Definitions

Focus_free_lens

Focus free lens

A focus free lens is a photographic lens whose focal point is fixed at its hyperfocal distance. Rather than having a method of determining the correct focusing distance and setting the lens to that focal point, a focus free lens relies on depth of field to produce acceptably sharp images. Most cameras with focus free lenses also have a relatively small aperture which increases the depth of field. Cameras with these lenses generally use a viewfinder for composition.

The advantage of this design is that it can be produced very inexpensively, more so than automatic or manual systems. The system is also effectively automatic; the photographer need not worry about focusing. It can also be more predictable than automatic systems.

Some disadvantages are that this type produces images that are less sharp than a lens that has been set to the best focal point for a given scene, and they are unable to produce sharp images of objects close to the camera, usually within 8-12 feet. The latter limitation makes them unsuitable for portraits, as they cannot fill the frame of an image with a person's face and render it sharp at the same time. This limitation is likely to confuse inexperienced photographers.

Focus free lenses are used in the lowest-end and cheapest cameras; disposable and low-end point and shoot cameras. They are usually wide angle with fixed aperture.

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