430 HANDBOOK OF PHOTOGRAPHY 



If incorrectly placed, the light will cast upon the easel only a small circle of intense 

 light; the rest of the negative will not be covered properly and the enlargement will 

 show these light variations clearly. 



If a negative is dense and it is difficult to get accurate focus, a useful expedient is 

 to place in the negative holder a well-fogged negative on which fine scratches in the 

 emulsion have been made. When these scratches are sharply defined on the easel, the 

 test negative is in focus and may be replaced by the negative to be enlarged. 



Equipment for working with miniature negatives will usually produce enlargements 

 up to 15 or 20 diameters with the physical equipment built into the enlarger. If still 

 greater magnifications are desired, some means must be found for increasing the 

 distance from lens to paper. Usually, sufficient adjustment of the lens-to-negative 

 distance is built into the enlarger so that its enlarging ability is beyond the limit set 

 by the lens-to-paper distance. This is generally accomplished by placing the paper on 

 the floor and by turning the camera so that the rays of light from the objective clear 

 the table upon which the camera stands. With enlargers adapted for negatives of 

 large size, e.g., 3J^ by 414 in. and up, magnifications much greater than four or five 

 diameters are not possible because of the considerable lens-to-easel distance required. 

 The only solutions in this case are to use a lens of shorter focus or to use an accessory 

 lens to reduce the focal length of the objective. 



Enlargers for miniature negatives may use lenses of 50 to 100 mm. focal length. 

 Present-day equipment is constructed on the vertical plan, the camera extending 

 up in the air, the easel being below it and horizontal. Vertical space is seldom at a 

 premium in the darkroom, and a horizontal easel is much easier to work with. 



Certain older equipment had other adjustments in addition to those mentioned. 

 For example, the negative might be tilted, or swung about a vertical pivot through the 

 center of the negative, or the negative might be raised or lowered so that one portion 

 could be brought nearer the center of the rays from the light source. Modern equip- 

 ment has few or none of these additional adjustments. If one edge of the easel is 

 tilted with respect to the negative, certain correction in the lines of the negative may 

 be effected. For example if the lines of a building converge because the camera 

 has been tilted in making the original exposure, the easel may be tilted in the opposite 

 direction. In general, however, modern enlarging practice has little need of these 

 additional adjustments. 



Most modern equipment includes a yellow or red filter which may be swung into 

 the beam from the lens to make it possible to focus directly upon the sensitive paper. 

 When the exposure is to be made, this filter is removed from the light beam. 



Condenser Enlarger. — This type of equipment is useful when the utmost sharpness 

 of detail is desired, or when the maximum use of the light source must be secured. 

 Because of this sharpness of detail, flaws in negatives are not subdued at all in enlarging 

 so that retouching on negatives to be projected must be much more carefully done than 

 if the enlarged print is to be made by a diffusion system. 



In condenser equipment, rays of light are scattered more in the heavier portions 

 of the negative than in the less dense portions. The latter go straight through the 

 negative and are collected by the projection lens. Some of the scattered rays, how- 

 ever, are not collected by the lens and do not reach the printing paper. For this 

 reason, the contrast of prints made by a condenser system is greater than prints made 

 by a diffusion system. This is known as the "Callier effect." Placing a simple 

 diffusing medium between the light source and the negative will eliminate this effect, 

 but the advantage of the condensing system is lost. 



The details of a condenser system are shown in Fig. 10. Theoretically, if the illu- 

 minant is a true point source, the condenser lens brings the rays that pass through 

 it to a focus in the center of the projection lens. If the lens is moved farther away from 



