Buying A Lens - What You Need To Know

There is a large selection of lenses available for SLR cameras nowadays. You can choose from fixed focal lengths, zooms, superzooms and macro lenses but how do you choose the right lens and what do all the different designations that lenses have mean? This article will help know what to look for and explain some of the jargon out there.

DIFFERENT LENS TYPES:

Macro lenses:

A true macro lens lets you get in close enough to your subject to reproduce it at life or half life size. Macro lenses come in a variety of focal lengths (usually between 50mm and 200mm) and the vast majority are a fixed focal length (not zooms).

Fixed focal length lenses:

Fixed focal length lenses are the ultimate in image quality as they have no moving optics as in a zoom lens. Fixed focal length lenses generally have wider maximum apertures so are perfect when shooting in low light. Big fixed focal length telephoto lenses are a popular item in the wildlife or sports photographers equipment list.

Zoom lenses:

The majority of lenses sold today are zoom lenses. A zoom lens has an adjustable focal length which makes them more versatile but the image quality isnt as good as a fixed focal length lens. A new digital SLR is most likely to come with a standard zoom lens (something like a 18-55 or 18-70). If you want a wider angle view (to get more of your subject into frame) then you need a smaller number, eg 10-20 / 12-24. If you subject is at a distance and you want to make it appear closer then you need a telephoto zoom. These are especially useful when photographing sports or wildlife and will have a larger focal length, eg 70-300 / 100-400. Telephoto lenses will magnify camera shake however so it may be worth investing in a lens with a built in image stabiliser.

JARGON BUSTER:

AL (Pentax) - This stands for aspherical lens which refers to the optical elements within the lens. It will offer improved performance and a reduction in the number of component lenses requires therefore giving you a more compact lens.

APO (Sigma) - An APO lens has Apochromatic lens elements made from special low dispersion (SLD) glass which produces sharper images and helps to reduce colour aberrations.

DC (Sigma) - Sigma DC lenses have been designed to work with digital SLR cameras with an APS-C sized sensor so are not compatible with 35mm or full frame digital SLR cameras. Because an APS-C sized sensor is smaller than a full frame sensor these lenses are more compact and lighter in weight than the equivalent which is suitable for all camera types.

DG (Sigma) - Sigma DG lenses are designed for use with both 35mm or digital SLR cameras (full frame or APS-C sized sensors).

Di (Tamron) - Tamron lenses which are suitable for both 35mm or digital SLR cameras (full frame or APS-C sized sensors.

Di II (Tamron) - Tamron lenses which are only suitable for use with digital SLR cameras with an APS-C sized sensor.

DX (Nikon) - Nikon's range of lenses that are only suitable for use with digital SLR cameras with an APS-C sized sensor.

EX (Sigma) - Sigma EX lenses have superior build and optical quality than a non EX lens.

FAJ (Pentax) - FAJ means that the lens has auto focus but no aperture ring, therefore will not be suitable for older manual Pentax SLR cameras.

G (Nikon) - Nikon G series lenses are designed without a manual aperture ring therefore are not suitable for older manual Nikon SLR cameras.

HSM (Sigma) - Stands for Hyper Sonic Motor. Any HSM lens uses a autofocus motor driven by ultrasonic waves to give ultra quiet and quiet AF operation. A Sigma HSM lens will also be fully compatible with cameras without a built in AF motor such as the Nikon D40x and D60 and will give autofocus when used on them.

IF (Sigma) - A lens with IF (Inner Focus) doesnt change its physical length when focusing and the front element doesnt move therefore is ideal when using creative filters as you dont keep having to adjust the filter everytime you focus on your subject.

OS (Sigma) - Stands for Optical Stabiliser and any lens with OS features a built in mechanism that compensates for camera shake which allows you to get good hand held results in lower light conditions.

RF (Sigma) - RF means that the lens has Rear Focus and will be equipped with a system that moves the rear lens group for ultra quick and quiet autofocus operation.

SMC (Pentax) - This stands for Super Multi Coating which is the type of coating on the optics which helps reduce ghosting and flare.

USM (Canon) - This stands for Ultra Sonic Motor and any lens with USM has a built in focus motor and will autofocus quicker and quieter than a non USM Canon lens.