IR photography; efke and rollei

Film Photography & Darkroom discussion

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photocello
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Joined: Mon Sep 08, 2008 5:30 pm

IR photography; efke and rollei

Postby photocello » Mon Sep 08, 2008 5:36 pm

So I am attempting this photo project with infrared film. my professor knows absolutely nothing about it so i could really use some help!!! all of the website i have read have told me different things about how to shoot and develop...
When I meter, I meter without the R72 filter right? but when I put the filter on, does that change things?
How do I know the correct ISO? I am going to try Efke IF820 and Rollei IR 400...
I sort of understand focusing; I have the red dot on my camera, but how do I focus with it after I focus without the filter?
I know there isn't an absolute development time, so how would I go about testing my film to find the correct time? We use dektol.
Thanks for anyone who can help!!!! I really need it!!!!!


Digitaltruth
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Postby Digitaltruth » Tue Sep 09, 2008 3:48 am

The ISO setting is very misleading when using Infrared film. First of all, the film itself is sensitive to both the visible and the IR spectrum in proportions which differ from those which your light meter can interpret, so while you might find it useful to establish an ISO setting which will produce good negatives, this is mainly going to affect the visible light and not how much infrared is available. The amount of infrared light will differ substantially depending on time of day, cloud cover, etc.

When you see ISO settings such as 25, 10 or 3 listed, these are very slow and refer to the speed WITH a filter such as R72. You should meter with the filter off using the lower ISO setting, and then attach the filter. Or simply use a handheld meter.

Each filter blocks a specific amount of visible light, so you will typically find that using different IR filters requires a change of about 5 stops from the visible light reading without the filter, but you need to check and test this for yourself to get the best results. For example, Rollei Infrared IR400 is rated at ISO 400 for use without a filter, but the recommended rating with a filter is ISO 25. That is a four stop difference; however, as you can see from the test results we have published (http://www.digitaltruth.com/products/ro ... frared.php), and from times shown in the Massive Dev Chart, many people find that an additional stops of exposure are required, depending on the results you want and the filter and available levels of infrared light.

The best recommendation when using infrared film is to bracket your exposures as much as possible until you establish good results. There are many development times listed in the Massive Dev Chart http://www.digitaltruth.com/devchart.html. Dektol is a print developer, so not recommended for this purpose, although you can certainly get a result if you don't mind it being a bit grainy. You will need to determine your own time for this though by trial and error.
--Jon Mided

Digitaltruth Photo
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