| 摘要 |
847,920. Photographic materials. GEVAERT PHOTO PRODUCTEN N.V. Aug. 24, 1956 [Aug. 25, 1955], No. 25997/56. Drawings to Specification. Class 98(2) A multi-contrast material comprises two lightsensitive silver halide emulsions, one of which is sensitive to a part of the spectrum to which the other is insensitive and one emulsion has a higher contrast but a lower sensitivity to white light than the other. The emulsion of higher contrast may be sensitive to a part of the spectrum to which the other emulsion is insensitive and in Examples 1 and 2 a high contrast orthochromatic bromide or panchromatic chloride emulsion is applied to a film support having an anti-halation layer under an optically unsensitised emulsion of normal gradation (y=1) and of ten times greater sensitivity to white light. The material may be exposed to white light alone but an exposure to white light followed by an exposure to yellow light of the appropriate duration ensures that the high-lights are recorded by the yellow light in the higher contrast emulsion. Alternatively, a high contrast optically unsensitised emulsion is less sensitive to white light than an orthochromatic bromiodide emulsion of softer gradation so that the contrast of the shadow detail recorded in the orthochromatic emulsion can be varied by varying the proportion of the exposure given by yellow light. The emulsions are developed in a N-methyl-para-aminophenol developer of specified composition. The emulsions may alternatively be coated in a different order or on opposite sides of the support or the emulsions may be mixed before coating. |
