Photo Tip: Macro Photography
Tools
What is Macro Photography?
"Macro photography" is simply another name for "close-up photography." The closer you can focus on your subject the larger it will appear in the frame, which is the point to macro photography -- to magnify small objects. Some purists insist that the term macro be reserved for images that are at least life-sized in the film -- an object 1" long must record an image 1" long or longer in the film to count as macro to these folks.
I prefer to speak more loosely of macro photography as being anything that uses some sort of technique that yields an image more magnified than would be possible with just an ordinary lens on the camera. For me, macro photography can have relatively small magnification factors -- just as long as there is more magnification than with a conventional lens by itself.
By the way, some people use the term "micro photography" instead of macro photography, but it's the same thing.
What is it good for?
Macro photography lets you fill the frame with small subjects. A picture of a caterpillar taken with a 50 mm lens from 10 feet away is likely to be uninteresting because the subject is a tiny speck in the photo. Make that same caterpillar fill the frame of film, however, and you've got an exciting photograph.
But you can do more than simply enlarge small subjects to fill the frame. You can use enough magnification to overfill the frame with the subject, abstracting out one part of the subject to stand for the whole. With enough magnification, you can make the photo an interesting abstraction where the viewer can't even tell what the original subject was. The possibilities of macro photography are limited only by your imagination.
I show some examples of macro photography in another photo tip.
Macro Methods
There are several techniques one can use to make macro photographs. You are can also mix and match these techniques, using more than one at a time to get just the right amount of magnification, or to achieve a tremendous degree of magnification.
The photo below depicts the tools I'll discuss.
extension tubes
When you focus a lens you turn a ring on the lens barrel that is geared to move the lens in and out of the camera, toward and away from the film. The further away the lens is from the film, the closer the focus. But lenses have only so much travel built in to them, so there is a limit to how close you can focus. By adding extra space between the lens and the camera body, you move the lens away from the film and thus focus more closely than you would otherwise have been able to. Closer focus, more magnification.
The thing you put between the lens and the camera body is simply a spacer called an extension tube. The extension tube is totally hollow, it has no optical elements. Extension tubes come in a variety of sizes -- the more extension, the greater the magnification. One handy formula to remember is that if the extension is equal to the lens focal length, then you will get life-size magnification on the film: this is true macro, even to purists.
If all you have is a short extension tube, this formula tells you that you'll get more magnification when using shorter focal length lenses. But it may well be worth investing in a longer extension tube and using longer focal length lenses. The longer lens not only gives you a narrower field of view, making background distractions easier to shoot around, but it also gives you a larger working distance between lens and subject.
When using an extension tube, be sure to use one that maintains all the couplings between your lens and your body. I always use Nikon extension tubes with my Nikon equipment just to make certain the lens will work as if the extension tube weren't there at all. The lens just acts as if it had extra travel built into it.
Extension tubes are my favorite tool for macro photography. This is because they don't introduce any optical elements into the light path. The more lenses involved in making a photograph, the less sharp the end result will be, and by adding nothing to the light path, extension tubes leave my images as sharp as my lens is capable of.
On the other hand, the extension moves the lens aperture farther away from the film, and so by the inverse-square law of light falloff, the image on the film is fainter. This leads to longer exposure times, which is sometimes a pain. If I'm shooting a flower and there are puffs of wind, I may lose the shot if I try using an extension tube. For example, when shooting life-size macro using lens extension, you lose two full stops of light. If you have TTL metering, your camera meter sees this dimmer light and automatically gives you the correct exposure to use. But if you are using a separate light meter, you have to figure out how much exposure to add by means of a calculation.
Another disadvantage of using extension tubes is that you lose the ability to focus at infinity. You make the lens able to focus more closely by taking away its ability to focus far away.
macro lenses
Some lenses have extra travel built into them. In essence, they have extension tubes incorporated into their design. These lenses are called macro lenses. They are things of beauty. Not only can they focus close because of the built-in extension, they retain their ability to focus out to infinity. They are also designed to be extra sharp, and will probably be the sharpest lens in your bag, even when used conventionally for non-macro shots. Their only disadvantage is their high price.
Beware! Some lenses labeled "macro" are anything but. Since a lens gives its highest magnification at its closest focus, some manufacturers label this closest focus point as a "macro" setting and try to foist it off at a high price on unsuspecting customers. A true macro lens is a gem, but these false macro lenses are pure advertising hype.
close-up filters
There are attachments that contain magnifying lenses that screw on to the threaded front of your lens. These go by various names: close-up attachments, diopters, close-up filters. They are essentially reading glasses for your lens. They have the advantage that there is no light loss, as there is for lens extension; they have the drawback that, being an extra optical element in the light path, they will degrade the image quality to some extent.
There are two types of these close-up attachments out there: those using simple lenses and those using doublet lenses. The simple lenses are cheap, but have horrible optical quality, especially at the edges of the frame. The doublets are more highly optically corrected and will give much better images, albeit at a higher price. In my opinion, the cost is worth it -- avoid the cheapies, get the good ones. The only manufacturer of the good doublets I know of is Nikon. Nikon makes them in two strengths and two filter thread sizes, for a total of four on the market. Nikon's designation for them is 3T and 4T (52 mm threads) and 5T and 6T (62 mm threads), and they cost about $75 or so each. Since they just screw into threads on your lens, you can use the Nikon attachments on any lens (with the right thread size) -- you don't need Nikon equipment to use them.
teleconverters
A teleconverter, like an extension tube, goes between your lens and your camera body. Unlike extension tubes, teleconverters (also known as tele-extenders) have lenses in them. These lenses act to increase the focal length of the lens in use. Increased focal length means a smaller angle of view, which in turn means objects appear larger in the frame. Voila! -- macro. Now, increased focal length wouldn't help if you had to stand farther away to use it. The beauty of teleconverters is that, while changing the focal length of the lens, they don't affect the distance of closest focus. In this case, if you double the focal length of a lens, you double its magnification.
reversing a lens
A lens is designed to take light in its front end and bend it sharply into a stubby cone converging to the film plane. If the lens is turned around, light is perfectly happy to take the same path in reverse -- sharply diverging light from an object very close to the lens' rear element will be focused on the film. This lets one achieve very high magnifications, especially with wide-angle lenses.
The only device you need to invoke this technique is a "reversing ring," a metal ring that has the camera mount for your brand of camera on one face. The other face is threaded so that you can screw on the lens using its filter threads. The reversing ring thus firmly attaches the lens to the camera so that the front of the lens is reversed and facing the film.
When the lens is reversed you've lost the couplings between the camera body and the lens. This means you can't set the aperture ring to a small aperture yet still see the scene through the widest aperture -- unlike conventional photography, the aperture actually closes down as you turn the aperture ring to larger f-numbers and you'll see the viewfinder image dim. (You also lose the ability to operate the camera in program mode or shutter priority mode, both of which require the camera to operate the aperture for you.) You can still meter, though. It's called "stopped-down metering" because you are metering the light as it comes through whatever stopped-down aperture you've selected. You must work in manual or aperture priority mode, using shutter speed to give you the correct exposure given the aperture you have selected. If the stopped-down image turns out to be too dim for your camera's light meter to operate, meter with the lens wide open and calculate the stopped-down shutter speed yourself. You will want to focus with the lens at its widest aperture (slimmest depth of field) in any event.
stacking lenses
Stacking lenses amounts to using one of your camera lenses, reversed, as a front element to another lens that is mounted normally on your camera. John Shaw likens this to using a super-high quality close-up filter. As with a single reversed lens, the reversed lens here is designed to bend light sharply at its rear element. The drawing below shows why this works. There are "lens coupling rings" you can buy that are threaded on both sides to screw two lenses together face-to-face using their filter threads. In a pinch, you can just tape the lenses together instead.
Leave the outer lens -- the reversed one, farther from the camera -- with its aperture wide open, and use the inner lens normally, taking advantage of the lens-body couplings. Make the focal length of the inner lens longer than that of the outer lens. The magnification you will achieve is the ratio of the inner/outer focal lengths. (In the photo above I used lenses of 200 mm and 50 mm for 4X magnification, but you can use other combinations.) Sometimes you'll get vignetting (darkening at the corners of the frame) because in this long, complicated, light path there may be parts of the lenses getting in the way. You can try to mix and match lenses to find a combination that doesn't vignette. Or you can add some extension between the lens combo and the body. Or you can stop down the outer lens (at the cost of returning to what is effectively stop-down metering).
How well do they work?
To illustrate the types of results you might get, I have enlisted the aid of my friend Buzzie:
Buzzie here is photographed with a 105 mm lens with no macro aids.
This is as close as this lens can get on its own.
Now here are the results using various macro aids:
 105 mm lens + 12 mm extension |
 105 mm lens + 50 mm extension |
 105 mm lens + 3T diopter |
 105 mm lens + 4T diopter |
 reversed 50 mm lens |
 reversed 24 mm lens |
 stacked 50 mm + 105 mm lenses |
 stacked 50 mm + 200 mm lenses |
Note that the examples using the stacked lenses illustrate the vignetting at the corners I warned you about. Do not fear: this problem can be avoided.
Accessories
You will usually want to use a tripod when doing macro photography. For one thing, with such close views, even the smallest of moves can change the photograph radically and you will want a stable shooting platform. Moreover, the depth of field in macro photography is extremely limited. When shooting at life-size (1:1) magnification, for example, the depth of field is only 1/8" on either side of the subject plane, for 1/4" total, even when stopped down to f/22! Unless you want to give up on this slim zone of sharpness, you'll be doing a lot of macro shooting at f/22. This means slow shutter speeds if you are shooting with available light, hence, additional need for a tripod.
Another very useful accessory is a "focusing rail." The focusing rail has two parts that slide across each other. You attach the camera to one part, the tripod to the other, and you can then move the camera back and forth toward and away from your subject to achieve accurate focus. Usually this is done with a rack and pinion mechanism for precision and ease of use, with a locking mechanism to freeze the camera in place once you have it adjusted the way you want it. Why not just use the usual helicoid focusing mechanism built into the lens? This would move the lens toward and away from the film as you moved it away and toward the subject. It turns out that the magnification of the subject on the film depends on both the distance from lens to film and from lens to subject. By using the helicoid, you are changing both distances at the same time and mucking with the magnification at the same time you are trying to focus. Sometimes improved focus comes at the same time that increasing magnification serves to magnify any residual blur -- the increased magnification essentially cancels out the improved focus, and the visual appearance in the viewfinder is that the focus isn't changing at all! Most confusing. When you use a focusing rail -- leaving the lens-to-film distance constant -- the magnification stays much more constant and it is much easier to compose and focus the picture you want.
Lighting
With macro photography, if you are shooting with available light, the fact that you are shooting a small target means that the light is easy to modify with reflectors and diffusers. You don't have to cover much area with your reflector or diffuser. But as described above, you are likely to be using long exposure times to maximize depth of field. If you are using lens extension, the exposure times will be just that much longer. If you are shooting indoor still-lives, that isn't such a problem, but if you are shooting outdoors then a slight breeze can kill you. If your subject will move in the breeze, you can always try to stabilize it with wire, clothespins, twine, or whatever is at hand, just so long as this won't harm the subject.
Alternatively, you can use flash to freeze the motion of the subject. This is especially handy if it's alive and may crawl or fly away from you! Generally speaking, soft, relatively shadowless light is pleasing in macro photography, so a single flash with its harsh, directional light isn't a good solution. Special ring flashes are made which surround the lens with a circular flash tube, so the subject gets light from all directions at once. Often photographers will use two flashes mounted on either side of the camera on a bracket so the light comes at the subject from both sides for uniform illumination. One feature of a flash-illuminated macro shot is that the background, being far away compared to the distance of the subject, is unilluminated by the flashes and records on the film as a strong black. When done well this results in the subject standing out, isolated from distracting visual elements. When done poorly, it results in a highly artificial look to the photograph.
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