Photographing plants in their natural settings takes a bit of practice. Plants rarely cooperate by isolating themselves from their surroundings, resulting in photos of subjects that are nearly indistinguishable from their backgrounds. Here are a few suggestions.

Depth of field. Too much depth of field, and you can’t isolate your subject from the other plants that are often behind it. Too little, and you can’t get enough of your subject in focus. If there is a general solution to this problem, I haven’t found it. I try to take several photos of each plant, at different angles and often different apertures, to get one or two that look good. I often shoot at ƒ/11 or ƒ/16, since these smaller apertures increase depth of field. For very small subjects, a point-and-shoot camera is often a better choice than a DSLR, since its smaller sensor has better depth of field.

Here is a concrete example. I usually shoot with a Nikon D300, which has an image sensor that is about two thirds of an inch across. With a 60 mm macro lens, shooting from a distance of two feet, the depth of field is roughly two inches, not enough to bring very much of a typical subject into focus. And that’s at ƒ/16 (smaller apertures have better depth of field). At ƒ/2.8 the DOF is only 1/2 inch. At a distance of six inches, even at ƒ/16, the DOF is even shorter. Check out this depth of field calculator.

One way around this is to take several photos that concentrate on different features. Instead of trying to bring foliage, stem, and flowers into focus in a single shot, take several that emphasize different parts.

This photo of Bishop’s caps was taken with a point-and-shoot camera. Each flower is only about a quarter inch across. The smaller sensor’s deeper depth of field is evident, because the house in the background is about 20 feet distant, and in relatively sharp focus.

Macro lenses. Unless you’re mostly cataloging trees and shrubs, macro lenses are essential. Many point-and-shoot cameras have built-in macro capability, but if you have a DSLR, you’ll need a macro lens. They come in different focal lengths. Shorter lengths, e.g. 60 mm, are lighter and cheaper, but you have to be closer to the subject. Perhaps as close as inches with a 60 mm, vs. several feet with a 200 mm. Whether this matters depends on the subject. White-faced hornets? I’d go with the 200 mm. Much of my own shooting is done with this 60 mm Nikon.

Extension tubes. These hollow tubes of various lengths move your lens further away from the image sensor, providing more magnification. However, depth of field is even more limited, so I don’t use extension rings in the field. But if you are photographing small items such as seeds indoors, you can use extension rings to get high levels of magnification.

You can obtain finer control over focus using macro focusing rails. I use this one from Adorama, though I would prefer one with finer control. You mount it on a tripod and adjust knobs to move the whole camera forward and backward or side to side. (I don’t know the purpose of the side-to-side option—most rails are just forward and backward.)

If you use Photoshop CS4 or later, or other tools that can do the same thing, you can take multiple photos of an object at different focus settings, then combine all the images automatically into a single, perfectly focused image. This photo of an oak marble gall, about three quarters of an inch in diameter, was assembled from 7 photos using this technique. I don’t think it would be possible to do this without the macro focusing rails, because you cannot adjust the manual focus precisely enough.

Scanning. Plants aren’t generally flat, but a scanner is sometimes useful to obtain detailed images of leaf shape or, say, the seeds on some grass.

Focus. A swaying plant is enough to confound both auto and manual focus—another reason why I take a lot of pictures. If you are shooting with a DSLR, it is sometimes easier to use manual focus than it is to have the focus hunt. Although point-and-shoot cameras have many strengths, manual focus is not among them—there isn’t enough detail in the image or electronic viewfinder to obtain precise focus.

Exposure. The first thing we notice is the flowers, but unless they nearly fill the field of view, the camera will overexpose the flowers because the surroundings are usually much darker. This is especially true in bright sunlight. Set the camera for spot metering to improve upon this, but it is still a good idea to bracket (take several photos at different exposures) to increase your chances of getting a good one. Sometimes I just lower the exposure compensation by a stop to achieve the same end.

Flash. I often favor indirect light—shade, or overcast—to get more even exposures. But motion blur is common in these conditions. So I use flash more and more often. It has several advantages. First, it often helps to isolate the subject, by lighting it more brightly than the background. Second, it helps to freeze motion. Third, images are more likely to have balanced colors. If you shoot macro, though, the flash may illuminate from the wrong angle, unless you have flash designed for use with macro lenses. You can put a diffuser on the flash to make the lighting more even.

If I shoot without flash, I turn the ISO up a bit to help freeze motion, often to 800. If I shoot with flash, I turn it down to 200 (the lowest recommended setting on my camera). This is because I want the flash to be the primary source of light, to minimize motion blur. I also set an obscure option that allows the shutter to operate as fast as 1/320th of a second, again to minimize motion blur.

White balance. Cameras make white balance decisions based on typical scenes. Closeups of plants are anything but typical, and the white balance calculated by the camera is frequently wrong. I shoot raw images and correct the white balance using Adobe Lightroom.

Resolution. I take the highest resolution images I can get. This captures detail that is often essential to an identification, or allows for cropping to emphasize interesting parts of a plant. (Currently the high-res photos on this site are limited to 2000 pixels in height/width, but I will probably remove this constraint in the future.)

Getting the whole plant. I find this to be the hardest part. Once I’ve got the flower, or a curiously shaped seed pod, or some brightly colored berries, I tend to ignore the rest. A positive identification often requires less showy details. Take the time to record those too.

Take lots of photos! I photograph the same species, sometimes even the same plant, repeatedly, to improve the quality of the images or to trace it through its development. Multiple photos really help to make a positive match.

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