October 7th 2007
Prior to dismantling and potentially destroying a perfectly good digital camera for the sake of an infrared modification, I have embarked on an simpler way to achieve the same effect. What it boils down to is this: the CCD on your average ordinary digicam absorbs infrared light quite effectively, so much that camera manufacturers try their hardest to block IR from ever reaching the detector. They install an IR-blocking filter behind the lens that mops up most but importantly not all infrared from getting through. So it’s actually possible to take an infrared picture using an unmodified digital camera, if you trick it. By placing a filter in front of the lens that blocks out every thing *but* infrared, you can in fact produce an IR image.
I went to a photo store and picked up a sheet of Roscolux #27 “Medium Red” filter gel. If you look at the transmission curve for this filter you will see that it blocks out pretty much all of the visible spectrum except for red and beyond. Then I took a few test shots out on the street, using 8 pieces of the filter gel to make my IR images. The downside to this method is that you need to take very long exposures (ie: use a tripod), and the images are a little blurry from the thickness of plastic in front of the lens. But it definitely works. The green of the trees turns snow white after a little post processing.
N.B. The color channels of the images with the filter still contain some useful information, and if you fiddle around with them in photoshop you can get some bizarre effects. Here I have done autolevels and then swapped the red and blue channels (you do this with the “channel mixer” tool in PS).