Basic Photography Course

Figure 4-10.Direct-vision range finder focusing.

focus knob, until the double images coincide and only

in the direct-vision range finder system. Everything

appears sharp through the viewfinder window.

The disadvantages of a direct range finder system

are that it does not couple to a large variety of lenses,
thus restricting its use to only several different
focal-length lenses. Unlike the ground glass and SLR

focusing systems, depth of field cannot be determined

Autofocus

Most autofocus cameras use the same principle as a

direct-vision range finder camera. The autofocus
camera determines the subject distance by comparing

4-8

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Basic Photography Course

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