No human can see infrared; color film can only record and interpret it. Kodak Ektachrome Infrared Film 2236 was originally devised for camouflage detection. Its three image layers are sensitized to green, red, and infrared instead of blue, green and red. Later applications were found in medicine, ecology, plant pathology, hydrology, geology and archeology. Its only pictorial use has been to produce weird color effects.
In use, all blue light is filtered out with a Wratten 12 filter; visible green records as blue, visible red as green, and infrared as red. The blue, being filtered out, is black on the reversal color film. Because visible yellow light is used as well as infrared, focus is normal, and the use of a light meter is normal for this part of the spectrum. What happens to the infrared reflected light is not measurable by conventional methods, so testing is advisable. A suggested EI for testing prior to production is daylight EI 100 with a Wratten 12 filter.
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