Bellows and bellows lenses

For more convenience and even closer focusing a bellows unit can be placed between a camera and lens. a bellows acts like a variable extension tube. Instead of switching and recombining various tubes to get the desired size, you simply turn a knob to expand or compress the bellows. In this way you obtain exactly the right length needed, and you do not have to settle for a tube combination that merely comes close.

Some bellows units have built in scales that show lens extension and magnification ratios for several focal lengths – usually the normal 50mm and two or three others. Theses scales are mainly used to help calculate the necessary additional exposure if your camera doesn’t have through the lens metering.

Like extension tubes, bellows units come in both manual and automatic versions, the latter retaining all the automatic exposure functions of camera and lens when you use a double cable release. Some units have just one track (or set of tracks) used only to support the bellows and to set the desired length. More expensive units have an additional set of tracks (or some similar device) to allow the camera/bellows/lens assembly to be shifted as a whole for easier focusing at very close distances.

However, the thickness of a bellows prevents an ordinary lens from being racked all the way back to its infinity position, the farthest point of focus is quite near even when the bellows is compressed all the way, and it is closer still when the bellows is extended. The particular range depends upon the focal length of the lens. There is, however, a special optic called a bellow lens which has a much greater focusing range because it come s in a short mount. That is, the total length of the mount is much shorter than the focal length of the lens. When the bellows is compressed all the way, the total thickness of camera, bellows and mount does not exceed the lens focal length. Therefore, this kind of lens can be focused from infinity all the way down to fractions of an inch. (This is true when all components are from the same manufacturer, but may not be true otherwise.) Furthermore, short mount bellows lenses are usually macros, which means they are designed to work best close up. However, any lens on a bellows can get you into the true macro range, defined as the range where magnifications start at full life size and get bigger from there.


More about close up lenses

- Supplementary close up lenses
- extension tubes
- macro lenses
- hints for close up photography
- tips for using close up magnification