Photography is art. Creativity, light and composition all determine if a photograph is visually successful. Unlike some other art mediums, in photography there are many technical aspects that must be mastered and applied to consistently turn out great images. These are obtaining proper exposure, attaining sharpness, acquiring adequate depth of field, knowing how ISO impacts the outcome, introduction of filters and more. Relative to this week’s tip, macro photography depth of field is critical due to extreme subject magnification. It’s with this in mind that I share the “focus” of this tip to help you better understand what’s required to produce a technically good macro photo.
Depth of field is the distance between the closest and farthest points in the photo that appear sharp. Factors that control depth of field are the focal length of the lens, the working aperture, the distance of the background from the subject, the distance of the foreground from the subject, size of the subject and how much the subject is magnified. Focus is placed at a specific point in the composition. Once set, all the above factors come into play to determine how much focus falls in front and in back of that point. With macro subjects, given very narrow depth of field, all factors are amplified.
The Working Aperture: Wide-open apertures of f/2.8, f/4 and f/5.6 provide the least amount of depth of field. Apertures of f/16, f/22 and f/32 provide the most. If you want to maximize the focus distance, stop the lens down to f/16 or smaller. If you want to minimize depth of field, use the widest setting on your lens.
Focus Point: Depth of field with macro subjects can be measured in millimeters, therefore the focus point is critical. A photo of a bee with a sharp body but out of focus eye fails. It’s essential to place the focus point on the most important part of the subject. To accomplish this, set the camera to manual focus mode, obtain the desired subject magnification and, instead of focusing the lens, carefully move the camera back and forth. When the given point is sharp, press the shutter.
Selective Focus: This technique is used to draw the viewer’s eye to a specific location of the photo. The viewer’s eye will always go to the area within a photo that’s in focus and ignore parts that aren’t. This being the case, use a wide-open aperture and focus on a single plane. Subject matter in back and in front of the focus point will fall out of focus. The result is a sharp section that draws the eye to just that part of the image. A wide-open aperture is often used to accomplish this effect.
Background/Foreground Distance: To successfully create the selective focus technique, you must understand the importance of how subject distance from the background and/or foreground effects depth of field. If the subject is too close to what’s behind or in front of it, it’s impossible to throw either significantly out of focus. The greater the distance between the subject and the foreground/background, the easier it is to create the selective focus look.
Flat Vs. Curved Plane: If a subject is flat and exists on a single plane, wide-open apertures can be used to render everything in focus. But, many macro nature subjects aren’t. Therefore, an aperture that enables the three dimensional surface to fall into focus must be utilized. Stop the lens down to make the image. If necessary, use a small aperture to attain the depth of field. If you get to f/22 and still can’t acquire the necessary depth of field, don’t despair. Back off the zoom, make the photo and crop the image to obtain the desired magnification. In that one aspect of depth of field is dependent upon subject magnification, if it’s less magnified, there’s more inherent depth of field. I’ve used this method, and it works.