Richard Sibley compares APu2019s Fixed Focal Length Lens of the Year, the Sigma 105mm f/2.8 EX DG OS HSM Macro, with 90mm and 100mm optics from Tamron and Tokina, and explains why such focal lengths are so enduringly popular
The Tamron lens has the largest focusing ring. The ring has a good grip and smooth operation, and doesn’t feel as though it will slip out of focus. The Tokina 100mm lens has a grip about the same width as that of the Sigma 105mm optic, but with a smoother feel and is less stiff than the Sigma when focusing. Having used all three lenses to manually focus, none was especially difficult to use. While the focusing ring of the Sigma lens might require a firmer turn, it also doesn’t feel like it will ever slip out of focus once set.
Both the Tamron and Sigma lenses have switches on the barrel to change between manual and autofocus, but the Tokina uses a push-pull clutch mechanism to switch between the two modes. It is a system Tokina has used for a number of years, and although it works well, it does feel a little dated. Many lenses now have AF/M modes that allow the AF to be overridden simply by turning the manual-focus ring.
Each of the lenses has a focus limiter. Restricting the focus range according to the type of subject being photographed makes the AF faster for macro as well as for general photography. The Tamron 90mm and Sigma 105mm lenses have two different focus-limiter settings, in addition to the full focus range: one designed for close-up use, and another for distance. The Tamron optic can be set to 50cm-infinity or 30-50cm, while the Sigma lens has the option of 31.2-45cm or 45cm-infinity. The Tokina lens has only a simple switch reading Full or Limit, with the limited range being 128cm-infinity. This is great for general use and portraits. Given that this is a macro lens, though, it is a shame that there isn’t the option to limit the focusing to closer distances.
Unlike its predecessor, the new Sigma 105mm lens features internal focusing. This means that the lens will always remain the same length, with all the elements moving inside the barrel. This is also the case with the Tamron 90mm lens. This feature is useful when shooting macro images as it gives the user complete awareness of their working focus distance, and lessens the risk of bumping the front of the lens against the subject or its surroundings.
In contrast to the Sigma and Tamron lenses, the Tokina optic does not focus internally, so a helicoid lens-barrel system causes the length of the lens to extend as the focusing ring is turned. This is obviously something to note when photographing subjects close up. For example, when photographing insects, be careful not to nudge a leaf that an insect may be sitting on as the lens extends during focusing. The Tokina optic has an advantage in that its front element sits quite far back from the front of the lens barrel, which in effect acts as a kind of built-in hood, shielding the lens from stray light that may enter at acute angles. However, this also means that the front element can’t get as close to the subject. A lens hood is also included, as it is with each of the other lenses.
Images: In the pull-up of the flower taken with each lens, it appears that the Tamron and Sigma optics are equally sharp and have the edge over the Tokina lens