Infrared explained....... briefly

 

    First, a bit of technical stuff - I’ll try to keep it simple. As shown in the above diagram, visible light lies between the colors violet and red with a wavelength range between 400 to 750 nanometers. Slightly outside the visible red portion lies the large band of infrared with a wavelength range between 750 to 300,000 nanometers. Regardless of whether or not you know what wavelength is, I’m sure you can just look at the numbers and appreciate how vast the infrared spectrum is. Infrared photography - as you’ve seen on this site - deals only with what is called near infrared, meaning that this infrared light is very near to the visible spectrum. Those military night vision cameras that you see on TV, are taken with special cameras that capture mid-infrared (body heat), which is not possible with any of the consumer digital cameras on the market today.

    The image sensor in any consumer digital camera is inherently very capable of recording near infrared light along with the visible light. Manufacturers such as Hoya and B+W, make infrared filters which are designed to let infrared light through, and minimal to no visible light. These filters look almost completely black to the human eye simply because our brains don’t allow us to see infrared light.  So you would think the only thing you need to do is put one of these filters on your camera and you’d be good to go. Unfortunately that’s not the case. All digital cameras are designed to take standard color photographs. If the infrared light is allowed to hit the image sensor along with the visible light, it causes undesirable  aberrations (moiré and aliasing). Therefore, manufacturers place what is called a ‘low pass filter’ directly in front of the image sensor which blocks most, if not all of the infrared light. Some of the early point and shoot digital cameras (Nikon coolpix 950, Minolta dimage 7, and some Sony cameras) did not have a very effective low pass filter, so if you place an infrared filter ( such as a Hoya R72) on the lens,  you can very effectively take infrared pictures. Even these early cameras did block some of the infrared, so as a result your exposure times will increase dramatically, necessitating the use of a tripod. Nikon SLR models D100, D70, D70s and D40 are also capable of shooting infrared by just placing an infrared filter on the lens. Interestingly, some of the latest (from 2012 and on) have once again gone to weaker low pas filters so IR photography may be possible without any camera modification. The Fuji X-100, X-10 and Olympus OM-D are just a few. However with an unconverted conventional  DSLR, besides the long exposure times you will have to endure, the infrared pass filters are visibly opaque, you can’t see anything through the camera’s viewfinder..... a major inconvenience.

    A more practical solution to shooting in infrared is to convert a camera to shoot only in infrared. This is done by removing the low pass (infrared blocking) filter from inside the camera, and replacing it with an infrared pass filter. Once this is done you will no longer be able to take standard color images, but - and this is a big plus - now your exposure times will be pretty much the same as it was before the conversion, and, you can see through the lens because the infrared filter is inside the camera instead of on the lens. If you have an old digital camera lying around and want to have in converted, just Google “infrared conversion”, and you’ll find a plethora of sites that offer camera conversions. Neptune Photo also does infrared conversions at very reasonable prices to boot.  Most of the infrared images on my site were taken with a converted Nikon D100, but some were taken with a non-converted camera. I hope this helps you to understand this wonderful way to take pictures, a little better.