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378 PHOTOGRAPHIC ENLARGEMENTS [Cn. X
FIG. 216. GOTHIC TYPE TO USE ON DRAWINGS AND THE APPEARANCE WHEN REDUCED.
In the upper half are shown letters and figures of full size with their designations by the printer, i. e., 24, 18, 12, 10, 8 and 6 point type.
In the lower half are shown the same reduced to one-half the length, and reduced to one-fourth the length.
shown by the numerals and letters in fig. 216, if the drawing is not to be reduced at all one can use 6, 8, or possibly 10 point type. For one-half reduction (one-half -off) , the lettering should be with 10 or 12 point type. For one-fourth size ($4 off), then the lettering should be with 12 or preferably with 18 point type.
PROJECTION APPARATUS FOR PHOTOGRAPHIC ENLARGEMENTS
§ 532. Enlarged prints of negatives. — There is great advantage in making pictures of large objects at a considerable distance so that the perspective will be correct and all levels in focus. It is also advantageous to make pictures of microscopic objects without undue enlargement, then there is greater sharpness of the object as a whole.
If now one wishes a large picture, any good negative can be printed by the aid of a photographic objective at almost any desired enlargement. This can be done with projection apparatus in a dark room by the following method : The management of the projection apparatus is as for drawing. The negative is placed in some kind of a holder and put in the cone of light from the main condenser where the part to be enlarged will be fully illuminated (fig. 132, 185). Care must be taken to so place the negative that an erect image will appear on the printing paper (§ 512).
§ 533. Condenser required with negatives of different sizes. —
Remember that the diameter of the condenser must be somewhat greater than the diagonal of the part of the negative to be enlarged (§314 and fig. 114). For example, to use the whole of a lanternslide negative (85 x 100 mm., 3^ x 4 in.) the condenser should have a diameter of 14 cm. (5^2 in.).
For a negative 100 x 125 mm. (4 x 5 in.), the condenser should beiScm. (7 in.) in diameter; fora negative 125 x 175 mm. (5x7^1.), the condenser should be 23 cm. (9 in.) in diameter and for a negative 200 x 250 mm. (8 x 10 in.), the condenser should be 35 centi