Looking for a keenly-priced macro for autumn
and winter? We find eight of the best buys, starting from under $300
Macro lenses are
close-up specialists, usually offering a full 1x magnification factor at their
closest focus setting. It’s not always the case, though, as demonstrated by the
Canon 50mm macro in this group, which only offers 0.5x magnification. The most
popular focal length for macro lenses is around 100mm, especially on full-frame
cameras. This enables you to keep a not overly threatening distance from bugs
and other timid little creatures when you’re shooting them. So why go shorter?
This
is about as close as you can get with most non-macro optics.
On cameras with APS-C sensors, a 50mm macro
lens has an effective focal length of around 75-80mm. That’s not only edging
towards the 100mm focal length favoured by full-frame photographers, but is
also ideal for portraiture. Indeed, these lenses are often referred to as
‘portrait macro’ lenses for APS-C bodies. As macro prime lenses, they should
not only be super-sharp with negligible distortion, but offer a reasonably fast
maximum aperture of around 172.8. This is effective for blurring messy
backgrounds in portrait shots.
Prime time
The Canon 50mm, Nikon 60mm, Sigma 50mm and
Sony 50mm lenses in this test group not only work on APS-C bodies but are also
fully compatible with full-frame cameras. In this case, they double up as
useful ‘standard’ prime lenses, closely matching the perspective of the human
eye for general shooting.
One thing common to all macro lenses is
that they’re designed to be ‘flat field’ lenses. At short focus distances, they
aim to have little or no field curvature, so the centre, edges and corners of
the frame are equally focused at the same object distance. For example,
consider you’re photographing something flat like a postage stamp from head on
(a stamp will practically fill the whole frame with a 1x magnification macro
lens on a body with an APS-C sensor). A flat field design will ensure that the
whole of the stamp is sharp in the image when the lens is focused correctly.
It’s an important consideration because, even at small aperture settings, depth
of field is tiny at 1x magnification.
We’re often concerned with a lens’s
performance at its largest available aperture, where sharpness often drops off.
But for macro lenses, where you often need to use a small aperture to eke out a
little extra depth of field, good sharpness and contrast is also very desirable
at around f/16. This is difficult to achieve due to the effects of diffraction
(bending of light rays), which become more problematic at small apertures.
How much difference does aperture really
make to depth of field in macro shooting? Let’s take the Canon 60mm lens on an
APS-C body as an example. At its closest focus setting of 20cm, an aperture of
f/16 will give you a depth of field of about 4mm in total. Shrink the aperture
to f/5.6 and the entire depth of field is reduced to just 1.7mm.
Mind the gap
Whereas a 100mm macro lens will have a
closest focus distance of about 30cm, it’s only about 20cm for a 50mm macro
lens. However, this isn’t the gap between the front of the lens and the subject
you’re shooting. Instead the focus distance, as always, is measured from the
‘focal plane’ (the position of the image sensor in a digital camera) and the
subject. Since the image sensor is towards the rear of the camera and the lens
itself cuts into the distance, the gap between the front of the lens and what
you’re shooting can end up being very small.
A
true macro lens enables you to fill the frame with small details.
To make matters worse, while some macro
lenses in this group have internal focus mechanisms, others don’t. The front
elements of the Canon 50mm, both Nikon lenses, and the Sigma and Sony lenses
all extend forwards as you focus down towards the closest focus distance. For
example, the Sony 50mm has a stated length of 67mm. However, it extends to
114mm at its closest focus setting.
Add on the depth of the image sensor within
the attached camera body and its front element comes to just 5cm from the
object you’re photographing when using the closest focus distance. You can
often find that the lens casts a shadow over what you’re shooting, or at least
cuts out some of the light on the subject. Illumination from a camera’s pop-up
flash can also be obscured and, if you need to light the subject from an
oblique angle, it’s easy to end up with deep but unwanted shadows (see
Ringflash Explained).
Getting back to the use of these lenses in
general photography, bear in mind that macro lenses often have a very long
focus travel. This helps to enable precise focusing in critical macro work.
However, it can make autofocus very slow, so a focus limiter switch can be
useful, as described in Features to Look For.
Kit anatomy - Close-up options
Buying a macro lens isn't the only in-road
to close-up photography. The cheapest alternative is to buy close-up filters,
made by the likes of Hoya and Kood. These screw into the filter thread of a
lens, their dioptre enabling closer focusing and greater magnification. They're
available in different strengths and can be stacked for greater effect,
although you can expect a progressive loss in image quality.
Another option is to fit extension tubes,
which mount between the camera body and the attached lens. These don't contain
any glass elements, but simply move the lens further away from the camera.
Again, they're available in different strengths, but cheaper versions don't
feature any electronic connections between the attached lens and camera body,
so autofocus and exposure metering are impossible.
Yet another alternative is a reversing
ring. In this case, one lens is mounted to the camera, but a second lens is
reversed and attached to the primary lens via the reversing ring. It's an -
unwieldy set-up, but can yield good results.
How we test lenses - Advice you can trust
Our testing procedure includes lab tests
under controlled conditions, as well as 'real-world' shooting. Firstly, all
lenses are fitted to mid-range cameras and used to take images of two test
charts under studio lights. The results are processed using Imatest Master, so
that we can quantify optical performance in terms of sharpness, chromatic
aberrations and distortion. Overall quality is assessed at the centre, edge and
corners of the images.
For real-world conditions, we use each of
the lenses under widely varying indoor and outdoor lighting conditions. Overall
handling is checked, as well as the smoothness and precision of zoom and focus
rings, and the operation of all switches. We also test the speed and accuracy
of autofocus systems, complete with operation of full-time manual override
where available. Ratings are finally given for features, build . quality, image
quality and value for money.
