Notes on Digital Infrared Photography

Infrared light is by definition “invisible” light that resides above the threshold of human vision. It is not Kirilian, or aura photography, though it sometimes creates an ethereal, ghost-like representation that can be quit seductive. Like most things photographic that appear visionary, there is a bit of science behind the magic. This involves disabling the “normal” operation of the camera to allow infrared level light to record, something that is usually blocked by an IR cutout filter placed in the light path from lens to sensor. It turns out that without this internal filter the digital image would be “polluted” with IR, and would, for most people, create less than desirable image quality. In truth, digtal sensors often have considerably more infrared sensitivity than was previously thought.

In most cameras the filter is “hard wired” into the construction, which means that if you remove it you now have a fulltime IR capable camera that cannot be returned to normal use. This must be done by a service company that knows its stuff; it’s something you cannot do on your own. Some cameras come IR dedicated, mostly those used by law enforcement agencies for gathering forensic evidence. A very few can be do-it-yourself infrared, such as the Sigma model DSLRs, where you can remove the lens and literally pick out the IR filter (which doubles as a dust filter), albeit very carefully. Those who are true IR fans would do well to investigate the cameras used by police departments. Another course is having a custom IR setup put into the camera by a service company. This goes beyond removing the IR cutout filter; it involves replacing that filter with one that makes the camera IR ready and capable of shooting IR without placing a filter over the lens, which is what you need to do with a camera whose IR cutout filter has been removed. This is the easiest course to take as shooting with a dark IR filter over the lens can make it difficult to focus and compose.

To capture IR images with a cutout filter removed camera you place a filter over the camera lens, something that is uncommon for most digital photography (as most filter effects can be added later in software.) While you can shoot IR without any filters with a cutoff filter removed camera you will get a sort of reverse pollution of visible light, something that diminishes, but does not always completely ruin the IR effect.


There are three levels of filter that can be used, with one being quite expensive and, in my experience, unnecessary to gain the effect. The filters used include a red filter, something black and white film photographers might still have in their closet, (a Wratten 25A), plus two filters that block more and more visible light and do not allow for image recording below the infrared threshold. The two other filters, which go under various names and codes according to the filter maker’s markings, block light under 700 nanometers and 830 nanometers (and some higher) on the spectrum; in other words, progressively more refined IR light. The higher blocking filter gets very expensive and is only for both purists and aficionados.

You can choose to work in regular RGB mode or in Monochrome mode as you shoot; perhaps Monochrome mode would be easier as it removes the red cast over the image, but it certainly does not give you a real clue as to what you can do with the image later. That will come with experience. I always shoot IR (and all my images) in Raw mode.

The effects with filters can be amazing but you cannot see what’s going on in the viewfinder, which means that you have to frame and focus prior to exposure, or figure out some way to view over the top of the camera for an approximate view. The red filter, while not as “pure” lets you at least see what’s going on in the finder. If you are an IR fanatic then the blockers will be your choice—those who dabble in it, as I do, will find the red filter is fine. However, if you plan to shoot IR a lot, then get a camera that is IR ready, one that’s been converted by a service company.

The procedure some use for shooting is to purchase a filter that is a bit larger than the largest diameter lens they own (thus it can be used on all the lenses owned) and to first frame and focus the tripod-mounted camera, then hold the filter over the lens when the exposure is made. This can result in some light leak that is usually eliminated with some practice in proper holding of the filter. Exposure is set manually. Some bold photographers shoot handheld in the same fashion, viewing over the top of the camera pentaprism to yield an approximate framing and shooting a bit wider than they normally would for a “fudge” factor to which they can apply a more specific cropping later.


Exposure has nothing to do with making readings and using metering patterns, since you are not dealing entirely or at all with visible light. It’s a strange concept, but that’s also part of the IR mystique—being out of normal bounds of having to read exposures and balance highlight and shadow. The best way to work IR exposures is to start at somewhere around f/11 at 1/125 second and then review the image after exposure and adjust accordingly. The view in the finder is quite different than you’d expect, so you will have to gain experience with what a processed IR image looks like according to a certain exposure level. This is the only way you will be able to make predictions about what the correct exposure might be, or at least what it should look like upon playback.

There is something in IR known as a “focus offset”, which means IR light bends a bit differently and may arrive at the sensor plane in different fashion than normal or visible focusing. This will become critical when doing close-ups, but does not have much effect in my experience for photos made beyond six feet. I often shoot at f/11 or narrower with a fairly wide angle lens just to take up that slack, changing the shutter speed accordingly.


IR black and white has always been near and dear to landscape photographers, and now that high-speed IR black and white film has been discontinued by major film makers digital seems to be the only way to go.

Scanning for Black and White

Many of us who worked prior to the turn of the century, and even somewhat around that bend, shot with film. The following is for those who still work with film and combine film exposure and development with digital scanning and printing, to me a very good course to follow, and for those who have older film images they want to print or digitize. While I now photograph mostly with a digital camera, I also have lots of “legacy” film to work with, and recommend scanning and inkjet printing as the most sensible and creative means to realize those older images.

The main thing to keep in mind when scanning is to “do no harm.” There are various schools of thought on this, but my approach has always been to get as much image information out of the film as possible without doing any, or many corrective procedures beyond that which the scanner might offer. The scanner is there to pull information out of the film record and turn that information to digital form. Scanner software can enhance that information or add to it; use it to record, not overly enhance. You should also scan at the maximum optical resolution of the scanner, and not to work with “interpolated” resolution, that is, to not add to the information through algorithms. If the scanner you use does not create the amount of information you require for your prints—in other words, produces less resolution that you need for a particular image size—then get another scanner or have the images scanned by a pro lab.

Scanners vary greatly in their specs and capabilities, and new models come out periodically, so I will not recommend or follow a particular hardware and software here. While dedicated film scanners (strip and sheet) will yield better results, a new generation of flatbed film scanner (for reflective as well as transmissive material, i.e., film) has changed the thinking on the need for a dedicated film scanner for film scanning. My choice is to work with a dedicated film scanner for 35mm and I use a flatbed for medium format.

It is a fairly simple matter to convert any color image to black and white, so you can scan color slides to color (RGB) or to black and white (grayscale) data. Most scanner software shares similar settings. You start with choosing the type of film then put in how you want the scanner to handle the film. You can scan at 16-bit grayscale, which pulls much more information than an 8-bit scan or even in color, and then convert later in software to grayscale. You then put in the “output” size, which is final print size, and also the resolution, usually 300 dpi. The software calculates the rest. Keep in mind that if you are scanning solely for black and white, choosing 48-bit color increases file size substantially.

Many scanners offer presets of various sorts, which you should test to see if they help or hinder your work. These vary from presets for film profiles, such as various types of slide and color negative films, to tone curve and color cast renditions, which can affect black and white conversions.

The mantra is “do not harm”; don’t add contrast, try to fix every exposure flaw etc in scanning. Get all the information you can from the film and then work the problems later in software. If you keep the tonal richness and detail of the original in your scan you allow the most leeway later in your image interpretation, or best chance for an faithful reproduction of the scene. It’s the same gospel as that of camera exposure. Even slides that have begun to lost dye integrity over time can be “salvaged”for black and white printing.

8 Scanning Tips

1) When scanning color negatives or slides you can scan for color or black and white. It’s easy to convert to black and white later in image editing software.

2) Scan at the highest bit depth available.

3) Test the dust and scratch removal software in your scanner to see if and when it causes unsharpness. It can help save retouching time later (except on black and white negatives and Kodachrome slides, on which it usually does not work.)

4) Scan for the highest non-interpolated resolution you think will be necessary. Do not resample in the scanner software. Never exceed the scanner’s optical resolution.

5) DO NO HARM. Do not try to enhance contrast too much or fix contrast or exposure problems; save that for the image editing software.

6) Watch for highlights. If necessary, do lower contrast in the scan phase. You are collecting information, and if you do not record the information in the scan you will not have it to work with later.

7) Think big, but be reasonable. There is a limit to how big a print you can make from various size format film. Test to see the limits of your scanner and don’t expect to solve all your problems in the scanner phase of things.

8) Scan neutral, create in software later for expressiveness.

Photos and text copyright 2010 George Schaub: Scanning can help preserve even faded or dye challenged slide film. This old Ektachrome slide was undergoing a magenta shift, but scanning it for b&w printing allowed the image to be useful again, and a nice print resulted.