underwater Photo Course :: (2) Equipment Guide :: Underwater Camera Housings :: Lenses and optics :: Autofocus

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Manual focus of lenses can be slow, inaccurate, and tiring - especially with SLR macroPhotography of smaller subjects shot (between 1:1 and 1:3) on macro settings or with macro equipment photography. autofocusAutomatic selection of the correct focus. TTL focus systems which work through the lens are better for underwater video (AF) lenses automatically focus for you and are faster and more accurate than human reactions.

In many cases, autofocus systems are so sensitive that they can work even when there is not enough light for the human eye to see (so, if they can't see to focus, you certainly can't!). It is not surprising that AF is now the norm.

However, not all cameras have autofocus. Focus must also be achieved by 'guess-timating' on some point and shoot cameras. You must judge the subject distance and relate it to a scale on the lens. However, with a bit of experience you can get quite accurate, especially with wide angle lenses, which are virtually focus-free and for macro photography (the photography of smaller subjects) where the subject area is shown by framers.

An aiming light is a useful accessory to aid AF underwater, it does not need to be strong, a pin-prick of light is all you need!

Autofocus can be a boon for most underwater subjects, and especially useful if you wear glasses. However, some low contrastthe difference in desity between parts of an image. High contrast for example denotes larger differences with blacker blacks and whiter whites. subjects can actually be frustrating to photograph with autofocus as the lens can continually seek, but does not lock on. This is called hunting.