LENS SPECIFICATIONS WHAT TO LOOK FOR The key things to take into account when deciding which lens is right for you

Prime lenses offer a fixed focal length, while zooms include a range of them. This is expressed in mm, with 50mm representing the ‘standard focal length’ for a full-frame camera. Lenses with smaller focal lengths than this are known as wide-angles, while lenses of 70mm or more are called telephotos. Lenses have different diameters for their filter threads, typically ranging from 58mm to 82mm. You may need to factor in the cost of additional filters or filter adaptor rings when upgrading. The widest aperture offered by a lens is usually expressed alongside its focal length. Many zoom lenses have a ‘floating’ aperture, which means it gets narrower as the lens is zoomed closer. Lens designers use multiple elements to correct optical aberrations. Look for aspherical or low-dispersion elements in lenses: they will have initials such as LD, SLD, ULD or ED in their names. If wildlife is more your thing, then a lens that has an equivalent focal length of 300mm or longer is pretty much essential. A 50mm lens is a good general-purpose lens, perfect for everything from full-length portraits to documentary-style shots.

Avoid duplicating focal lengths in your collection – there’s a reason Canon offers an 11-24mm, 24-70mm and 70-200mm trio in its professional lens range.

Focal length is the distance in millimetres from the optical centre of a lens to the focal point on the camera sensor. It’s a physical property of the lens and doesn’t change. What can change is the ‘angle of view’, which depends on the camera it’s attached to.

The angle of view is essentially what the camera sees through the lens. As the name suggests, a wideangle lens gives extensive coverage.