BEYOND THE RAINBOW: INFRARED PHOTOGRAPHY, PART TWO
In this second instalment, Hans Weichselbaum explores the phenomenon of infrared photography, digging deeper and discovering just what infrared photography does with ‘normal’ colours
In this second instalment, Hans Weichselbaum digs deeper into the phenomenon of infrared photography
In the first part of this series, we looked at some practical infrared photography using a modified camera. In this second part, we’ll explore the possibilities a bit further, and find out what infrared does to all our familiar rainbow colours. Dedicated infrared photography doesn’t come cheap, so we’ll also look at how you can simulate a genuine infrared image by starting from a normal, everyday shot. People have always been fascinated by the world of the invisible. The visible rainbow spectrum is only a tiny sliver of the entire electromagnetic spectrum, stretching from X-rays to radio waves. In Image 2, you can see the part of the spectrum coming from the sun that is important to us photographers:
The ultraviolet region is not very interesting to photography, unless you want to see the
world through the eyes of a bee. This band is well blocked out by the filter in front of your sensor. If you want to dabble in ultraviolet photography, you need to remove this filter. Secondly, you need a (very expensive) quartz glass lens — and then you’ll find there is not much ultraviolet around anyway, because the atmosphere filters out most of the ultraviolet from the sun.
So, we are basically left with the infrared region to explore. Keep in mind that more than half of the sun’s radiation reaches us in the form of infrared — there’s a lot of infrared around!
Image 2 also shows you the near-infrared band that’s interesting for us photographers, stretching from about 700nm to 1000nm. Beyond that comes the far-infrared radiation band — the region used for thermal photography, which is not shown in this diagram.
Infrared photography literally opens up a whole new world, because it’s a world of the unseen. If you are into fine-art photography, you should have a serious look at infrared. It will make your landscape photography stand out, but it also works for portrait and wedding photography.
The quickest, easiest, and least expensive way of getting into infrared photography is to use an infrared filter on your lens — assuming that you can fit a filter on your lens. The ultraviolet filter that you put on your lens blocks out the ultraviolet, and you might be forgiven for thinking that an infrared filter does the same, blocking out the infrared part of the spectrum. However, it’s the opposite.
Infrared filters are transparent to infrared and block out the visible light spectrum! It’s a bit confusing, but once you get your head around the concept, it makes sense. You don’t want to capture the visible rainbow colours, but only the infrared spectrum that’s reflected from your subject.
Image 3 shows you an R72 filter, which blocks out the visible spectrum with a cut-off around 720nm. Image 4 depicts the transmission characteristics of a number of infrared filters. You can see that all of them have zero per cent transmission for light below about 700nm. These filters are really black — but never use them to look directly into the sun. The infrared light that gets through the filter will damage your eye!
All digital sensors are very sensitive to infrared, and you might think that putting an infrared filter on your lens will do the trick. Even though it does work, all cameras also have an infrared block filter mounted in front of the sensor. There is always some infrared light trickling through, but very little. This means that you have to push the ISO really hard and still need exposure times that run into seconds, even in plain sunlight. For ordinary photography, you’ll need a camera that has been specially modified for infrared.
Most infrared photographs are black and white, although you can bring in some colour if you go for a filter with a cut-off below 700nm. The obvious question that comes to mind is: how does infrared photography represent our familiar rainbow spectrum on a white-to-black greyscale?
I went to great lengths to find this out by taking shots of a colour chart under infrared. However, this exercise is not really useful because it all depends on the material the colours are printed on, not so much the colours themselves. If the material is reflective to infrared, it will show up as light grey or white. A good example is my photography bag, which is fairly black in ordinary light, but comes out as white under infrared (see Image 5). The manufacturer obviously used a material that reflects infrared, otherwise my camera gear would cook in the sun. I assume that the bag could have been tinted blue or red and would still have shown up as white under infrared.
What immediately sets most infrared photos apart from normal black-and-white shots is that green vegetation comes out as very light. Green plants reflect infrared, producing the so-called wood effect. The contrast was very obvious when I put a leaf on the matching green colour patch of a colour chart (see Images 6 and 7). However, the green patch on the colour chart could have turned out lighter or darker under infrared, depending on the material used.
Another interesting characteristic of infrared light is its ability to smooth out skin tones. That’s why portrait and wedding photographers love to work with infrared. You get a milky smooth skin, and all the freckles are gone. The eyes can get too dark and overemphasized, so some post-processing might be necessary.
My shot of Brooke was perfect straight out of the camera (see Image 8). Her skin was smooth to start with and the infrared light couldn’t really show off its ability to get rid of skin imperfections. Her blue eyes didn’t need any post-processing, either, but you do need to watch out if your model has very dark eyes. Incidentally, photographing under ultraviolet light does the opposite — it accentuates skin imperfections and will show freckles that aren’t even visible in normal light.
The best time of day for infrared photography is midday under full sun. Ideally, you should have a clear sky with some clouds for effect. Overcast skies often leave things looking flat without enough contrast, although you might prefer that for portrait shots. A cloudless sky often looks like a vast black void and isn’t very
interesting. A few clouds come in handy for infrared photography.
Infrared simulation with Photoshop
If your camera is not suitable for infrared photography, or if you’re waiting for a new infrared filter to arrive, why not try to simulate the effect in Photoshop? Do keep in mind that infrared photography captures subtle tonalities that don’t show up in a shot taken in daylight. No amount of digital editing can retrieve these nuances, but we can get a reasonably good approximation to the real thing.
The key tool for transforming a colour photo into an infrared black-and-white simulation is Photoshop’s Channel Mixer. The idea is to take the green channel to the maximum 200 per cent, and reduce both the red and blue channels to compensate.
• Make a duplicate layer. This is not strictly necessary if you work with adjustment layers, but it’s always handy if a mistake slips in. • Open the Channel Mixer from the adjustments panel, or go to Adjustments > Channel Mixer. Choose the black-andwhite infrared preset and you will see the green channel slider jumping to its maximum setting of 200 per cent (see Image 10). The optimal settings for the other two channels will depend on your particular image, but the percentages should add up to around 100 per cent. The Constant slider allows you to fix the overall tonality. Don’t forget to check the Monochrome box. • Make the image layer active again by clicking on it. Then select the green channel in the channel palette and add Gaussian blur (radius around five pixels). • Go straight to Edit > Fade, reduce the opacity to 30 per cent, and set the blending mode to Overlay. Also try blending in screen mode. This will give the green channel the typical luminous glow. • Click on RGB in the channel palette, then
return to the layer palette. • Noise can be added to simulate film grain. I like to insert a hue/saturation adjustment layer between the Channel Mixer and the image layer to have more control over the tonalities of the various colours, e.g. blue often needs to come out darker.
This is a simple recipe that can be made into an action. You can go a step further and prepare separate selections, e.g. a selection for the vegetation and another one for the sky, and then work on them individually. This will give you superior results, but it is time-consuming and does not lend itself to a simple action.
See my result of the infrared simulation in Image 11, and compare it with the genuine infrared photography seen in Image 12. The characteristic glow of the real thing is missing in the simulation. There was an overcast sky, so the typical black sky wasn’t there, either.
The Lightroom enthusiast will find a preset in the Develop module called Infrared. This is a good starting point for any further colour tweaking for best result. If you have the Nik Software plug-in, which you can download free, you’ll find an Infrared Film preset in the Color Efex module. After selecting the filter, the software gives you tons of additional controls to tweak brightness, contrast, shadows, and highlights.
I hope that this in-depth introduction to infrared photography will encourage you to have a serious look at digital infrared photography. A simple infrared filter on your lens, plus a tripod, can get you started. If you like the results, you might consider getting one of your old redundant cameras converted into a dedicated infrared shooter. I can highly recommend Kolari Vision (kolarivision.com), if you are seriously thinking of getting into infrared photography.
IMAGE 1 — AUCKLAND DOMAIN IN INFRARED LIGHT
Hans Weichselbaum has been on the digital-imaging scene since Photoshop 3 in 1994. He has shared his expertise in workshops countrywide and in articles for three different publications.
Hans is a perfectionist and passionate about photography. His background in science and philosophy lets him look outside the box when problem-solving. His business specializes in Photoshop tuition, highquality film scanning, largeformat printing, and colour calibration.
IMAGE 2 — THE SUN’S SPECTRUM THAT IS USEFUL FOR PHOTOGRAPHY
IMAGE 4 — TRANSMISSION CHARACTERISTICS OF SOME INFRARED FILTERS
IMAGE 5 — A BLACK CAMERA BAG UNDER INFRARED
IMAGE 3 — AN INFRARED FILTER
IMAGE 8 — INFRARED PORTRAIT
IMAGE 6 — A GREEN LEAF UNDER NORMAL LIGHT
IMAGE 7 — A GREEN LEAF UNDER INFRARED
IMAGE 9 — GARDEN IN NORMAL LIGHT
IMAGE 10 — THE CHANNEL MIXER FOR INFRARED SIMULATION
IMAGE 12 — GARDEN SHOT WITH INFRARED-MODIFIED CAMERA
IMAGE 11 — GARDEN IN SIMULATED INFRARED