Infrared Photography

In infrared photography, the image sensor or film used is sensitive to infrared light. This is the part of the light spectrum referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging and is primarily used by the police, military & filmmakers recording nocturnal animals. Wavelengths used for photography range from about 700 nm to about 900 nm. Usually an “infrared filter” is used; this lets infrared (IR) light pass through to the camera but blocks all or most of the visible light spectrum (and thus looks black or deep red).

When these filters are used together with an infrared-sensitive sensor, very interesting effects can be obtained; black-and-white images with a dreamlike appearance, infrared images are also very kind to people as they will tend to record the light reflected from a millimetre or so under the skin and will consequently ignore blemishes and fine wrinkles.

The effect is mainly caused by foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow. Chlorophyll is transparent at these wavelengths and so does not block this reflectance. There is a small contribution from chlorophyll fluorescence, but this is extremely small and is not the real cause of the brightness seen in infrared photographs.

The other attributes of infrared photographs include very dark skies and penetration of atmospheric haze. The dark skies, in turn, result in less infrared light in shadows and dark reflections of those skies from water, and clouds will stand out strongly.

Because most cameras are designed to record light in the visible range they are not particularly sensitive to infrared, to record a satisfactory image much longer exposure times are required – 25-30 seconds in not unusual, so landscapes are by far the best subject to choose

Normal/Visible Light	Image taken with IR Filter	Infrared Image

Panoramic Photography

Shortly after the invention of photography in 1839, the desire to show overviews of cities and landscapes prompted photographers to create panoramas. Early panoramas were made by placing two or more plate’s side-by-side. The first commercially available photographic process used silver coated copper plates to produce highly detailed images.

Things have moved on considerably since then. With digital photography the images can be “Stitched” together using many different software packages. Some of these do all of the aligning, cropping and blending, while others will only handle some of the process allowing the photographer to use his skills to the full.

When taking a series of images intended for use in a Panorama it is usual to use a tripod to ensure the images are correctly aligned horizontally and will be taken with a 20-50% overlap. There is however a problem called parallax to deal with.

What is Parallax?

Parallax causes adjacent pictures for a panorama to differ in ways that prevents them from being stitched together perfectly. It can cause ghosting, blurring, or even prevent stitching software from being able to work out where to position the pictures to be able to stitch them together.

It’s really easy to see the effect of parallax: Hold up your index finger in front of you at arms length. Close one eye and line up your finger with something a little distance from you such as a door or a piece of furniture. Now without moving your finger, open the eye that was closed and close the eye that was open – your finger will seem to move slightly. This effect is known as parallax. To find out more follow this link to Wikipedia.

Exactly the same happens when you shoot pictures with your camera when using a tripod on its own. To overcome parallax we have to rotate the camera around the Nodal Point – this is the point inside a lens where light paths cross before being focused onto the digital imaging device or film. A number of photographic equipment manufacturers produce specialist panoramic heads. These allow the camera to be moved in relation to the point of rotation, for a good quality one you can pay £200-300 plus…

With a little ingenuity though, a device can be easily constructed for a fraction of the price. Using a Manfrotto Micro positioning plate with the camera in the landscape position. This has produced very acceptable results, but the image is rather narrow.

I have now added a bracket that allows me flip the camera in to the portrait position. I now get a taller panorama, but this does require more images – 10-12 instead of 6-8.

Manfrotto Micro positioning plate

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