Infrared exposure metering (Efke IR 820)

Discussion in 'Exposure Discussion' started by Top-Cat, Feb 2, 2010.

  1. Top-Cat

    Top-Cat Member

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    No matter how many posts I browse through online I just can't seem to find the one that suits me.

    I bought some Efke IR 820 finding it's one of the only real infrared films still available (Both Rollei and Ilford seem to be more of a BW film with extended red sensitivity). Being a cheapskate I got myself some unexposed developed slide film to use as a sensor, I also have a Hoya 25A, but won't be using it this time.

    So now to get the real IR shots, but how?

    The problem seems to be getting the exposure right when using stronger IR filters, I'm hoping my solution with using a Sekonic Flashmate L-308 with a bit of the slide film over the sensor as a filter might get the exposure right, but testing it I'm not so sure. It seems to react with rather short exposure times near the hot sources, like close to the lamps or in the warmer rooms, but won't give me any answer when trying it in the middle of the room. It just doesn't seem to give any result at all for the overall exposure of a larger image.

    Is there any other way of getting exposure correct, like setting it to an especially low ISO, or maybe I should use the exposure I get when putting the meter in front of the warmer sources in the room?

    Just how do I guess the exposure for this film, I'll probably need to bracket, but I still need to find the estimated exposure time and aperture for the film so I have something to work around.
     
  2. tiberiustibz

    tiberiustibz Member

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    I purchased a Hoya 72 on ebay for less than $20. I found that to be very effective. You're looking at an ASA of about 3 or less.
     
  3. Top-Cat

    Top-Cat Member

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    I just did a bit of research and ended up with this.

    According to this source - http://people.rit.edu/andpph/text-infrared-filter.html - a sheet of unexposed processed slide film is the equivalent of a Wratten 87 filter, now this study is made using Ektachrome, but I'll just have to gamble and use the Velvia that I have for the same purpose.

    Now according to Efkes fact sheets - http://www.mahn.net/TA820ce.pdf - though it doesn't supply the data for a Wratten 87 filter (only 89B) I'm guessing it's somewhere between the RG 645 and RG 695.

    The conclusion being that I should set the light meter to ISO 6 or 9 and expose according to that.

    If anyone has any real experiences using Efke IR 820 film with a seperate light meter I'd be glad to hear it.
    At least I'm just a little bit closer to getting it right.
     
  4. ras351

    ras351 Member

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    Proper exposure is going to vary a lot with developer, time of day, time of year, location and filter. What works for me, and provided the sun is shining, is to meter at EI50 and add 5 stops for the 89B and 6 stops for the 87. This is when developed in ID11 1+1 for I think 12 minutes (notes are at home so I can't confirm the time). The 87 has a higher cutoff than the 89B (ie it lets through less at the visible end of the spectrum) and hence will need more exposure. I would still bracket a stop either way when possible.

    Roger.
     
  5. David William White

    David William White Member

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    I've shot a box of it with a Lee 87 filter. Before wasting sheet film, I tested with a roll of 120, and bracketed by two stops all the way down to ISO 0.25. (Yes, two stops more than ISO 1). That's where I found printable negatives. Way into reciprocity failure territory. I posted one or two here a couple of summers ago. I now occasionally shoot it in 4x5 at roughly ISO 0.25 and can print from those negatives. I did a couple last month in a greenhouse, roughed them in at about 0.5, and they were on the thin side, and wish I had taken a longer coffee break while the shutter was open. But they do exhibit wonderful IR characteristics.

    I would understand if you find this unbelievable. I'm guessing the Wratten 87 is the same as the Lee 87. So I would encourage you to follow all the advice and rate as low as you can, and be prepared to go lower. Have courage and good luck.
     
  6. Top-Cat

    Top-Cat Member

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    I'll probably be using either Xtol or Tmax as a developer, if anyone has any developing dilutions and times for that.
     
  7. Mike Richards

    Mike Richards Member

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    My Test Results

    Did considerable testing a few years ago and came up with this ISO table. I believe your EFKE 820 is the same as the old Maco:

    Film_________________Kodak HIE___Konica 750__Ilford SFX__Maco 820c
    Filter B+W 090 (w25)__ISO 50______ISO 12______ISO 25_____ISO 12
    Filter B+W 091 (w29)__ISO 50______ISO 12______----________ISO 12
    Filter B+W 092 (w89B) ISO 25______ISO 8_______----________ISO 6
    Filter B+W 093 (w87C) ISO 12______------_______----________------

    Where ----- indicates not practically usable; w-wratten designation.

    Hope this helps.
     
  8. Robert Hall

    Robert Hall Subscriber

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    I would agree with the iso of .25 or 1/4. Metering with a visible light meter is fraught with danger as they are calibrated to visible light and not IR.

    Sunny 16 rule for Efke IR::: 4 seconds at f/16 using something around 695nm cut off filter.

    If you decide to bracket, don't bother with underexposure as it rarely results in anything useful. This film is substantially slower than the Maco IR I used to use and I rated it at about one half asa or 2 seconds at f/16

    Best of luck.
     
  9. Andrew O'Neill

    Andrew O'Neill Subscriber

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    If you want infra-red effects with this film you need to expose through an opaque filter such as a #87. I expose Efke 4x5 IR film at EI 1.5. My metre only goes down to EI 12, so I have to add 3 stops before I make my exposure. On a bright sunny day in summer, that translates to about 22 sec at f/11 (with reciprocity effect added).
    I sure miss Kodak infra-red film! Now that was a true infra-red film.
     
  10. holmburgers

    holmburgers Member

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