Macro photography is the art of capturing the fine detail of very small subjects that may not be seen by the naked eye. Technically, to fall under the category of “macro,” the subject should be captured with a reproduction ratio of 1:1 (i.e., the subject will be captured on the sensor at 100% life-size).
Macro lenses are specially designed to minimize the focusing distance, allowing the photographer to get closer to the subject and therefore increase the reproduction ratio.
There are a number of techniques that can be used to help achieve the desired magnification without a dedicated lens (extension tubes, close-up filters, and reversing rings). However, one of the less common techniques is to use something that you probably already have in your bag: a telephoto lens.
Telephoto lenses offer extreme magnification, but generally have much larger minimum focusing distances. This pushes the photographer farther from the subject and therefore reduces the reproduction ratio. Some telephoto lenses, when combined with camera systems utilizing smaller sensors, are able to offer 1:1 magnification (true macro). However, typically, telephoto lenses are limited to close-up photography at near-macro reproduction ratios.
Using a telephoto lens for this kind of work offers a couple of advantages over a dedicated macro lens that are a direct result of the large minimum focus distance. Because the working distance to the subject is in the region of 1 meter (compared to the 15-30 cm working distance of standard macro lenses), the risk of disturbing your subject as you compose your shot is much reduced.
Also, given the extra distance between the camera and the subject, you are much less likely to cast a shadow over your subject. And you have a lot of freedom with the lighting you can employ to light the subject, both natural and flash.
Using a telephoto lens for such precise work is not without challenge, so here are a few tips to help maximize your chances of getting that near-macro shot with your telephoto lens:
- Due to the extreme focal length, the risk of reduced sharpness due to camera shake is higher. Therefore, it is imperative you use a tripod and a remote shutter release to try to limit camera movement.
- Even on a tripod, images can suffer from camera shake. Try to use a tripod collar for your telephoto lens. That way, the lens is clamped directly to the tripod, reducing the chances of lens wobble. If not, use the “1/focal length’” shutter speed rule to help capture sharp images. (I always use 1/effective focal length, where you multiply your focal length by the sensor crop factor to give the focal length in 35 mm terms.)
- Be aware of the depth of field. Using extreme focal lengths at such close distances can reduce the depth of field to fractions of a millimeter. Therefore, to ensure the subject is sharp throughout, use a small-enough aperture to ensure the depth of field extends across your whole subject (there are websites and apps to help you do this).
- If you want to capture your subject in focus from front to back, ensure that it is parallel to your sensor. The depth of field will be so narrow at the extreme focal lengths that you may not have more than a few millimeters of depth of field to play with. Therefore, position yourself accordingly to maximize your chances of capturing a sharp image.
- If your telephoto lens has an AF/MF switch, switch it to manual focus and compose/focus the shot manually. You may find that, when focusing manually, the minimum focusing distance decreases. This means that you can get closer to your subject, increasing the magnification.
- Use a teleconverter to increase the focal length while retaining the same minimum focusing distance. This will allow you to significantly increase the magnification of the subject without having to move any further away. Increasing the focal length in this way will have consequences on your choice of shutter speed and aperture, but as long as you take this into consideration, a teleconverter can successfully be used to increase the reproduction ratio.
Using a telephoto lens for near-macro photography will typically not allow you to magnify your subject as far as if you were using a dedicated macro lens. But you will be able to test the water to see if macro photography is something you enjoy without having to spend on any additional kit.
If you do decide that macro photography is for you, by putting this technique into practice you will learn a lot of good fieldcraft that will be beneficial when you get around to picking up a dedicated macro lens.