Super Macro Underwater Photography - The Definitive Guide, Part 2A
Part 2A – An Intro To Super Macro Tools
by Keri Wilk
Now that you have an understanding of general macro and super macro terms, lets explore some of the tools we use for underwater super macro photography. In this installment we will discuss macro lenses and teleconverters. Part 2b will cover extension tubes and diopters.
Generally, to shoot in the super macro range, you’ll need to use a “standard” macro lens (i.e. a lens that allows up to at least 1:2 magnification) in conjunction with one or more specialized supermacro tools, which will be discussed below. There are dozens of these macro lenses available for DSLR systems, from a variety of manufacturers, but the Nikon 105mm/60mm and Canon 100mm/60mm lenses are probably the most popular amongst underwater photographers. Here is a list of some other popular 1:1 macro lenses available:
This characteristic might not seem terribly significant to you at first glance, since all of the lenses mentioned above can achieve the same level of magnification, but your choice of super macro tool can be directly influenced by the working distance of your primary macro lens.
The term “minimum focus distance” should not be confused with “working distance”. A lens’ minimum focus distance is actually the smallest allowable distance from the film/sensor plane to the subject – NOT the lens to subject distance. Notice how different the minimum focus distance and working distances are for any given lens in the chart above. Often the working distance is less than HALF of the minimum focus distance. To avoid disappointment, keep this in mind when you’re researching the next macro addition to your lens family.
Intro To Super Macro Tools
A smorgasbord of tools have been designed to achieve high levels of magnification, with each type of tool having its own set of pros and cons. The choice of a super macro tool should be based on the consideration of several factors that may be relevant/important to you, possibly including:
- magnification level
- tool versatility (interchangeable vs permanent)
- practicality (working distance? ease of use?)
- water clarity (clear vs murky)
- intended subjects (static vs shy)
- intended image use (web vs large prints)
These optical tools are inserted between your primary lens and camera body. Also refered to as TC's, tele-extenders or negative suplementary lenses, teleconverters are designed to change the effective focal length of your primary lens by a specific multiplication factor (typical values being 1.4X, 1.7X, 2.0X or 3.0X) without affecting working distance. I say effective focal length, because the actual focal length of the primary lens remains unchanged, while the resulting (larger) image will look like that produced by a longer focal length lens shot at the same distance. It is important to note that the increase in effective focal length is accompanied by a decrease in effective aperture, i.e. the effective F-stop increases by the same multiplicative factor. For example, a 100mm F2.8 lens with a 2X TC becomes an effective 200mm F5.6 lens.
The effects of teleconverters are illustrated in the following diagrams.
Another drawback is that once you set up your underwater camera rig with a particular TC/lens combination, you’re committed to it for the entire dive. So, you might end up kicking yourself when you stumble across a mating pair of frogfish just outside your subject-size range. Before committing to the use of a teleconverter, consider doing some research or even a preliminary dive or snorkel to scout out subjects at a dive site.
Lastly, since teleconverters contain several optical elements, they inherently degrade image quality to some degree. In addition, TC's actually amplify any optical problems
If you need to maintain maximum working distance and don’t mind devoting a dive to a particular subject size/magnification level, then teleconverters might be the right tool for the job. Just remember the possible image degradation when stacking them, and make sure your strobe batteries are charged, because in many cases you’ll need all the power you can get!
Richard A. Morton, “Photography for the Scientist”, 1984
Charles E. Engel, “Photography for the Scientist”, 1968
Rudolf Kingslake, “Lenses in Photography”, 1951
Rudolf Kingslake, “A History of the Photographic Lens”, 1989
Leonard Gaunt, “The Photoguide to the 35mm Single Lens Reflex”, 1973
Francis A. Jenkins and Harvey E. White, “Fundamentals of Optics”, 1957
Leslie Wilk, www.scubageek.com, 2009