Photography News Issue 44

Photography News | Issue 44 | absolutephoto.com

Technique 21

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What to look for in a macro lens

certain degree. This doesn’t affect the focusing distance though, and can make it easier to fill the frame at the maximummagnification. Depth-of-field The closer the subject is focused upon, and the greater the magnification, the shallower the depth-of-field becomes. For this reason, even using a small aperture will produce a shallow depth-of- field with macro lenses when used very close to a subject. You may have only a few millimetres of sharpness to play with, so while the widest apertures are often seen as attractive, they’re less useful when shooting macro. Therefore it’s well worth checking how well a lens performs at smaller apertures (those prone to more softening through diffraction), as this is where you’ll be doing a lot of shooting. Of course, the problem is lessened as you focus further from the lens. Effective aperture A feature common to allmacro lenses is a change to the effective aperture of the lens as you focus closer to the subject. To focus closely, the lens elements and aperture mechanism move towards the subject, and this means the aperture effectively becomes smaller. Some cameras showthis in the shooting settings and somedonot, but the effect is the same; you lose light, so longer exposures or and also limit focusing range; for example, to just the closest settings. 3 Frontelement On some lenses, as you focus closer, the front element racks out, towards the subject, so it’s better to use lenseswhich focus internally. 1 Lenshood The lens hood cuts out flare, caused by bright light sources, and protects the glass fromknocks. Focus really, really close and the hood can get in theway, stopping light reaching the subject. Controls Here you can switch on image stabilisation, set auto ormanual focus 2

4 Filter thread

6 Maximumaperture This states how wide the

8 Reproduction ratio Stated on the barrel next to the focusing distance – you usually get true macro 1:1 reproduction ratio at the minimum focusing distance. 9 Focal length With macro lenses, this is a good indication of how close you’ll be able to frame up on the subject without disturbing it, and howmuch the perspective will be compressed. Typical focal lengths are 50mm, 70mm, 90mm, 105mm, 150mm and 180mm. Tripod collar Like large telephoto lenses, longer macro options will have a tripod collar. 10

This allows you to mount the lens on a tripod via that point, rather than the base of the camera, giving a much better balance and more stability. The collar can also be rotated, so switching from a horizontal to vertical composition is easy. and camera. Of course, it needs to be one that fits your camera make, and a metal lens mount will offer you much greater strength and durability. Some lenses have weather sealing here, too, which will protect the camera and the lens from dust and water getting into the mechanism. 11 Lens mount The mounting point between lens

higher ISO settings are required. The viewfinder may also appear darker which can make checking critical focus a slower process. Buying a macro lens with a fast maximum aperture is still important though, as the lens uses the widest aperture when autofocusing. Relate this to the diminishing effective aperture and slower lenses may lose AF their closest focus distances. If you get an f/2.8 lens it should only close to f/5.6 at closest focus which will still allow AF on the vast majority of cameras. Size, weight and stabilisation Macro lenses with longer focal lengths will likely be larger and heavier than shorter options, but if the lens is mounted securely on a tripod and suitable head, size and weight shouldn’t be a problem. A tripod collar makes this easier. Obviously if you’re handholding the lens, weight is more of a concern, especially as you may find it more difficult to hold steady. Thankfully, that’s where image stabilisation comes in; most macro lenses now use some form of stabilisation for sharper results when handholding, so make sure yours has it. Sigma’s macro lenses feature its proprietary OS or Optical Stabilizer technology to give up to a 4EV benefit when handholding. For nature, this is useful because using a support is not always feasible. Each lens has a filter size, identified on the barrel. Using this thread you can add filters, like polarisers or close up lenses for even more magnification. 5 Focus ring The focus ring is used to manually focus the lens, and in the certain AF modes, you have full-time override to make minor corrections after focus has kicked in. On a macro lens, where manual focusing is critical, you’re looking for lots of grip, a smooth turn and a slow change in the focus setting so that you can achieve greater accuracy.

aperture will open; as almost all true macro lenses are primes there will only be one value stated, but you will also notice that the maximum and minimum apertures vary as the focusing distance is changed – if you focus closer then the values will get smaller etc. 7 Focus distancewindow This shows where the lens is focused between infinity and the lens’s closest focusing distance, measured in metres and feet. Some lenses also have a depth-of-field scale, so you can quickly tell what’s in focus andwhat isn’t.

Above Macro lenses with longer focal lengths are useful when you need to keepmore distance from the subject. This might be to avoid alarming them, as with tiny wildlife subjects, or to avoid casting a shadow from the lens.

Filters and hoods Take note of the lens’s filter size: while you’re unlikely to need neutral density filters in macro photography (the problem is more likely to be getting enough light into the camera to use smaller apertures,

than the opposite), polarising filters can be very useful; they’ll allow you to lower contrast, and reduce glare off foliage, say shiny green leaves, for more saturated results and to reveal surface detail. It’s also useful if a macro lens comes with an APS-C

lens hood adapter. This increases the length of the hood to match the cropped view and is therefore more effective at reducing flare, being longer than the regular hood. You will sacrifice working distance this way, however.