Depth-of-field preview apparatus for a single lens reflex camera

摘要

A depth-of-field preview apparatus for a single lens reflex camera is provided with a display circuit responsive to a preview display signal generated by a control circuit with at least one of first and second switches being closed. The first switch is closed when an operating member is operated to an operated position and opened when the operating member is released to return to a non-operated position under a spring bias. In response to the closure of the first switch the control circuit generates the preview display signal and an electromagnetic device causes a diaphragm stop-down mechanism to stop-down a diaphragm. When the diaphragm is stopped-down to a preset aperture size, another electromagnetic device stops the diaphragm stop-down mechanism to set the diaphragm to the preset aperture size and at the same time closes the second switch. With the second switch being closed the control circuit continues to generate the preview display signal independently of the condition of the first switch, so that a preview display by the display circuit does not cease even if the operating member is released and accordingly the first switch is opened.