The wavelength of light is typically measured in manometers (nm) or 1 billionths of a meter. The spectrum of visible light for humans is approximately 400 to 700 nm and a standard digital camera or film will capture images in this range. The visible light spectrum falls between ultraviolet at shorter wavelengths and Infra-red at longer wavelengths. Infra-red images can be achieved either by the use of physical filters on a standard camera or by having the sensor on a digital camera modified to capture light in the Infra-red rather than the standard spectrum.
Using a modified digital camera is much more straightforward than using filters mainly because IR filters are extremely dense and accordingly it is difficult to view and frame the subject accurately. Typically this means framing the subject and then attaching the filter before taking the image. A further complication being that the focus of infra-red light is different than standard light and will confuse auto focus systems on a digital camera. For general use this is not such an in issue but where depth of field is critical it can and will be a significant issue.
On a modified DLSR this can be addressed by using a camera that has a “live view” display and using manual focusing whilst looking at the display as the display is exactly what is being seen by the sensor. The following images where taken with a 2nd hand Canon 40D fitted with a 650NM IR filter, this is towards the upper end of normal light and the beginning of infra-red so the resulting images are a combination of the two.
The 40D was selected because it is a reasonably modern camera with a decent specification / features including live view capability in order to address the focussing issue and is readily available 2nd hand, further being a Canon it is compatible with my existing lenses. Although earlier models (10/20/30D) are slightly cheaper they lack the live view capability and some manual adjustment is required to address the focussing issue.
I took advantage of a USA holiday to purchase the camera as prices are typically cheaper there, the camera was purchased from a professional dealer, Roberts Camera, via a popular internet auction site for $250 inc delivery and shipped direct to the specialist filter company who co-incidentally also charged $250 for the conversion and delivery. I chose to buy from the professional dealer as although it might have been slightly cheaper to win a private auction the dealer was offering a fixed price with 6 months warranty and even though it was unlikely I would be able to claim once back in the UK I thought it offered some reassurance as to the quality and condition of the camera and this indeed proved to be the case. In addition I thought the shipping service was likely to be more reliable than from a private individual as this exercise was time critical. So with thanks to Ebay, UPS Shipping (twice) and the excellent service from vendor Roberts Camera, Indianapolis and IR filter conversion by Kolari Vision, New Jersey the modified camera arrived at my hotel in Las Vegas in time for me to bring it home.
Incidentally the filter conversion company’s website, http://www.kolarivision.com, site has interesting information and tutorials on IR photography. The also provide some free automated Photoshop Actions for processing IR images, the standard action basically swapping Red and Blue channels to enhance the IR effect in the image. Although the actions are tailored for the filters they provide will work on any IR images. The images below have been cropped and straightened in Bridge and then processed using the Kolari Vision actions. The resulting jpeg’s were then resized, border added using the Faststone Image viewer batch conversion utility.
Some sample images below – more on the Infra-red gallery page – click here.
The left hand image show an image of flowering tree with standard camera and the right hand image is a similar scene shot with the IR modified camera. (Click on Images to enlarge).
Because the scene below of rushes in a canal bed is very predominately green the effect of post processing the IR results in an almost B&W image.
Infra-red gallery page – click here