If you want to shoot ultra-close-up images, you need a macro lens. The ‘macro’ badge often seems to be bandied about willy-nilly. You’ll see it applied to zoom lenses that give as little as a 0.33x maximum magnification ratio, or thereabouts, and to prime lenses that only give 0.5x magnification. By comparison, all of the lenses we’ve selected here go the distance, at least when it comes to short focusing distances, enabling full 1.0x magnification at their closest focus setting. But what does that actually mean?
A macro lens with a 1.0x or 1:1 magnification ratio can reproduce objects at full life size on the camera’s image sensor. For example, if you’re shooting with a APS-C format DSLR body like a Canon EOS 750D or Nikon D5600, a postage stamp will fill the whole of the image frame. When viewing photos on screen or in print, this therefore gives the possibility of massive enlargements of the tiny things in life. Shoot a spider or garden bug, for example, and it can take on the appearance of a giant alien invader, complete with astonishing fine detail that’s invisible to the naked eye.
While all of the lenses on test give the same maximum magnification, there’s a wide variation of focal lengths on offer, ranging from 40mm to 105mm. The main difference in practical terms is that lenses with shorter focal lengths have closer minimum focus distances, at which full 1.0x magnification becomes available. A focal length of between 90mm to 105mm is often preferred, as it gives a convenient working distance to the subject, of around 15cm. The minimum focus distance remains the same whether you use a lens on an full-frame or APS-C format camera. However, the 1.6x/1.5x crop factor of a APS-C DSLR gives the appearance of even greater magnification.
Shorter focal lengths can shrink the closest available focus distance. Bearing in mind that the distance is measured from the ‘focal plane’ near the rear of the camera body, rather than from the front of the lens, you can find that the forward end of the lens comes frustratingly close to the subject in macro shooting. Not only do you risk scaring away small bugs that you’re trying to photograph, you can also find that you’re blocking light from reaching the subject. The problem can be compounded in lenses that lack an internal focusing mechanism, because their physical length often stretches considerably as the focus distance is reduced.
Unlike regular lenses, the performance of macro lenses in terms of sharpness and contrast at narrow apertures is an important factor. This is because depth of field can be as little as a millimetre or two at the shortest focus distance, so you often need to use a narrow aperture to enable sharpness at more than one specific point on a three-dimensional subject.
Remember, macro lenses can focus at normal distances too, so they can be used as regular 'prime' lenses and make great portrait lenses.