The Canon AL-1 was an FD mount, 35mm single-lens reflex camera introduced in March 1982. Its main feature was the "Quick Focus" focus-assist system that was aimed at those who had trouble focusing through the viewfinder—either novices, or those with poor eyesight—and was intended to head off competition from the first full-autofocus cameras from other manufacturers, such as the Pentax ME-F.
The QF focus-assist system searches for the greatest ima...
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The Canon AL-1 was an FD mount, 35mm single-lens reflex camera introduced in March 1982. Its main feature was the "Quick Focus" focus-assist system that was aimed at those who had trouble focusing through the viewfinder—either novices, or those with poor eyesight—and was intended to head off competition from the first full-autofocus cameras from other manufacturers, such as the Pentax ME-F.
The QF focus-assist system searches for the greatest image contrast in the subject using three linear CCD arrays in the base of the camera. Light is diverted to these sensors through a partially-silvered mirror. When the contrast in the image is greatest, the image is the least blurred and thus in focus. Below the viewfinder image, two red arrows indicated which direction to turn the focusing ring to achieve focus, which is indicated by a green circle lighting in between the two arrows. Contrast detection is the system used for autofocus on most compact digital cameras in recent years.
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