Infrared Photography: The Invisible Light
Infrared – it surrounds us every single day of the year but we cannot see it. However with a little bit of foresight and preparation we can photograph it, and choosing to capture infrared images opens up a new world of photographic opportunities. But before we can start to photograph in infrared, it helps to have a basic understanding of what is actually is. Essentially, infrared light is invisible radiant energy with longer wavelengths than normal light and extends just pass the red edge of our visible spectrum. These wavelengths are measured in nanometers (nm), with infrared light being present from around 700 nm.
Infrared Photography in the Past
Whilst shooting in infrared may sound very technical, and almost a bit geeky, I am pleased to say that the process is actually quite simple nowadays. However, it has not always been that way. Back in the days of film, when I first started shooting infrared, the process of using IR was a complicated and time-consuming process. First of all, the film had to be loaded into the camera in complete darkness (the light seals of the film canisters did not block infrared light), then the images had to be composed using visible light and the only way to focus was by using an basic infrared scale on your lens (the reason for this being that infrared light focuses at a different wavelength compared to visible).
Next, before fitting a visually opaque filter (which only allows infrared light to pass) I had to take a meter reading based on visible light and then try to compensate for removal of visible light (i.e. estimate the exposure required for infrared light, which happened to be a difference of between three to six f-stops). Once the filter was fitted I would take a shot (or more accurately a few shots bracketed at different exposures) and then restart the process again for the next shot.
Finally, the film was unloaded in complete darkness and sent to a lab that could guarantee to also unload the film in darkness and also convince me that they would only use metal film processing tanks as opposed to plastic (plastic will not entirely stop infrared light). I have shot hundreds of images this way – in fact, I was still using film until last year. But digital infrared is so much easier and so much more fun!
Modern-day Infrared Photography
There are two ways to digitally shoot infrared, either by using a normal DSLR with a Hoya R72 filter (or equivalent) or by using a camera specifically converted to just capture infrared. There are pros and cons to both methods. If you go for the unconverted DSLR & filter route, you will find that the use of a tripod is essential. All modern cameras are fitted with an infrared blocking filter. By using an external R72 filter you are effectively blocking visible light so that only infrared light is passed through to the sensor. As the factory-fitted filter within the camera is designed to block infrared light, the time required for exposure is greatly increased. This is not dissimilar to how a cheap 10x ND filter works. But the advantage is that you still have a camera that can be used for other purposes.
Conversely, a converted camera (which has had the infrared blocking filter replaced with a visible light blocking filter) can be used handheld, as the exposure times are similar to visible light. However, it can no longer be used for shooting visible light.
If you have never tried infrared photography before, I would strongly recommend that you try using your current camera fitted with an infrared filter before either buying a converted camera or having an old camera converted.
In the Field
Enough of the science – it is time to talk photography. Common wisdom is that you should shoot infrared images around midday, on a bright sunny day in the summer. Nonsense. Infrared is visible all year round, and whilst it is true that it is stronger in the summer (as is visible light), there is absolutely no reason why you cannot shoot on a mid-winter day. As for the need for a bright sunny day, the same logic applies. Infrared will still be present on an overcast day, but it will be softer as it is being diffused by the clouds – just like what happens with visible light.
Of course there are some advantages to shooting infrared during the summer but these are more to do with the natural conditions as opposed to the light. The spring and summer months are of course the period when the landscape springs into life with new leaves and shoots on trees and alike. Plus, clear skies and trees is a winning infrared combination. Contrary to popular belief, trees (and other plants) do not actually radiate infrared but in fact reflect it. I am sure that you are starting to see a pattern here – infrared light is not that dissimilar to visible light.
Regardless of whether you are shooing with a converted or unconverted DSLR, there is no avoiding the fact that infrared light focuses at a different wavelength to visible light. As the AF system of your DSLR has been calibrated to focus via visible light, you will find that you infrared images are slightly out of focus. There are two ways to combat this, either by using a fairly small aperture to increase your depth of field or by utilising the live view function of your camera. When you use the live view mode of your camera, the AF generally works on a contrast-based system, meaning your camera focuses by evaluating the actual image reaching your sensor. This is one reason why a mirrorless camera can make an excellent choice for infrared conversion.
Why Shoot in Infrared?
As you can see there is a certain degree of science behind shooting in infrared and you may be starting to wonder what the actual attraction is of photographing it. In many ways, infrared photography is unlike another other genre of popular photography. Whilst I have seen examples of people shooting portraits and wildlife using infrared light, there is no denying that landscapes are the classic subject for infrared photography. Whilst I tend to concentrate on monochrome infrared photography, over the last few years we have seen a sudden surge in people shooting infrared in (false) colour. This is unquestionably due to the infrared capabilities of digital cameras – colour infrared film has not been manufactured for years and even then it did not allow you to achieve the false colour look of glowing white trees against a blue backdrop of a clear summer sky.
What ever your preferred kind of infrared photograph is, it is advisable to shoot your images in raw format as the post processing of infrared images is just as important as the actual capture.