|Sony Alpha telephoto prime lenses
Lenses with focal lengths above 50mm are commonly known as telephoto models. These fit less in, and are therefore ideal for getting closer to distant subjects or picking out detail; they also give a more flattering effect when taking photos of people. In contrast to wide-angle, lenses with longer focal lengths have an inherently smaller depth-of-field, which means it’s easier to get a blurred background effect – again ideal for portrait, wildlife and sports photography.
Good focal lengths for portraits are typically between 85mm and 135mm – these are often known as short telephotos. Appropriate focal lengths for sports or wildlife are generally much longer – at least 200mm, and ideally 300mm or more. Professional sports and wildlife photographers often use 600mm lenses, or even longer still. These are known as super-telephotos.
Lenses with smaller f-numbers gather more light thanks to their bigger apertures, which makes them better in dim conditions and for minimising the depth-of-field. Bigger apertures however mean a larger, heavier and more expensive lens.
As focal lengths increase, the risk of camera-shake becomes greater. Sony's Alpha DSLRs feature built-in anti-shake systems which allow you to handhold shots at slower than normal shutter speeds, but remember these won’t stop a moving subject from blurring, which brings many enthusiasts back to large aperture models.
As always, bear in mind any reduction in field due to your DSLRs sensor when choosing a lens. Sony’s APS-C models like the Alpha A200, A300, A350 and A700 have a reduction factor of 1.5x, which effectively multiply focal lengths by 1.5 times. So if you’re after a portrait lens with an equivalent focal length of 75 to 128mm, you’ll need a model with an actual focal length of around 50 to 85mm. Full-frame bodies like the A900 have no field-reduction factor, so an 85mm lens will deliver 85mm coverage.
Note: For a full explanation of lens specifications and examples of coverage at different focal lengths, check out our Camera Labs Lens Buyers Guide.