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Photo Tips
Choosing a Macro Lens
By Adam Jones
A lot has been written about macro lenses and which focal length is best. Most manufacturers offer macros with focal lengths falling into three categories, 50mm, 90-100mm, 180-200mm. All three focal lengths can get you close-up while delivering extraordinary image quality. So what is there to debate? Several factors are worth considering when making this important purchase. Price is certainly important, hopefully not the main deciding factor. For example, a Canon 50mm F 2.5 costs roughly $250.00, a 100mm F 2.8 is about $500.00 and a 180mm F 3.5 is $ 1,200.00.
© Adam Jones
Price roughly doubles each time the focal length is doubled. Two very real reasons keep me from considering a normal focal length (50mm). First, is the extemely close working distance required to magnify small subjects, and second is the lack of background control. Simply put, I would not consider a 50mm macro as my workhorse lens for fieldwork. If you are on a tight budget and you only do occasional macro work, a normal focal length macro may suffice.
© Adam Jones
Most modern macros focus to 1:1 magnification without additional accessories. This simply means a lens fills the frame at its closest focus with a subject the size of one frame of 35mm film. Focal length is worth considering for two important reasons. The first is working distance; which is the distance from the end of the lens to the subject. Telephoto macros produce the same size image as a normal focal length macros, but they do it further from the subject and that is a great advantage in the field. For example, to fill the frame with the image of a 35mm-film cassette, a 50mm macro lens is only two inches from the film cassette. For the same image size, a 180mm macro is 12 inches from the subject.
© Adam Jones
In the field, the extra working distance is a tremendous advantage. For fieldwork, consider at least a 90-100mm lens. Active subjects seldom allow an approach within two inches, but many creatures will tolerate your lens at 12 inches. Another advantage of longer focal lengths is realized when lighting tiny subjects with flash or reflectors. Lenses placed only an inch or two from the subject allow practically no room for positioning reflectors or flash units for supplemental lighting. Ask yourself one question. Do I really want to struggle positioning a tripod-mounted camera within a few inches of every small subject?
© Adam Jones
Selective background control is the other huge advantage realized with longer focal lengths. The narrower telephoto angle of view simply sees less behind the subject. With telephoto designs, small adjustments in camera position result in big changes to the background. Often the only way to eliminate a messy background is to back up, and shoot with a longer lens. Of the three focal lengths discussed, only the longest is supplied with a tripod collar. The added stability, balance, and convenience is worth the extra cost. Bottom line, they all work, but the advantages in working distance and background control make the longer focal lengths more useful. Close-up photography in the field demands exacting skills, longer lenses simply make working in the field a lot less aggrevating and a whole lot more fun. Over the years, I’ve owned all three focal length macros as a working pro, and today, I almost exclusively use a Canon 180mm macro.
© Adam Jones