Digital IR

In The 'Old Days'
In common with many photographers in this 'digital age', I spent my formative years using black & white film and darkroom-based techniques whilst also enjoying parallel activities with colour transparencies and audio-visual work. My darkroom-based work caused me to experiment with infrared film, notably Kodak High-Speed IR. I found the medium to be risky, wayward, constantly 'exciting' and hugely unpredictable. There was all the business of loading the camera in the dark (using a 'changing bag' on location), focusing, then, re-focusing to the 'red spot' on the lens, fitting the opaque filter to the lens and guessing the exposure. Then back in the darkroom the film was processed using one's preferred developer and, subject to the usual oddities encountered with IR, a number of usable negatives resulted. All this gave a certain mystique to the adventure of capturing images in IR.

The first photographs made by infrared radiation were made in the late 19th century with the first documented published infrared photograph in 1910 by Robert Williams Wood (1868-1955). Wood was an American physicist and professor of optical physics. He had been fascinated by what he called “invisible rays” and was credited with the discovery of electromagnetic radiation beyond the visible spectrum. He developed photographic emulsions to capture this radiation and produced the first photographs of both infrared and ultraviolet radiation. The photographs exhibit the characteristic whitening of healthy foliage which became known as the “Wood Effect” and it remains one of the distinctive features of many infrared pictures.

Infrared film for general use has been around since about the 1930's - indeed, television pioneer, John Logie Baird carried out experiments with an IR video system ('Noctovision'). The movie industry used IR to shoot 'day for night' to simulate moonlit scenes in black and white films. IR therefore has a long pedigree, the scientific community have long known of its properties as a recording medium for 'thermal imaging' and the like and 'serious photographers' have enjoyed its eerie and lyrical attributes for landscape work in particular. I certainly enjoyed the very special qualities of IR and when making the change to a digital camera system I realised that this was one aspect of film-based photography that I would very much miss. I looked forward to resuming infrared photography one day. That day did indeed arrive - and it's continued to evolve.

When we record the world using IR we 'reveal' how reflectivity from a variety of surfaces and objects differs from what we normally expect. For example, foliage and grasses become radiant and effervescent in appearance, whilst blue skies are presented near black and these special qualities lend themselves to pictorial expression. Naturally camera and lens manufacturers produce products to record 'visible light', however, 'in the good old days', there was a recognition by lens makers that an indicator of the focus point for IR would be useful, and the 'red dot' appeared upon lenses. Look for it on modern lenses and you'll be disappointed. The 'red dot' was necessary as IR 'light,' being at a longer wavelength, focused beyond the focal-plane of the camera and the lens required a 'tweak' to bring the scene back into sharpness.

White Balance
For best results, it's essential to make a pre-set 'white balance' for IR and your chosen specialist should be able to do this for you using a constant, calibrated light source apparatus. However should you wish to do it yourself it's is simple to do. Here's the basic procedure that you'll need to adapt for your model of camera.

Set the camera to measure the White Balance in sunlight
Point the camera to a patch of grass so that it completely fills the viewfinder
Seriously defocus the image
Measure / set the white balance (tip: You may need to under or over-expose for this test to gain a setting)
Save as a 'Custom Setting'
Make the 'Custom Setting' your normal 'White Balance'

Setting a custom white balance helps in presenting more meaningful information for the camera-based histogram. A custom white balance will typically provide a more evenly distributed channel-to-channel histogram for each of the three RGB channels and thereby, a more favourable tonal range for initial adjustments in 'RAW' and future image management.

RAW or JPEG?
I prefer to shoot with RAW files as they offer greater flexibility and control. However, if your camera permits simultaneous jpeg images to be recorded, then use the facility, as the standard rendering of the IR image by jpeg often gives a pleasing split-tone result. This is visible both when inspecting the image in-camera and as a 'thumbnail' via the computer file-browser and of course, in 'Lightroom' and 'Bridge' (ACR). This facility gives a useful indication about how the image could appear as a split-tone without 'Channel-Swapping'.

JPEG files can be used but offer less flexibility when we need to exploit the range of tones, some of which will frequently be 'off the scale' both for JPEG and the in-camera histogram display.

DI - IR Camera-Conversion Specialist:
More information about Advanced Camera Services can be found at:
www.advancedcameraservices.co.uk
or by 'phone: 01953 889324

When making contact with a member of the ACS technical or sales team, do mention my name.