The American annual of photography . The difference between the lowest and higheststeps (ab) or density contrast is very small. On prolongeddevelopment each step has increased in density, and the densitycontrast (cd) is much greater than (ab). The density contrast of a negative is governed both by thedifference in brightness between the high lights and shadowsof the subject and by the degree of development of the nega-tive. In order therefore to maintain the density contrast of abatch of negatives as constant as possible, films exposed on aflatly lighted subject should be fully developed, but
The American annual of photography . The difference between the lowest and higheststeps (ab) or density contrast is very small. On prolongeddevelopment each step has increased in density, and the densitycontrast (cd) is much greater than (ab). The density contrast of a negative is governed both by thedifference in brightness between the high lights and shadowsof the subject and by the degree of development of the nega-tive. In order therefore to maintain the density contrast of abatch of negatives as constant as possible, films exposed on aflatly lighted subject should be fully developed, but those ex- 196 posed on a contrasty subject should be developed to a lessextent. Density contrast should be carefully differentiated fromgeneral density. An over-exposed and under-developed nega-tive will have good density in the shadows, but the high-lights will not be much more dense; that is, the negative as awhole will look dense but the density contrast will be maximum density contrast is the greatest density contrast. Figure 4,Showing the Growth of Density of the Image During Development. obtainable by prolonged development until fog begins to format a greater rate than the image. As regards maximum density contrast and speed of develop-ment, developers fall into four classes as follows : (a) High maximum contrast and high speed of develop-ment; that is, the negative rapidly obtains great generaldensity and contrast. In terms of the step negative (Figure2, page 192), the density of h is fairly high and the density dif-ference g-h is great also. Developers of this type are Elon-hydroquinone or pyro developers in combination with causticalkali. (b) Low maximum contrast and high speed of developers are of this type; that is, the image flashes upbut fails to build up general density. In terms of the step 197 negative, the density of b is fairly high, but the dififerenceg-h is comparatively small. (c) High maximum contrast and low speed of development
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1922
