Macro photography is a different world. It’s amazing what things look like when you really get in really close. It takes a practiced eye to spot good compositions when looking at a greenhouse full of plants, particularly when looking for composition of several inches or less.
The other challenge with macro work is depth of field. Even with small apertures, the depth of field is amazingly small. For example, with my 100mm lens set to f/16, if I’m shooting from 10 feet (3 meters) away from my subject (which I normally wouldn’t do for macro work, normally I’d be much closer), the depth of field is 1.81 feet (55 centimeters). However, if I am shooting from only 1 feet (30.5 centimeters), a much more typical distance when doing macro work, the depth of field at f/16 is only 0.15 inches (3.8 millimeters). Move 25% closer, to 0.75 feet (22.9 centimeters), and the depth of field drops more than 50%, to 0.07 inches (1.8 millimeters). (I used the equations provided by DOFMaster for these calculations. The DOFMaster website also contains a convenient, on-line depth of field calculator for larger working distances.)
The extremely small depth of field makes focusing very critical – you purposely need to think about where to focus and how the composition will look with potentially large areas of the frame out of focus. If you try this type of photography, play around with your aperture to see what different results you can get (as I’ve mentioned in an earlier post, I’m an habitual bracketer, including bracketing by aperture). By choosing a large aperture, you can force most everything out of focus to create more “artsy” images. Or go for a larger depth of field with a small aperture (though with very small apertures, you lose sharpness as well; though my macro lens goes down to f/32, I almost never use that aperture because it is so unsharp). If you want a wider depth of field that even a small aperture can’t give, you may have to give up magnification and back up from the subject to increase the depth of field.
In macro photography, your subject needs to hold still. Even using fast shutter speeds to freeze movement, this is true because of the limited depth of field. It’s very easy for a flower moving in the breeze, or a wandering bug on that flower, to move outside the depth of field. This is why I am so impressed with all those photographers who get great macro shots of insects. That’s why, as a relative beginner to macro work, I like working with plants – they don’t move on their own accord. A conservatory makes it even easier, no natural breezes to deal with.
