Incident light filter for cameras

Claim 1

In combination with a single-lens reflex camera having a through-the-lens built-in light metering facility including light-sensitive cells and a lens assembly for admitting light to activate said light metering facility and for focussing an image of a photographic subject on film within the camera, a transluscent image-blocking device detachably secured in front of said lens assembly whereby approximately 18% of the light from a source thereof impinging on said translucent image-blocking device passes therethrough and through said lens assembly to activate the light sensitive cells in said built-in light metering facility whereby adjustments of the exposure controls of the camera may be set after which said translucent image-blocking device is removed to permit the image of the photographic subject to pass through the lens assembly when the subject is photographed, a lens plate juxtaposed to said transluscent image-blocking device and including a flat surface facing the source of light and a light transmitting prismatic surface next adjacent the trnasluscent device and adapted to transmit light thereto, a filter member formed from thin transluscent sheet material interposed between the transluscent device and the lens plate, and a mounting ring surrounding said transluscent device, said lens plate and said filter member and retaining said components in a composite assembly for attachment to the lens of the camera.