Getting Started in Black and White Infrared Photography
by Bill Helsel, 5/2008
What is infrared photography?
Visible light---the light we can see with our eyes---is only a tiny part of the broad spectrum of electromagnetic radiation produced by the sun and other sources. Just beyond the color red in the visible part of the spectrum lies a broad band of invisible radiation called infrared. While we can’t see infrared, we can photograph it using a few special films or modified digital cameras that are sensitive to near infrared light as well as visible light. (We aren’t photographing heat. It’s carried only by far infrared radiation which is nowhere near visible light on the spectrum of electromagnetic radiation.)
Using these special films or cameras, you can photograph the world as it appears with a mixture of visible and invisible (near infrared) light. By using filters you can cut out some or even all of the visible light, producing a photo of a scene lit mostly or even entirely by infrared light. The results can be strange and magical because many things in nature reflect much more (or less) infrared light than visible light. For example, the chlorophyll in green plants reflects a lot of infrared, so grasses and trees usually appear very pale in an infrared photo. Blue skies reflect very little infrared, so they can appear almost black in an infrared photo. With practice you can learn to roughly anticipate how a scene will look in infrared, but there are often surprises.
Doing it Digitally
Infrared light is detrimental to the formation of a good color digital image, so almost every digital camera has an infrared-reducing filter right in front of the sensor. On many older cameras these filters are inefficient enough to allow some IR light to pass through, enough to form an IR image when most or all visible light is blocked by a special filter mounted on the front of the lens. For a simple IR sensitivity test, try photographing the business end of a TV remote control while holding down a button like Volume Up that produces a continuous beam of IR. If your camera records a point of white on the remote control, it should work for IR photography. I recommend using a Hoya R72 or Wratten #87 filter. These block almost all visible light, so with an SLR you must compose and focus (manual only) with camera on a tripod, then add the filter. Cameras with “live view” screens have an advantage here because you can see the IR image with filter in place. Some built-in light meters read accurately through these filters and some don’t, so test to be sure. Exposures for landscapes are often several seconds unless you use a very high ISO and/or very large aperture (neither of which is usually helpful in making high quality images). Glass versions of the filters I recommend can be quite expensive, but you can buy a 4” square acetate #87 for $27 from Freestyle Photo Supplies (www.freestylephoto.biz). These filters are very thin and easily scratched, and you must still rig something to mount them on your lens, but they work well. Some digital cameras can be converted for IR by replacing the anti-IR filter with something like a #87, or with an optically-equivalent IR-transparent filter (in which case you still need an IR filter on the lens). These conversions cost about $300-500. Two cameras currently made by Fuji for forensic or scientific use come already adapted for IR use. For lots more info about digital IR and examples of IR photography, Google “digital infrared photography”.
Most film cameras work well with IR film, with the exception of a few newer 35mm cameras with built-in motorized film advance which use a tiny IR beam to count sprocket holes when film is advanced. These IR beams fog the edge of IR film and the fogging may spill into the image area. 35mm IR film (except for Ilford) must only be removed from its plastic can and loaded into the camera in total darkness. The same goes for unloading the film and putting it back into the can. Otherwise IR light can penetrate the felt light trap on the cassette and fog part or all of the roll. 120 rollfilm, having no cassette or light trap, seems to be safe for loading and unloading in deep shade or other dim areas. For many years Kodak made High Speed Infrared film which produced the grainy, highlight-flared IR images you are likely to have seen. Sadly, Kodak discontinued this film for lack of sales at the end of 2007. Three films sensitive to IR remain on the market, though none record as far into the IR spectrum as Kodak: Efke IR820 is the most IR sensitive, nominally ISO 100 (I rate it at 50), comes in 35mm, 120 (both about $10 per roll), and sheet film sizes. Rollei B&W Infrared is a little less IR sensitive, nominally ISO 400, comes in 35mm, 120 (both about $10 per roll), and 4x5”. Ilford SFX200 is the least IR sensitive, yielding a semi-IR look with a deep red filter, but is a good all-purpose fine-grain ISO 200 BW film. Available in 35mm (about $9 per roll) and 120 (about $8 per roll). Freestyle (www.Freestylephoto.biz) sells all of these films. All so-called IR films are fully sensitive to visible light, so without filtration they produce a conventional BW image. Using filters that eliminate varying amounts of the visible spectrum allows us to control the intensity of the IR effect. For a mild effect with Efke and Rollei, use a medium red (Wratten #25, B+W 090) filter. A deep red (Wratten #29, B+W 091) filter is stronger, and the Hoya R72 or Wratten #87 eliminate all visible light for the strongest IR effect. These are the filters I work with. Several other filters that fall near or between these in strength of effect are also available. #87 glass filters are quite expensive, but you can buy a 4” square acetate version for $27 from Freestyle. Just be aware that they scratch easily and you must rig or buy some sort of holder to mount the filter on your lens, and that no light must get between the front of your lens and the filter. Most through-the-lens light meters (built into camera bodies) meter pretty accurately through the red filters, but not well (or at all) through the opaque filters (R72, #87 and the like). For opaque filters I usually increase exposures 3 stops over the meter reading I get with a deep red filter. Bracketing exposures at full stops is always a good idea till you have had a lot of experience with your particular camera, film and filter. Black and white IR film is processed like any other BW film (except for the need to handle it only in total darkness), so you can process it in a home darkroom or take it to a good pro-quality photo lab which has had experience processing your particular film. Always ask before trusting a lab with your film.
There’s one more quirky thing about shooting infrared on film or digital: IR light comes into sharp focus a bit further behind a lens than visible light does, so you must focus a little closer than normal and, if possible, use a small aperture (high number f stop) to cover any focus error. How much closer to focus? Fixed focal length lenses (“prime” or non-zoom lenses) usually have a tiny “R” or red dot on the lens barrel near the focus reference mark. Just focus normally, then shift the focus scale distance that lines up with the reference mark over to the “R” and you’ll find you’re focused a little closer. With zoom lenses, it’s trial and error. Usually focusing on the closest important part of a scene, instead of somewhere in the middle, will get you close.