In a number of past issues, do :: or :: diso tackled how to emphasize the subject – make it pop, in post processing, create tonal differences between the subject and the background, and think background, background, background. This, month do :: or :: diso gets all techno crazy in a discussion of compression, bokeh, and depth of field. All three can work together to emphasize the subject.
Let’s start with compression and some dictionary definitions:
- Compress – to flatten by pressure; squeeze; or press ; to reduce in size, quantity, or volume as if by squeezing.
- Compression – the action of compressing or being compressed.
When we squeeze the shutter, we really do not flatten, squeeze, or press anything, at least not in the traditional sense. But, when we use a telephoto lens, or a zoom lens at telephoto range, we do affect the scope of something in both size and volume. The subject of the image is is brought closer and fills the frame, and thereby we increase the size of the subject relative to our eye. So, the subject seems bigger, not reduced in size. But something is indeed reduced – the field of vision.
These images will depict that field of vision reduction.
Thus, a wide angle lens “sees” more – think of it as an expansive or spread-out, sweeping view of the background – the stuff behind the subject. A telephoto lens “sees” less – it simply takes in less of the stuff behind the subject. Think of it as restricted,and narrower. When the eye looks at the image, it will take in everything captured in the image. The eye will scan the background, sorting out the “stuff” in the photo and eventually, drawing its attention to the subject matter. The less that is depicted, the more the eye is drawn to the subject.
Compare these two shots:
In the second shot, the eye goes right to the quarterback. In the first shot, it takes a while to find the ball carrier. Nothing wrong with the second shot. It does offer a sense of the size of the stadium and the moment (the 2015 Division 2 NCCA football championship) but the first shot takes you right to the quarterback.
- Bokeh – a japanese term for the subjective aesthetic quality of out-of-focus areas of a photographic image.
Bokeh is simply the creation of a blurry background, and is easily achieved by a wide-open aperture. As Paul Davies notes: “in fact, bokeh becomes a consideration anywhere where shallow depth of field eliminates background clutter and emphasizes the sharpness of the subject.”
The effect of bokeh is two-fold – a pretty background wash, and the viewer’s eye is drawn to the in-focus subject of the image.
Last, depth of field. The Photographic Society of America definition:
- depth of field – depth of field refers to how much is in focus in front of and behind the subject that is focused upon. “more” depth of field means that more is in focus. “shallow” depth of field means that very little is in focus other than the subject.
The camera lens mimics the human eye — while other factors affect our depth of field, when your pupil is contracted, as in bright sun light, your depth of field increases. Similarly, depth of field in your camera is largely dependent on the aperture you or your conditions choose. To illustrate this, you can go to a number of web sites that will calculate depth of field for you once you provide the focal length, aperture and distance to your subject. To illustrate this, here are 3 calculations using a wide open 500mm length (super telephoto wide open at its f / 4.0 maximum aperture), a 200mm length (the longest in a 7-200mm telephoto lens wide open at its f / 2,8 maximum aperture) and 40mm (right in the middle of a 24-70mm wide angle wide open at its f / 2.8 maximum aperture).
In each instance the subject is 40 feet away (about 13 yards). The difference in depth of field is startling: for the 500mm lens, .23 feet behind the subject (2.7 inches), the picture loses its focus. For the 200mm lens, 1.04 feet (12 inches) behind the subject the picture loses its focus. And, for the 40mm shot, a remarkable 72.5 feet behind the subject, the picture loses its focus. The difference in depth of field between the super telephoto lens and the wide angle lens is an astounding 72.27 feet behind the subject!
What does all of this mean to the sports photographer? To borrower again from Paul Davies, each of these offer a compositional element that “makes us consider the parts of an image that are not in focus and are separated from the main subject. These blurred [and compressed, small angle of view] areas have often been dismissed as ‘just the background’ by those who don’t know any better. However, experienced photographers realize the background has a significant psychological impact in setting the mood of a shot and, in a practical sense, can enhance the apparent sharpness of the subject, or otherwise accentuate it through contrast in color and texture.” In other words, to achieve separation of the subject from the background, that all-important element in sports photography, your use of a wide open aperture with a telephoto lens will narrow the depth of field, blur the background, give you bokeh, and reduce the field of vision. Combined, you will have a subject that is enhanced by the background, and not a background that will distract from the subject.
The challenge of this combo: you really need to nail the focus point. There is little margin of error. But, when it clicks, it is a more than satisfying result.
Next month, do :: or :: diso gets all philosophical and asks: should your pictures tell the whole story?