Color correction method for panchromatic printing and its device

Claim 2

In a method for making panchromatic prints from a panchromatic negative film by the subtractive process, the steps comprising: passing a white light through a panchromatic negative film; mixing up uniformly by means of a diffuser said passed white light; passing said mixed up light through first, second and third side-by-side filters respectively of first, second and third subtractive primary colors, each of said first, second and third filters being graded in several steps from relatively low to relatively high density; performing panchromatic printing with the light passed by said filters and producing a test color print carrying for each of said first, second and third subtractive primary colors a series of color sections stepped in decreasing color intensity down to a least visible section, wherein the number of visible sections may differ as between said first, second and third colors; detecting the number of visible sections by which the series with the fewest visible sections is exceeded by each of the other two and with these numbers selecting color correction filters.

Claim 3

Method of claim 1, in which said step of passing light through said filters includes arranging the graded filter steps for each color in a row, arranging the rows for said three subtractive primary colors side-by-side, and arranging a fourth row of neutral density steps side-by-side therewith and passing of said mixed up light through said four rows of graded density steps of first, second and third primary colors and neutral density, respectively, color and neutral steps of equal density being arranged side-by-side transversely of said rows, said step of detecting including finding the shortest of the three color step rows on the test print and counting the number of visible steps extending therebeyond in each of the other two color rows.

Claim 4

The method of claim 2, in which said step of passing light through filters includes passing of light through red, green and blue-violet filters.

Claim 5

A color correction device, comprising: first, second and third color filter strips respectively of first, second and third primary colors, each of said first, second and third filter strips having substantially uniform color density throughout its length, said first, second and third color filter strips being arranged side-by-side in nonoverlapping relation; a neutral density wedge in superposed relation with each of said first, second and third color filter strips, each neutral density wedge including a series of increasing density steps distributed progressively along the length of its corresponding color filter strip, the number of color density steps for a given one of said first, second and third colors being the number of neutral density wedge steps in said superposed relation with said color filter strip; substantially opaque pattern sheet means in superposed relation with said first, second and third color filter strips and also with said neutral density wedge of each thereof, said pattern sheet means having light transmitting sections superposed on corresponding wedge steps for each of said first, second and third color filter strips and thereby providing a row of light transmitting sections for each said color filter strip, said color filter strips, neutral density wedges and pattern sheet means being superposed as a single unit.

Claim 6

A color correction device, comprising: first, second and third color filter strips respectively of first, second and third primary colors, each of said first, second and third filter strips having substantially uniform color density throughout its length, said first, second and third color filter strips being arranged side-by-side in nonoverlapping relation; a neutral density wedge in superposed relation with each of said first, second and third color filter strips, each neutral density wedge including a series of increasing density steps distributed progressively along the length of its corresponding color filter strip, the number of color density steps for a given one of said first, second and third colors being the number of neutral density wedge steps in said superposed relation with said color filter strip; substantially opaque pattern sheet means in superposed relation with said first, second and third color filter strips and also with said neutral density wedge of each thereof, said pattern sheet means having light transmitting sections superposed on corresponding wedge steps for each of said first, second and third color filter strips and thereby providing a row of light transmitting sections for each said color filter strip, said color filter strips, neutral density wedges and pattern sheet means being superposed as a single unit.

Claim 7

A color correction device according to claim 4, including a further density wedge laterally offset from said superposed color filter strips and having density steps corresponding to those of said neutral density wedges superposed with said color filter strips, both as to density and extent along said rows, said pattern sheet means including a further row of light transmitting sections superposed on said steps of further density wedge, for determining density.

Claim 8

A color correction device according to claim 4, in which said neutral density wedges differ from each other in transmitting density in correction for differences in transmitting density between the said first, second and third color filter strips, the combined density of color strip and neutral density wedge step at a given light transmitting section superposed on said first color filter strip being substantially identical to the combined density through an adjacent section superposed on said second and third color filter strips, despite differences in density as between said first, second and third color filter strips.

Claim 9

A color correction device according to claim 4, in which said color filter strips are straight and lie in close spaced parallel relation to each other, said neutral density wedge steps for each color strip accordingly being disposed in a straight line, said rows of light transmitting section similarly being straight.

Claim 10

A color correction device according to claim 4, in which said color filter strips are disposed side-by-side in one layer, said neutral density wedges are disposed side-by-side in another layer and said pattern sheet means provides still another layer, and further comprising, in order, a protective transparent layer, an opaque mask layer with elongate light transmitting windows extending substantially the width and at least the length of said rows of said pattern sheet means, and a further transparent protective layer, said layers being arranged in the order of said first mentioned transparent protective layer, said mask, said color filter strip layer, said neutral density wedge layer, said further protective transparent layer and said pattern sheet means layer and secured in snugly stacked relation to form a color scale of platelike form.

Claim 11

A color correction device according to claim 4, including a color scale of multilayer platelike form in which said color filter strips comprise one layer, said neutral density wedges another, and said pattern sheet means another, said color correction device further including a base, a cover mounted on said base for opening and closing, said cover having an open central portion fixedly occupied by said color scale, said base having an upper surface for supporting a piece of panchromatic print paper directly and snugly beneath the cover closed position of said color scale.

Claim 12

A color correction device according to claim 9, in which said base incorporates a wide area but vertically thin slot in a portion of said base below said upper surface, said slot opening sidewardly from said base for receiving therein a width of paper corresponding to the width of said color scale, said body at the opening of said slot including a knife guide for cutting off a piece of photographic paper entering said slot at a width corresponding to the depth of said slot, for use as a test paper to be disposed beneath the cover.