US746594A - Isochromatic photographic plate and film. - Google Patents

Description

NQ. 746,594. PATENTED DEG. a, 1903.'

L. SMITH. N

ISVDGHROMATIC PHOTOGRAPHIG PLATE AND FILM.

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*UNiTED ISTATES,

Patented December 8, 1903. f

'PATENT OFFICE.

LEONARD SMITH, OF LONDON, ENGLAND.

SPECIFICATION forming part of Letters Patent N o. 746,594, dated December 8, 1903.

Serial No. 146,207. (No model.)

To a/ZZ whom it may concern:

Be it known that I, LEONARD SMITH, manufacturing chemist, a subject of the King of Great Britain, residing at 14 West Hill, Highgate, London, England,have invented certain new and useful Improvementsin Isochromatic Photographic Plates and Films, of which the following is a specification.

As is well known in photography, the tonerendering and modeling qualities of the ordinary sensitive emulsion are extremely imperfeet, and one method of correcting this defect is by treating the emulsion with organic dyes, whereby the sensitiveness of the emulsion to the red, green, and yellow rays is greatly increased; but such an emulsion does not afford an improved tone-renderin g when the subject exhibits contrasts; and the present invention has for its object to produce an isochromatic color-sensitive film whereby a more perfect modeling and a more correct color-rendering may be obtained.

In the accompanying drawing, forming a part of this specification, the figure represents asectional view of a support and the ilm carried thereby.

In order to accomplish the desired result, a suitable support C is employed,on which is arranged the film, consisting of two or more superimposed color-sensitive emulsions B A of progressivelyvarying degrees of sensitiveness and color sensitiveness, so that when the composite rays fall on the topmost layer of most highly color-sensitive emulsion the latent image will be formed in that layer, and as the exposure is continued the most powerful rays, or those which produce the extreme high lights, alone will penetrate to a greater depth. In the case of an ordinary film these rays would spread over the sensitive emulsion, thereby impairing correct tonal relation, and, moreover, part of these rays would be reiiected by the surface of the support by which the sensitive film is carried and would thereby cause halation, whereas in the case of a sensitive iilm made according to thisinvention the presence of the less sensitive coating or coatings of color-sensitive emulsion underlying the layer first acted on will have the effect of causing these harmful rays to be absorbed. Even underprolonged exposure the complete penetration of the composite rays will be prevented and correct tonal relation will be maintained in the several superimposed layers of colorsensitive emulsion. Thus the correct relative value of all tones in the negative will be preserved and no rays will be permitted to pass completely through the composite film composed of several superimposed layers of sensitive emulsion.

In carrying theinvention into eect the two emulsions are to be rendered color sensitive by a definite percentage of the potassium salt of tetraiodid of iiuorescin and the proportions of which are different in the slow and fast emulsion, the quantities being in the fast film for every one hundred parts of silver bromid .12 parts and in the slow film .O6 parts. The sloweremulsion having ,been applied as a first layer B on the support C and dried, the faster emulsion, made in the same manner, but diering from the rst only in its higher degree of sensitiveness to the actinic rays, is then applied as a second coating A on top of the first or slower coating and allowed to dry, and so on for as many superimposed coatings of progressively-increasing degrees of sensitiveness as may be deemed necessary to insure the complete interception of the rays. A

I am aware that a lm composed of a single layer of isochromatic emulsion and a film composed of two or more superimposed layers of ordinary non-isochromatic emulsion are known, and I do not lay any claim to either separately. v

The advantages obtained by this invention as compared with the ordinary single layer of isochromatic emulsion is the absence of all halation and false tone-rendering due to imperfect interception of light-rays and as cornpared with a double or triple layer of ordinary emulsion the wider and more perfect tone-rendering due to the color sensitiveness of each layer of emulsion of which the film of this invention is composed.

I claiml. As a new article of manufacture, an isochromatic photographic lmformed of successively-superimposed layers of color-sensitive emulsion having progressively-varying degrees of sensitiveness and color-sensitiveness, as speciied. y

2. As a new article of manufacture, an iso- IOO chromatic photographic film formed of sucunderlying slow lm 'containing the lesser` cessively-superimposed layers of color-sensiand the superimposed faster film the higher tive emulsion. having progressively-varying percentage of the said salt, as specified.

degrees of sensitiveness, and which have been LEONARD SMITH. 5 rendered color sensitive by the incorporation Witnesses:

therewith of the potassium sait of tetraiodid C. G. CLARK,

of fiuorescin, in different proportions, the 1 T. W. KENNARD.

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