Macro autofocus & apertures
QI have recently become fascinated by macro photography and want to produce the kind of images of insects and spiders I have seen others accomplish. I use a Nikon D5300 and have a couple of questions. First, when choosing the best macro lens, would I be better off using a cheaper, used, manual-focus lens, like a Tamron SP 90mm Macro, as autofocus might not be that much use when shooting macro? Second, when focusing as close as possible using my standard kit 18-55 zoom lens, although I’m not getting true macro results I am already seeing that much of the subjects I’m photographing are out of focus. I presume that stopping the lens down to a smaller aperture is the answer, but would that not mean very dark shooting conditions and soft images because of diffraction? My understanding is that you start to lose definition from f/8, while to get everything sharp I might need f/22. Charley Streeter
ARegarding autofocus, if you are focusing on a slow-moving or stationary subject, like a spider, then manual focusing can be easier because you can concentrate on composition. Just move the camera to focus and then use the focusing ring for fine adjustment. On the other hand, if your lens can autofocus quickly and accurately, it can make the job of chasing and capturing subjects that are constantly moving, like bees or butterflies outside feeding on flowers, easier.
When it comes to choosing apertures, you need to trade diffraction resolution loss with depth of field. Happily, the very nature of macro photography means that diffraction does not need to spoil the result even at f/22. This is partly because the details that make a macro shot ‘pop’ are relatively large. We’re also not too familiar with the details we can’t see because of diffraction, so we don’t miss them. Boosting contrast can help and lighting is also very important. This is why some of the most stunning macro photography benefits from the use of carefully positioned lights, often using twin flash or ring flash mounted around the end of the lens.