All but one of the eight macro lenses on test are in the mid-telephoto, category, which is around 90-105mm, and the only lens that isn't – the Olympus Zuiko Digital ED 50mm 1:2.0 Macro – is designed for bodies on which its effective focal length becomes 100mm.
The pricing of these lenses is consistent with their focal length, being higher than shorter macro optics and lower then longer ones, but the cost still varies. The image stabilisation systems in both the Sigma 105mm f/2.8 EX DG OS HSM and the Nikon AF-S VR 105mm f/2.8G IF-ED partly explains why these are the second and third most expensive options here. Other variables include autofocus technology and whether the lens is capable of focusing internally.
The latter point is important for macro shooting because it means that a lens can focus without its inner barrel extending outwards. This prevents the lens inadvertently touching the subject, and reduces the likelihood of shadows from the lens being cast over the subject.
It's also worth bearing in mind that a longer lens will typically have a longer minimum focusing distance than a shorter lens.
The shallow depth of field obtainable with longer lenses also means that it's easier to separate your subject from its background, although considering just how shallow this can be, shooting at the wider apertures may be unfeasible for much macro work.
It's advisable, therefore, to set a smaller aperture when shooting very close up, to ensure the entire subject is in focus.
The lenses on test focus from very close up to infinity (much of their focusing range isn't used when shooting close up), and it can take a while for a lens to work through this entire range when it seeks to focus on a subject. Fortunately, many macro lenses feature focus limiter switches, which can be used to close off a part of the range that isn't required, allowing focus to be acquired sooner.
Although the lenses on test are designed primarily for macro photography, they can be used successfully for other genres. The eight on test are high-quality medium telephoto lenses, each claiming to be corrected for distortion and chromatic aberration, and designed to record a high level of detail.
On bodies with full-frame sensors their focal lengths are particularly suited to portraiture. On bodies with APS-C or smaller sensors they can be used for many types of nature photography, because their relatively wide maximum apertures help to isolate subjects from their backgrounds and maintain fast shutter speeds.
Their low distortion also means that they can be useful in product photography too, while food photographers are also likely to appreciate their maximum aperture and focal length.