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
Third-party macro lenses – Introduction
Focal lengths that sit in the 90-105mm range have always been the most popular for macro photography, and there have been some classic lenses that fall into this bracket. Many contemporary versions are based on the older designs, so there are a number of models from which to choose. Virtually every camera manufacturer offers a macro lens in the 90-105mm range, but for this review we will be comparing three third-party models: the Sigma 105mm f/2.8 EX DG OS HSM Macro; the Tamron SP 90mm f/2.8 Di Macro 1:1 VC USD; and the Tokina 100mm f/2.8 AT-X M100 AF Pro D Macro. Each is very highly regarded, with the Sigma lens recently winning AP’s coveted Fixed Focal Length Lens of the Year award for 2013. The Tokina 100mm lens is also very well respected, while the newest lens in the group, the Tamron 90mm, is the latest incarnation of a favourite lens that is around 30 years old.
With such an excellent range of lenses available, it can be tricky deciding which one is right for you. Although sharpness and detail resolution are, of course, critical, there are other factors to consider, such as how easy it is to manually focus the lens, how loud the AF motor is, and what the minimum working distance is. All these elements will have a bearing on how appropriate the lens is for macro photography. Of course, lenses of this length can also be put to other uses – portrait photography, for instance, and particularly head-and-shoulders shots.
Countless 90-105mm macro lenses have been produced over the years, and there is clearly a large market for them, but why are they so popular? In fact, there are a number of reasons why people like these lenses, and not all of them are related to macro photography.
First, the slight telephoto focal length allows the photographer to maintain a suitable working distance from their subject and still achieve a 1:1 magnification. In macro photography, it is vital to allow some space between the end of the lens and the subject, mainly because of the subject itself. Insects, for example, are likely to fly, or scuttle off, should the photographer get too close. The photographer must also avoid casting shadows over the subject – either their own or those of the camera and lens. When working up close to the subject, particularly in natural light, it can be difficult to illuminate the subject well, and it is all too easy to cast an obvious shadow across the scene.
All the lenses in this test have a minimum focus distance of around 30cm, which is significantly greater than the 18cm found on a 50mm macro lens. However, it is important to remember that the minimum focus distance is measured from the nearest point of focus to the focal plane, which is the surface of the film or sensor. Therefore, the flange depth and length of the lens must be deducted from the minimum focus distance to give a minimum working distance, which is the distance from the end of the lens to the subject. The longer the working distance, the easier it is for photographers to light the subject unobstructed and make sure the lens shadow doesn’t fall across the scene.
At around 100mm in focal length, a fixed lens should also show very little, if any, curvilinear distortion. Physically, a lens of this focal length should also be a good compromise between size and focal length. Longer focal lengths will need to be larger and heavier to include an f/2.8 aperture and, as a result, will be extremely difficult to use handheld for macro images.
For portrait images the focal length allows enough distance between the photographer and the subject to maintain a comfortable working space, both for lights and to make sure the subject doesn’t feel crowded. For documentary shots it also allows a photographer to work without the danger of inserting themselves into the scene.
Finally, at around £350-£500, the cost of the lens is quite reasonable. So, in short, excellent image quality is within the reach of most photographers in a lens that is surprisingly versatile, and which makes possible a number of other applications besides macro work. Therein lies their popularity.