Hyperactive Apertures
The basic idea behind depth of field is that wide apertures mean less in focus and small apertures mean more in focus. So, for portraits we often use a wide aperture and with landscapes a small one. Even with a small aperture you may be wasting depth of field beyond the infinity focus point where it does no good at all. Imagine it is a blanket hanging over the end of your bed. If your chest is cold, simply pull the blanket up. The same principle can be applied with depth of field.
Some lenses have markings that will let you bring that wasted depth of field forward and thus bring your foreground more into focus. These marks are sometimes found between the aperture settings and the focus markings on a lens. Simply close your lens to the smallest aperture possible or practical and reset the focus so that the infinity marking agrees with your aperture setting on these markings as seen in these photos. By bringing your depth of field forward, you are focussing on a point known as the ‘hyperfocal distance’, which uses depth of field to cover the rest and make everything sharp. For those with lenses which do not have hyperfocal settings, there is another answer. A less accurate but easier method of employing hyperfocal distance is to close your aperture to the smallest setting and focus about one third into the picture.This is by no means intended as a mathematical structure to ensure absolute sharpenss throughout. Its just a guideline, but a pretty good one. Almost invariably this will cover you if you are using a wide angle lens and f22 or smaller. With digital it may not even have to be as small as f22 as the smaller sensors in cameras these days mean that depth of field for any given aperture is more than with 35mm film.
Shelton Muller is a professional photographer based in Melbourne Australia. He can be contacted via his website at www.photographybyshelton.com
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