Beyond the spectrum: An introduction to IR photography
My early attempts at infrared photography were always a bit of a struggle. I’d buy a roll of Kodak High Speed Infrared film to put through my Nikon, but because I never owned a proper infrared filter that would prevent visible light from reaching the film, my results were never as impressive as they might have been.
On those rare occasions when everything worked though, the images were spectacular; skin tones would fluoresce and foliage would appear white against inky black skies.
Kodak stopped making High Speed Infrared film about a decade ago but film users in Australia can still buy infrared sensitive films from Rollei and Ilford in both the 35mm and 120 film formats.
But infrared photography is not just limited to film cameras; digital cameras can also be used to make photographs with infrared (IR) and even ultraviolet (UV) light. But adapting a digital camera for use with IR and UV light is not as simple as loading in a film or adding a filter to your lens.
Removing the IR/UV Cut Filter
Digital camera sensors are inherently sensitive to visual, infrared and ultraviolet light, but because most photographers only ever want to make photographs with visual light, camera makers put an IR/UV cut filter in front of every sensor to stop the (usually invisible) rays of infrared or ultraviolet light from interfering with the ordinary colours.
So, if you want to explore infrared or ultraviolet light photography you first need to remove this IR/UV Cut filter. In the past some clever photographers have done this modification themselves, but given the complexities of modern cameras it is safer to have the IR/UV cut filter removed by a skilled camera technician. The modification typically costs a few hundred dollars for a full frame DSLR or mirrorless camera and this includes recalibration of the autofocus and metering systems.
The Full Spectrum
A full spectrum camera can be any ordinary digital camera that has the IR/UV cut filter removed. The camera becomes sensitive to infrared, visual and UV light and you decide which spectrum of light you want to work with by adding a filter to the front of the lens.
If you want to make photos with infrared light, you place an IR filter on your lens that excludes visual and UV light, and to make photos in the visual light spectrum you put an IR/UV Cut filter on the front of your lens. A 77mm IR filter can cost you about $150, while a 77mm IR/UV Cut filter can cost upwards of $250.
Working with ultraviolet light is a bit more challenging. To make photos outdoors with UV light you need an extremely rare and expensive UV Pass filter to block the visual and infrared light from reaching the sensor; the UV Pass filter used to make the UV photos for this story cost about $500 (for a 49mm filter) and slowed down the outdoor exposure times by a factor of seven stops!
A more practical way to make photos with UV light is to take a full spectrum camera into a darkened room and use UV lamps or LED based UV torches to illuminate your subject. These LED lights are very affordable but using them for extended periods of time is not good for your eyes without specific UV protection.
From an aesthetic perspective, photos made in the UV light spectrum can be rather boring, but for scientific and technical minded people the results can be fascinating. Various flowers and plants take on a different appearance under ultraviolet light, and luthiers and art dealers often use ultraviolet light photography to explore how old violins or artworks have been restored in the past.
It’s worth noting that there is a big difference between making photos in the UV light spectrum, and making photos of objects that fluoresce under UV light. Numerous objects including banknotes, white shirts, gemstones and even scorpions visually glow when illuminated with UV and this fluorescence can easily be seen by our eyes and photographed with an ordinary camera.
The Dedicated IR Camera
A full spectrum camera gives a photographer the option to explore both infrared and ultra violet, but it poses a problem too; both the IR Pass filters and UV Pass filters block visual light from entering the camera, and to compose and focus a photo you need to set up the camera on a tripod, compose the image, focus and then put the IR pass or UV pass filter onto the front of the lens to make the exposure. The process is rather slow and tedious, which is why many photographers prefer to have their camera modified to be a dedicated infrared camera.
In this modification the IR/UV cut filter is removed and then replaced with an IR pass filter that only permits infrared light to reach the sensor. Unlike the full spectrum camera, you can only ever use the infrared modified camera to make photos in the infrared spectrum, but this is perfect for most photographers keen on working in the infrared spectrum.
There are a some advantages in having an IR pass fitted to the sensor; the first is that you don’t need to put an expensive IR pass filter on your lenses, or have more than one of these filters if you work with various lens and filter sizes. Of even more benefit though, is that you can easily use almost any lens you own with for a dedicated IR camera, from fisheyes and extreme wide-angles (the ones you can’t normally put a filter in front of) through to extreme telephotos.
When it comes to fitting an infrared filter to your dedicated camera you will probably be asked what wavelength of infrared light you want the filter to be responsive to (see the Wavelengths and Light boxout). The options usually range from 580nm through 920nm but most people choose a 720nm filter which produces interesting infrared images in almost any conditions.
Compact, DSLR or Mirrorless?
Almost any camera can be modified for full spectrum, dedicated IR and even dedicated UV photography, from compact cameras through to DSLRs and even mirrorless cameras. Modifying a compact camera for IR photography can create a fun, go-anywhere camera that can make images unlike any iPhone, and the cost of the conversion is rather cheap.
Most people prefer to have one of their DSLR’s modified to be a dedicated IR camera, particularly a DSLR that they are about to replace with a newer model. The advantage of modifying a DSLR to be a dedicated infrared photography is that with an IR filter fitted over the sensor, the optical viewfinder performs exactly as it used to. Of course, if you want to preview what the image is going to look like in infrared, you need to switch on LiveView and look at the image on the camera’s rear LCD display. This can get annoying, particularly on a sunny day.
Now that Sony A7 series cameras have been about for a several years and many photographers are already upgrading their 3-year-old Nikon Z6 and Canon R cameras for newer models, getting one of your mirrorless cameras modified to be a dedicated infrared or even a full spectrum camera could also be a smarter option.
The big advantage in modifying a mirrorless camera is that as you look through the electronic viewfinder (EVF) you will see exactly how the photograph is going to look as an infrared image (or UV if you choose this modification).
Given that tonalities can appear dramatically different between visual light and infrared light (bright skies can go black, dark clothes can appear light, green foliage can appear white), being able to preview an image through an EVF can make the capture process a lot faster and easier.
What is true is that whether you choose to get a compact camera, a DSLR or even a mirrorless camera modified, making photographs in the infrared or even the ultraviolet spectrum is a lot easier than it ever used to be in the old film days, and the results can be just as impressive. ❂