# US 5,353,080 A · Exposure-equalizing system for photographic images

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- Number: US 5,353,080 A
- Document ID: US5353080A
- Status: Granted
- Kind: A
- Application number: 07/970,042
- Filed: 1992-11-02
- Granted: 1994-10-04
- Earliest claimed: 1992-11-02
- Inventors: Ernest H. Christman
- Web page: https://patentgrep.com/patent/US5353080A

## CPC

- G03B 7/08: Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
- G03B 7/09971: {in mirror-reflex cameras (G03B7/09979 takes precedence)}
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A transparent photochromic medium is placed before the film or film-equivalent of a camera or photographic imaging device such that a light exposure of the medium temporarily darkens it according to the different light values in the image. A subsequent exposure of the film is influenced by the intervening photochromic device so that the range of light is moderated, reducing over- and under-exposure of areas of the film.

## Claims

### Claim 1

An image control device in a photographic apparatus comprising:
(a) a transparent photochromic medium that is interposed in the internal optical path, and
(b) a mirror before said medium that transmits light coming from anterior to posterior but reflects light coming from posterior to anterior, and
(c) a mirror behind said medium that reflects light forward, and
(d) the mirrors in multiple parts which fit together into the optical path when brought together, and
(e) the photochromic medium in multiple parts which fit together into the optical pathway when brought together.

### Claim 2 (depends on 1)

The image control device of claim 1 wherein said device is incorporated in the optical path of photographic apparatuses, comprising:
(a) cameras,
(b) video cameras,
(c) image projectors,
(d) photographic enlargers, whereby the range of light value contrasts of a subject image on a photorecording medium is reduced by transmission through the photochromic medium which has had prior exposure to said subject image.