The following article is an excerpt from The Complete Guide to Macro and Close-Up Photography by Cyrill Harnischmacher.
Along with lighting, depth of field is one of the key limitations for macro photographers. Depending on the magnification, it can drop down to millimeters or even tenths of a millimeter. One mistake that beginning macro photographers often make is paying too much attention to the positioning of the subject itself and not enough attention to its background with regard to how it figures into the overall composition. Not attending to the background thoughtfully may result in images where the subject doesn’t pop out sufficiently or where too many distracting details clutter the image area. Pay attention to all of the elements within your image, and pay special attention to the extent to which each of these elements is located within the depth of field.
Positioning the Focal Plane
When working with a wide-open aperture, the focal plane effectively represents the entire functional depth of field. When photographing insects and other small animals, it’s important to position the focal plane on the subject’s eyes. Any photo with a subject’s eyes out of focus will be interpreted as a mistake.
When working with abstract subjects, the question of where to position the focal plane is less straightforward. In these cases, determine what part of the image should carry the added significance of appearing sharp. Once you’ve settled on that, you may want to use the rule of thirds or the golden ratio to finish composing your image. In some cases, it may be valuable to sacrifice some depth of field for the purpose of realizing a specific intention.
Layers of Depth
Composing an image to feature layers with varying degrees of sharpness profoundly increases its spatial depth. Objects aligned along a diagonal and sequences of repeating identical or nearly identical elements tend to underscore this effect.
The properties of a lens determine the aesthetics of an image’s blur, or its bokeh. The look and feel of the transition areas between what appears sharp and what does not technically is determined by the number and orientation of the aperture blades along with the selected f-stop. In more compositional terms, the positioning of specific elements within the image area plays an important role in the appearance of blur. Other factors including the source and intensity of the lighting also come into play. For example, you can influence the quality of an image’s blur by lighting the background in a certain way or using as diffuse light as possible to alter the atmosphere of the scene.