Using an IR Filter

Most cameras have an IR blocking filter in front of the sensor. In earlier DSLRs this wasn’t particularly efficient but it has been improved in most current models and mirrorless cameras but in the majority of cases they are still not 100% efficient so some IR wavelengths can get through, as long as you expose for long enough, writes Andrew James.

This means it is still possible to try your hand at IR photography without the need to convert a camera specifically for IR shooting. The results you get can be quite interesting, with that typical ‘frosty-white’ look to vegetation and blue skies going very dark black & moody. It’s a lot of fun. All that is required is a special screw-on IR filter on the front of your lens. For example, a Hoya R72 will do the trick nicely. When you put the Hoya R72 filter on it is blocking light up 720nm but it is at the wavelength above this that ‘interesting’ IR effects start happening.

How efficient the in-camera IR blocker actually is will vary from camera to camera, but with most cameras you’ll be able to recreate the classic monochrome infrared appearance when using a Hoya R72 filter. Of course, to get an image to record on the sensor you will need to increase your shutter speed quite considerably, even in bright and sunny conditions, which is when the filter will work at its best.

Using an R72 with my now ancient Canon EOS 5D Mk III I can get good results easily. Admittedly, it’s not as convenient as using an IR-converted camera because with that I can expose with almost no differences to a normal camera, except for the results of course. However, IR camera conversions are expensive and permanent, so are not for everyone. You have to be realistic about how much you’d actually use an IR-converted camera and judge that against the cost.

As you can see in the next image, the R72 filter is pretty much opaque. Hold it up to the sky and you won’t see anything through it!

If you are thinking of buying a Hoya R72 filter remember to check the filter size for your lens as you will be screwing it onto the front. The one I used was a 77 filter thread, which is typical of some wide angles and medium telephoto lenses. Typically, and depending on filter size, an R72 Filter will cost from about £100. Shop around for the best deal and don’t ignore a secondhand filter on eBay is my advice. They’re not as cheap as chips but they are a lot less expensive than having a camera converted.

How to use it
The best way to show you the type of result is with some example images. Below is a scene photographed normally, without any filtration. Not exactly an award-winning image but it works as an illustration. I manually focused on the tree, set an aperture of f/8 (using ISO 100) and this required a shutter speed of 1/250sec in the bright conditions to give me the right exposure.

With the camera in exactly the same position on a tripod and focus unchanged I put the Hoya R72 on the front of the lens. I screwed it on carefully so I didn’t alter the focus, switched on Live View and changed the shutter speed (working in manual) until I could see an image appearing on the screen. In this case it happened to be at 6 seconds! Using a cable release I fired the shutter and the result is the next image – the raw  ‘red’ scene.

As I had chosen to shoot raw, I then simply brought the raw file into Lightroom and opened it in the Develop module.  The Lightroom conversion was easy. Just hit V on the keyboard to convert to Black & White and then tweak to your heart’s content. There are no rights and wrongs here, just move the different ‘colour’ channels in the black & white panel to work out the look you want. You’ll find the red and orange sliders have the most impact on vegetation.

In my opinion, the external IR Filter doesn’t give you such intense whites as a converted IR camera can, but it does provide a cheaper solution to the IR look and with careful choice of shooting conditions and some interesting scenes you’ll soon be able to build up a portfolio of moody IR black & white images.