Contrast monitor

A light exposure meter which comprises a photocell, three light emitting diodes (L.E.D.'s) and a control means which can be actuated to cause a first L.E.D. to glow when the photocell receives light, means to cause a second L.E.D. to glow when the photocell receives light of a greater level than that received by it when the first L.E.D. was caused to glow, means to cause the third L.E.D. to glow when the photocell receives light of a lower level than that received by it when the first photocell was caused to glow, a rotatable disc carrying around its periphery a graduated set of six neutral density filters, the disc being so located that each filter in turn can be placed over the photocell, but there being at least one point in the rotation of the disc when the photocell can receive light directly from a light source without a neutral density filter being interposed.

A light exposure meter which comprises a photocell, three light emmitting diodes (L.E.D.'s) and a control means which can be actuated to cause a first L.E.D. to glow when the photocell receives light, means to cause a second L.E.D. to glow when the photocell receives light of a greater level than that received by it when the first L.E.D. was caused to glow, means to cause the third L.E.D. to glow when the photocell receives light of a lower level than that received by it when the first photocell was caused to glow, a rotatable disc or a strip carrying a length of neutral density filter of increasing optical density, the disc or strip being so mounted that each area of different density can be placed over the photocell, and each area having been calibrated to correspond to the log exposure scale of the normally used grades of paper, but there being at least one point in the rotation of the disc or in the lengthwise movement of the strip when the photocell can receive light directly from a light source without any part of the neutral density filter being interposed.

A light exposure meter which comprises a photocell, three light emmitting diodes (L.E.D.'s) and a control means which can be actuated to cause a first L.E.D. to glow when the photocell receives light, means to cause a second L.E.D. to glow when the photocell receives light of a greater level than that received by it when the first L.E.D. was caused to glow, means to cause the third L.E.D. to glow when the photocell receives light of a lower level than that received by it when the first photocell was caused to glow, a solid rotatable disc of decreasing diameter such at the point of its greatest diameter the photocell is completely covered by the disc and at the point of its smallest diameter no part of the photocell is covered by the disc whilst varying amounts of the photocell are covered by the disc as it is rotated between these two points and each segment of the periphery of the disc having been calibrated to correspond to the log exposure scale of the normally used grades of paper.

A light exposure meter which comprises a photocell, three light emitting diodes (L.E.D.'s) and a control means which can be actuated to cause a first L.E.D. to glow when the photocell receives light, means to cause a second L.E.D. to glow when the photocell receives light of a greater level than that received by it when the first L.E.D. was caused to glow, means to cause the third L.E.D. to glow when the photocell receives light of a lower level than that received by it when the first photocell was caused to glow, a rotatable disc or a lengthwise movable strip which comprises a slit of varying width which partially covers the photocell and which can be moved over the photocell to cover increasing or decreasing amounts of the photocell and each portion of the slit having been calibrated to correspond to the log exposure scale of the normally used grades of paper, but there being at least one point in the rotation of the disc or in the lengthwise movement of the strip when the photocell can receive light directly from a light source without any part of the photocell being covered by the disc or the strip.