The World of Digital Infrared Photography

The World of Digital Infrared Photography

I will start this article with explaining the title; I know that infrared photography has been around for a very long time using film. But I have never tried or used this media so I can only give my infrared experiences using digital cameras.

What is Infrared ?

As far as we need to know concerning photography there are three main light sources, these are Ultraviolet, Visible Light and Infrared.
The first one being Ultraviolet, these are mainly used as X-rays and have wavelengths of up to 400 nanometres.
Then we have Visible Light, obviously that is where all our normal photography is done, and these wavelengths are between 400 and 700 nanometres.
Finally we have Infrared, now infrared has a very wide range of waves ranging from approx 700 to 1,000,000 nanometres. This wide range has been broken down into sections known as ‘near infrared’ ‘mid infrared’ ‘far infrared’ ‘ and ‘thermal infrared’.
Now when a lot of people think of infrared, they always seem to think of heat seeking images that we see on TV from police helicopters, well they are recording ‘thermal infrared’.
What we are interested in is ‘near infrared’ which is only just outside the visible light spectrum, near infrared has a wavelength of about 700 – 1200 nanometres.

Below Diagram showing relationship between the various wavelengths

Why use Infrared ?

Infrared images have a totally different look to them.
You get good Infrared images around midday while the lighting is not good for visible light images, although Infrared light appears to be stronger in morning and late afternoon.
If you overexpose on a wet cloudy overcast day, the results can give a much better effect to that day.

Above Colour Visible Light Image and Colour Infrared Image

Below Infrared will also see through haze, giving clear view of background

Above Colour Visible Light Image and Monochrome Infrared Image

How a Filter works ?

All filters work roughly the same, like say a ‘Green’ filter – A green filter does NOT turn everything green it just blocks out all other colour wavelengths from passing through depending upon what strength that that particular green filter is rated at.
A infrared filter works just the same by blocking visible and ultra violet light.
A lighter infrared filter will allow some visible light through and is more suitable for colour infrared photography.
A medium filter works well for monochrome photography.
While a dark filter will give very dramatic monochrome images.
Below is a indication of the infrared numbering system.

What IR Filter can I use ?

There are lots of different IR filters to chose from all having different numbers, these numbers indicate the density of the filter itself and just how much visible light it will block.
When using a Infrared filter, make sure that no visible light can get in between the filter and lens, like the Cokin or Lee filter system as this can cause glare on the final image.
It is best to use some sort of screw in filter or fix a Cokin type filter to a suitable screw in adaptor.

Above This is the Cokin version, where if you use the supplied filter holder visible light will get in between filter and lens causing glare. To overcome this I stick the adaptor ring straight onto the filter using double sided tape.

Above This is my home made Infrared filter using and a Cokin screw in adaptor which has been taped to the filter.

What Camera can I use ?

Most digital cameras will take infrared images, but some are better than others. This is due to the internal sensor filter, which is designed to cut out infrared waves which are unwanted for visible light photography.
To test if your camera can take Infrared then try this simple test.
Set your camera to Manual exposure, use a wide aperture approx f3.5, set shutter speed to about 5 seconds and manual focus to about 1 metre.
Mount you camera on a tripod in a darkened room.
Set self timer or use remote shutter release.
Then press shutter or use remote shutter release.
When shutter opens, point and press any TV remote at camera and move it around.
Check camera LCD preview screen for results, hopefully you will see a line of dots – this is because a TV remote will keep sending out a signal as pulses whilst you have your finger on the button.
If you only get a faint image, then try increasing the ISO.

Above This is what you should see on your camera preview screen if your camera can record Infrared Images.

Taking your First Shot

You will need to choose a bright day without too much wind as we will be using long exposures, so any movement of trees / foliage will appear blurred.
First thing is to compose your shot, a suitable subject would include a tree in leave (which should appear white as these leaves reflect a lot of infrared wavelengths) and some sort of man made structure (which should appear darker as this will not reflect so much infrared wavelengths).
Next you will need to mount the camera on a tripod, then before fitting a infrared filter you will need to compose and focus your shot ( this is because your camera will struggle to focus through a Infrared filter ) and then turn the auto focus off.
You are now ready to fit your filter.
Now you need to set the camera to manual exposure mode.
The next settings will vary depending upon available light and subject matter, but as a starter try these first.
Set aperture as wide as your lens will allow, something light f2.8 or f3.5.
Next set shutter speed to about 2 seconds.
Then set self timer or use shutter cable release cable so that you do not move the camera whilst taking the shot.
Leave ISO at a low setting for now, something like 100 or 200 ISO.
As you are probably taking a landscape image make sure that you are using matrix metering for the whole scene.
Remember to keep viewfinder covered so that no stray light enters through viewfinder while the shutter is open.
Now take the picture, and hope.
You will see straight away if you managed to capture a image, plus if it is too dark or too bright, and from here you can make further adjustments for your next shot.
If image is too dark, then try using a longer shutter speed.
If image is too light, then I would go for a smaller aperture, so that more of your image will be in focus.
After a few more shots you should start to get a image that is looking somewhere near rightly exposed.
Now you can start to use the histogram to get exposure spot on, and you will probably find that you need to over expose slightly for best results.

Finally, hopefully you will have some fun experimenting with this media and if you find this Article interesting then I can produce more explaining advance techniques including focusing, correcting white balance, using a dedicated Infrared camera plus improving your infrared images in Photoshop.