filter and average them.

    Using HIE, f 6.3 1/250 with my Leica IR filter seems to seems to always work in full sun. The camera meter behind the lens confirms this if I set it to 800. Then I can measure in deep shade too. I no longer bracket.

  4. #4

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    Exposre of infrared film

    I echo Moe's 50 asa settings. I would develop in Rodinal at standard dilution for 7-8 minuts. Don't hesitate to try a couple of brackets on the first outting as everyone has a different interpretation of how the final negative and print should look. It is always interesting though. Good luck.

  5. #5
    Moderator Ralph Barker's Avatar
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    Exposre of infrared film

    The amount of IR available for reflection by the scene is essentially a function of the angle of the sun and the amount of atmosphere through which the light passes. Thus, exposure is affected by both season (time of year) and time of day, along with altitude and location.

    To complicate matters further, exposure is also affected by the IR sensitivity point of the film, and the cutoff point of the filter being used. Using a filter with a lower cutoff point will transmit more visible-spectrum light, along with the IR, so the exposure will be reduced. But, so will the IR effect seen in the negative and print. If an IR filter is used that has a cutoff higher than the sensitivity point of the film, essentially no light to which the film is sensitive will be transmitted, and the negative will be essentially clear.

    Maco 820c has a sensitivity point of 820nm, meaning that it will respond to light up to that wave length. As I prefer to maximize the IR effect, my preference is to use either an 89b or 87 filter with that film. For a September early afternoon exposure at my latitude (San Jose, CA), I found the optimum exposure to be about 8 stops down from the incident meter reading using an 89b filter, which transmits almost no visible-spectrum light. Here's an example with the 89b:




  6. #6
    Moderator Ralph Barker's Avatar
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    Exposre of infrared film

    This table may help with the wavelength cutoffs:

    <table columns="5" border="1" width="100%">
    <tr>
    <td>Film</td>

    </tr>

    <tr>
    <td>Wratten #25</td>
    <td>std red, x5(2.3)</td>
    <td>B+W 090</td>
    <td>600 nm</td>
    <td>.</td>
    </tr>

    <tr>
    <td>.</td>
    <td>.</td>
    <td>various gel, resin</td>
    <td>.</td>
    <td>.</td>
    </tr>

    <tr>
    <td>Wratten #29</td>
    <td>dk red, x8(3)</td>
    <td>B+W 091</td>
    <td>620 nm</td>
    <td>.</td>
    </tr>
    <tr>

    <td>.</td>
    <td>.</td>
    <td>various gel, resin</td>
    <td>.</td>
    <td>.</td>
    </tr>

    <tr>
    <td>.</td>
    <td>dk red</td>
    <td>B+W 092</td>
    <td>650 nm</td>
    <td>.</td>
    </tr>

    <tr>
    <td>Wratten #70</td>
    <td>.</td>
    <td>.</td>
    <td>680 nm</td>
    <td>.</td>

    </tr>

    <tr>
    <td>Wratten #89b</td>
    <td>moderately opaque†</td>
    <td>Hoya RM72</td>
    <td>720 nm</td>
    <td>.</td>

    </tr>

    <tr>
    <td>.</td>
    <td>.</td>
    <td>Kodak gel</td>
    <td>.</td>
    <td>.</td>

    </tr>
    <tr>
    <td>Wratten #88A</td>
    <td>.</td>
    <td>.</td>
    <td>750 nm</td>
    <td>Konica 750, 35mm, 120</td>

    </tr>
    <tr>
    <td>Wratten #87</td>
    <td>mostly opaque†</td>
    <td>Tiffen glass</td>
    <td>800 nm</td>
    <td>.</td>

    <tr>

    <tr>
    <td>.</td>
    <td>.</td>
    <td>Kodak gel</td>
    <td>.</td>
    <td>.</td>

    <tr>

    <tr>
    <td>.</td>
    <td>.</td>
    <td>Lee polyester</td>
    <td>.</td>
    <td>.</td>

    </tr>

    <tr>
    <td>.</td>
    <td>.</td>
    <td>.</td>
    <td>up to 820 nm</td>
    <td>Macophot 820c, 35mm, 120, 4x5, 8x10</td>

    </tr>
    <tr>
    <td>Wratten #87C</td>
    <td>totally opaque†</td>
    <td>B+W 093</td>
    <td>850 nm</td>
    <td>.</td>

    </tr>

    <tr>
    <td>.</td>
    <td>.</td>
    <td>Kodak gel</td>
    <td>.</td>
    <td>.</td>

    </tr>

    <tr>
    <td>.</td>
    <td>totally opaque†</td>
    <td>Hoya RM90</td>
    <td>900 nm</td>
    <td>Kodak HIE (up to 900 nm, max 750-840 nm), 35mm only</td>

    </tr>
    <tr>
    <td>Wratten #87B</td>
    <td>totally opaque†</td>
    <td>.</td>
    <td>940 nm</td>
    <td>.</td>

    </tr>
    </table>

    † "moderately opaque" means that brightly lit elements can be seen as deep red through the filter; "mostly opaque"
    means that only very bright spectral reflections, such as highlights on chrome, can be seen as deep red; "totally opaque" means that no visible light is transmitted.


  7. #7

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    Exposre of infrared film

    Many thanks for all the help!

  8. #8

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    Exposre of infrared film

    I've found that I get better IR results from the Maco films with either an 88A or 87 filter. Ralph, what kind of exposure time/aperture did you use to get that shot with the 89B?

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