Infrared Photography

A Brief Introduction to the Fascinating World of Infrared Photography

Infrared photography has given a new dimension to the field of photography and imaging. It comes across as a wonderful photography technique that makes apparent, the interesting nature of light.
What's beyond the red end of a rainbow? It is infrared. Have you imagined using this portion of the light spectrum for photography? Well, I had never thought about it before I came to know about this interesting and unusual photography technique, infrared photography. How is the technique implemented? Does it need any special equipment? How is it different from conventional photography? Let us find out.

Infrared photography makes use of an image sensor that is sensitive to infrared light. This technique uses the near-infrared part of the electromagnetic spectrum. Cameras used for this type of photography are equipped with an infrared filter that lets infrared light pass through the camera, while blocking the visible light spectrum. Most of the single-lens reflex (SLR) camera lenses have a red dot or line, referred to as the infrared index mark that is used for focusing. Many of the modern-day cameras with infrared capabilities come with autofocus lenses that do not require manual focusing. Some of them have apochromatic lenses fitted into them, which do not need to be focused for the infrared spectrum. Their optical design enables them to automatically focus into the near-infrared region of the electromagnetic spectrum.

Digital cameras are sensitive to infrared radiation, due to which colors seem to appear unnatural. However, digital cameras of the present times have in-built filters to remove the IR sensitivity. If the IR-blocking filter in digital cameras is replaced with an IR-passing filter, the camera can be used for infrared photography.

Black-and-white infrared negative films are sensitive to wavelengths between 700 and 900 nm and many of them are sensitive to blue light. Black-and-white photography is mostly done using an orange, red, or an opaque filter over the lens, as it blocks exposure to blue light. The purpose of using filters is to block the visible blue wavelengths and allow infrared light to pass. Orange or red filters allow a very small amount of blue light to reach the film; dark red filters block almost all the blue wavelengths whereas the visually opaque ones block the blue wavelengths as well as the visible red light, so as to allow pure infrared photography. Color infrared transparency films have three sensitized layers that translate infrared to red, red to green, and green to blue, during the reproduction of images. Color infrared does not require to be focused to the infrared index mark on the camera lens.

Infrared photography is interesting. It can achieve the production of differently colored images, thus adding to the excitement involved in this type of photography. You will be surprised to see green leaves appear white and the blue skies appear black, in images captured through infrared cameras. Why does foliage appear white? It is because leaves reflect a large amount of infrared energy rather than absorbing it. Also, chlorophyll fluorescence contributes to the brightness of infrared photographs. The glow seen in these photographs of leaves is attributed to the structure of living cells, making the leaves shine on being exposed to infrared light. The glow is referred to as the 'Wood effect', in honor of R.W. Wood, an eminent name in the field of infrared technology. With infrared photography, clouds appear white or black and water bodies appear like huge reflective surfaces. Generally, reds, whites, and greens appear light while blues, browns, and dark greens in shadow appear dark. If you try photographing human figures, you will find that their eyes look strangely black and surreal and their skin appears to glow.

Infrared cameras are commonly believed to record heat, as heat output is a form of infrared radiation. However, it is untrue that infrared cameras can detect heat. Rather, infrared films record certain wavelengths of infrared light emitted by infrared energy sources. IR photography is the technique of recording infrared energy that is reflected from objects and not that which is emitted by them. This also explains why you cannot practice IR photography in the dark (i.e. in the total absence of light).

  • The first step in this type of photography is to focus on the object whose image is to be taken. Then place an infrared filter in front of the camera lens. Now, adjust the exposure and take the shot.
  • The exposure time needed for infrared cameras is longer than that required in conventional photography. So, use a tripod for composition and focus prior to capturing the images.
  • Photographing the moving waters is advisable only if your camera has a long exposure time as it gives a smoothing effect to the pictures.
  • For obtaining a sharp photograph, use a tripod, a narrow aperture, and a slow shutter speed that does not compensate on the focus. However, irrespective of the width of the aperture, it is necessary to refocus the camera lens exactly on the infrared index mark.
  • Only practice and experience can make you a good infrared photographer. If you are patient in practicing, you will keep getting better.
Infrared photography makes the world look different from what it actually is. Very few things in the world can do this. Explore this fascinating field of photography and share your experiences with us.