Photography Magazine

A telephoto lens is a lens which is considerably longer in focal length, compared to the ‘normal’ 50mm equivalent (on 35mm film cameras). When you use a long focal length lens, quite a few things happen - your depth of field becomes shallower (as seen in previous article), your images appear sharper as a result, the perspectives become flatter (background objects appear bigger than they do to the normal eye or the normal lens), and then you have a lot of technical mumbo jumbo to take care of as well. Lets look at some of that mumbo jumbo.

When you use a telephoto lens, your hands have to be that much steadier. This is thanks to the obvious reason that the longer the telephoto, or the focal lenght of the lens, the greater the dimensions of the lens, and the greater the difficulty of holding the thing steady. Simple physics tells us that the longer the ‘arm’ from the ‘fulcrum’, the more is the effect felt on the end of the arm when the fulcrum is disturbed. If you don’t understand that, no worries. It simply means, the longer the lens, the more chances you have of getting shaky pictures. The longest tele lens that you should brave hand-held would be the 300mm. Here is a rule to swear by - make sure your shutter speed is at least the inverse of the focal length. There is no hard and fast technical logic behind this, but it is simply a convenient way of determining a rough minimum shutter speed setting, as a mental note. For instance, if you are shooting on the 200mm setting of a zoom lens, you will need to have a minimum shutter speed of 1/200 sec. However you will in all probability still have a negligible amount of shake on your images, only visible to the trained eye, or on enlarged prints. To get a brilliantly sharp image, always use a tripod with your telephoto lenses. Some lenses are so heavy they need their own tripods.

This image of a homeless man was photographed in Bombay, using a tele lens. Notice that the sizes of the people’s legs behind him appear the same size as his own legs. This would not have been the case if the image was photographed on a wide angle lens. Moreover, a negligible amount of shake is visible, which means the image cannot really be enlarged to say more than 6×4. But of course it was a candid image, so the photographer had no time to set his camera on a tripod. Anyway, what is to be demonstrated by this image is the flattened perspectives of telephoto lenses.

To put things in a nutshell,

Tele lenses flatten perspectives

They gave shallow depth of fields

They need higher shutter speeds (to avoid shake) if hand-held

Very long focal length telephoto lenses are used for wildlife and sports photography

Extreme telephoto lenses are expensive and bulky!