What are extension tubes? In our latest Layman’s Guide we answer the common questions about this useful photo accessory and show the effects it can produce.
What are extension tubes?
Extension tubes are hollow tubes without any optical elements. Their purpose is to position the lens further away from the camera, to enable a closer focus distance.
How do they work?
The greater the distance between the lens and camera, the shorter the focus range will be. Longer extension tubes may therefore deny the ability to focus at long range.
The upside is that the maximum magnification factor of the lens is increased, so you can fill the frame with relatively small objects in close-up shooting.
What about compatibility?
Most popular camera manufacturers make their own extension tubes, but there are also a variety of independent makes available, like Kenko.
An important consideration for SLRs is that the electrical connections are maintained between the lens and the camera. Without these connections, autofocus will be impossible and you may not be able to govern the aperture of the lens. Instead you will be forced to shoot at the lens’s widest aperture.
How do I attach them to my SLR?
Extension tubes often come in sets, typically with three tubes of different lengths included (see left). These can be used individually or stacked for progressively greater magnification.
Remember, the greater the distance between the camera and lens, the less light will be transmitted from the scene to the camera. Longer exposure times are therefore required.
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