Close-up: Stacking, Reversing and Other Lens Gymnastics
In addition to the various ways of getting into the realm of macro by adding extension that we went over last week, there are a number of other options. In contrast with extension tubes and bellows, all of these involve the use of additional glass elements or other ways to significantly modify the image produced by the lens.
I've written extensively on close-up diopters before so I won't add too much here. For most people, diopters represent the easiest and certainly cheapest way to get into the world of macro.
- Compact — fits easily in camera bag
- Works with the lenses you already have
- Not quite as good as a true macro lens
Stacking a Lens
Instead of a close-up diopter, what if you simply stacked one regular lens in front of another? Well, it turns out this isn't as wacky as it might sound. You can buy a simple coupling ring with male threads on both sides that will allow you to do just this. Simply screw one side of the coupling ring into the filter threads on the front of your main lens, then reverse a second lens with the same filter diameter and screw its filter threads onto the other side of the coupling ring.
Not every combination works well of course. First, as mentioned, the stacked lens needs to optimally have the same diameter filter threads as your main lens. Step up and step down rings can bridge any gap, but you are inviting vignetting and other image quality problems if the diameters differ. Second, the focal length of your main lens needs to be significantly longer than that of your stacked lens in order to achieve any meaningful increase in magnification. We'll cover some formulas in future weeks. And thirdly, while your main lens can be a zoom, the stacked lens should not be.
When you stack lenses, you have two apertures to contend with, and two focus rings. Dealing with this multiplicity of choices isn't really that much of a problem though. Set the aperture of your stacked lens wide open and control your exposure with your main lens. Because your range of focus distance will be so limited, the actual focus setting on the stacked lens doesn't matter too much, but it is commonly set at infinity focus.
My two favorite stacked combinations with Nikon lenses both involve the use of the 200mm manual focus micro lens as my prime lens, with either the 50mm f/1.8 AF or the 28mm f/2.8 AF stacked on top. Magnification with the former is about 4x life size while the 28mm gives nearly 6x life size. Wow.
- Easy way to get to high magnification
- May work with lenses you already have
- Possible vignetting
- Not all combinations work well
The optical formulas of regular lenses are optimized for reproduction ratios less than life size. Reversing a regular or shorter lens on top of a longer lens in theory optimizes it for greater magnification simply by reversing the path of light through its elements. But what if you want to reverse the lens by itself directly on your camera body? This generally doesn't give you much of an increase in magnification but is possible. For Nikon shooters, the BR2A adapter provides 52mm male filter threads on one side that will attach to the threads on the front of a lens (the Nikon BR5 is a sort of inside-out 52mm to 62mm step-up ring, useful if your lens has 62mm threads instead), and a regular bayonet mount on the other side to mount on your camera. Fun to play with, but there are better ways to get to macro. Keep in mind that all electrical and mechanical coupling between the camera and lens has been severed so you are on your own for metering. You'll need a lens with an aperture ring too since it is up to you to stop it down to your selected shooting aperture.
- Optimizes lens for greater than life size
- No meter coupling
- No aperture coupling
Unlike a diopter or stacked lens, a teleconverter is an auxiliary lens that goes, not on top of your main lens, but between it and your camera body. Teleconverters are more commonly associated with telephoto and wildlife shooting, but they can also be useful for macro, enabling you to get a shot from further away. Since most lenses won't get anywhere near life size on their own though, magnification with even a 2x teleconverter will still be somewhat limited.
Teleconverters can be used in conjunction with extension tubes to useful effect as we'll see when we discuss mixing and matching next week.
- Useful, but somewhat limited for true macro