Digital Infrared With A Converted Camera

Whilst all digital cameras are capable of taking an infrared image if an IR transmitting/visible light blocking filter is used, exposures will be long. Converting a digital camera for IR work solves this and other issues.

All photography in this article is by Wayne J. Cosshall. All rights reserved.

It is almost certain that any digital camera you have, whether a compact point and shoot, dSLR or expensive professional model, is capable of taking digital infrared pictures. This is because, whilst all modern digitals are fitted with an IR blocking filter, these filters are not completely IR blocking, allowing some through (see the various IR tests on the DIMi IR page). Thus all we need to do is place a visible light blocking/IR transmission filter, like the Hoya R72 or similar, over the lens and give enough exposure. The IR blocking filter varies in strength from camera to camera. This means that some cameras can just be used handheld, whilst most require a tripod and a full sun exposure of between a second and thirty seconds.

Unconverted 400D means long exposures and motion blur

The long exposures inherent to using a normal digital camera for IR produce a beauty of their own. Trees and grass blur in a breeze or wind, water smoothes out and people disappear from city streets. I love this effect myself. However, for some types of photography, these provide a huge limitation. You can’t easily shoot people, you are tied to a tripod (sometimes a good thing) and night IR photography becomes a distant wish.

A converted 350D means action photography is possible

The solution to all the problems with using an unconverted digital camera for infrared photography is to get it converted. Conversion involves removing the IR blocking filter and replacing it with one of your choice, or a clear glass substitute. A careful choice must be made here depending on the camera you are getting converted. Removing the IR blocking filter exposes the actual sensor and its full range of sensitivity (which extends from the ultra violet to the infrared).

The sensor can be left free to cover its whole range, in a conversion MaxMax calls an IR+Visible conversion. For compact cameras and the electronic viewfinder digital camera you get full autofocus functionality. With a dSLR you will only get autofocus working correctly over one band, usually visible. Many people interested in the conversion for astrophotography and other types of photography take this route, in which a clear piece of glass is inserted in place of the removed filter. Used with no filter you will get normal color images but may get some weird color effects at times due to the capture of UV and IR bands as well. To limit the band you place a filter over the lens. You can get filters to go on the lens that duplicate the characteristics of the old, built-in IR blocking filter or use visible light blocking filters that allow only the UV or IR parts of the spectrum to be imaged. For UV you will need special lenses, as normal glass blocks much of the UV. For IR your normal lenses will do. The only downside is that for IR-only work you must still use a visible light blocking filter, like the R72, on the lens. With a dSLR this will mean that you can no longer look through the viewfinder. With a non-SLR digital camera, such as a ZLR (electronic viewfinder camera or a compact) the choice is easier. Since autofocus is handled in a different way than in dSLRs, with compacts you can happily replace the IR blocking filter with clear glass and then use external filters to choose which part of the spectrum to use. With a separate visual viewfinder for framing, or with the live preview coming from the imaging sensor, you are free to frame your shots even with a visible light-blocking filter in place.

There is no need to stick to conventional IR subjects. Be creative

For those interested mainly in infrared work, an IR filter (blocking visible light and allowing through infrared), like the Hoya R72, can be inserted. This has the huge advantage of allowing you to see through the viewfinder of a dSLR whilst still shooting only in the infrared. The disadvantage is that you can no longer use the camera for normal, visible light photography.

Shooting people you know well, like my daughter shown here, is very disconcerting in IR, as their looks will change

The results of the conversion are certainly worth it. My 350D before conversion had exposure times in full sun of 1 second and f8 at 100ISO with a Hoya R72 filter. After conversion exposure times in similar lighting became 1/500 second at f8 and 100ISO. With some digital SLRs having full sun exposure times, unconverted, of 30 seconds at f2.8 and 100ISO, you can see the potential for improvement. Reduced exposure times mean reduced noise in the images too. Now I have the choice of handholding or not. So you need to decide what shooting is most important to you and thus the type of conversion that is required.

Another side effect of the conversion is to do with lenses. Before the conversion, I found some lenses created a hotspot when shooting with a Hoya R72 filter fitted for infrared photography. Since the conversion, I have found that these lenses do not create a hotspot. This makes sense. In the conversion, the so called hot filter, or infrared blocking filter, is removed. This filter is usually a dichloric filter, which means it reflects away the unwanted frequencies rather than absorbing them. In this case the reflection is straight into the back element of the lens, from where internal reflections can cause it to bounce back to the sensor, some of it getting through the filter (since none of the filters are completely IR blocking because we can do IR photography). Removing the blocking filter removes this strong source of IR reflection into the back of the lens.

There is yet another side effect of the conversion. On most digital came
ras the IR blocking filter is combined with the anti-moire filter, a filter that applies a slight
(or not so slight) blur to the light before it reaches the sensor to minimize aliasing effects. Removing the IR blocking filter removes the anti-moire filter as well. This produces images that are sharper unprocessed than before. The images seem to have a bit more snap and contrast to them, as well. The negative is that the camera can be more prone to moiré effects when shooting fabrics, wire mesh, etc.

So, after you have decided whether you want to modify a camera for much better infrared photography, and only you can answer that one, the next question is whether to make the conversion yourself or have someone else do it for you? There are web sites that offer you full instructions on how to do it yourself (links are on the infrared photography special page). There are also individuals and businesses that will do it for you (located with the other links). My 350D was converted by MaxMax.com and I am very happy with the result. The turn around was two days from receipt of the camera to it shipping out. Given the quality of the work, choice of filters to have emplaced and warrantee on their work, the conversion cost is not at all unreasonable, and I would not hesitate to use them for a future camera conversion.

My advice is to try infrared photography with an unconverted digital camera and something like a Hoya R72 filter, if you haven’t already done so. Push IR photography as far as you can with the gear you have. Then you will know whether you are really keen enough about IR to want a converted camera.

For me, a converted camera has been a huge joy. I am in love with infrared photography and adore the freedom that a converted dSLR gives me. You may too.