PHOTOMICROGRAPHS AND LANTERN SLIDES 
153 
have the white light operated by a switch. With a 40-watt light, 
exposures will vary from 1 to 30 seconds, as the negatives are very 
thin or very dense. With properly exposed negatives, the exposures 
will vary 2 to 5 seconds. 
If you are printing in a printing frame with an average negative 
at a distance of 3 feet from a gas-mantle lamp, try an exposure of 
3 seconds; if the negative is weak, shorten the exposure; if strong, 
lengthen it. If you always use the same light at the same distance, 
you should soon be able to estimate the exposures for negatives of 
various densities. 
If a negative is uneven, the distance from the light may be 
increased so as to lengthen the exposure to several seconds, thus giving 
time to shade the weak parts, just as in case of prints on paper. 
If a negative is harsh and shows too much contrast, hold it closer to 
the light and shorten the exposure; if weak and lacking in contrast, 
hold it farther away and increase the time of exposure. 
Be careful not to underdevelop. A lantern slide looks stronger 
in the developer, and even in the hypo, than it really is. 
2. Reducing and Enlarging.—If a slide is to be made from a 4X5 
or larger negative, there must be a reduction. A camera is necessary. 
A 3i X4J camera is large enough. If any larger size is used, the plate- 
holder must be “kitted” down to 3|X4, the standard size of lantern 
slides in America. In using the larger cameras, mark upon the ground 
glass the exact size and location of the lantern-slide plate. Fasten 
the negative in some convenient place where the light may shine 
through it: diffuse daylight is good. Then arrange the camera just 
as in taking any ordinary picture. The board shown in Figure 29 
will be just as useful in making lantern slides as in making photo¬ 
micrographs. At one end of the board fasten a frame which will hold 
an 8X10 negative and also hold kits for smaller negatives (Figs. 29 B 
and C). The long slot in the board will allow the camera to be 
fastened at the proper distance. If buildings, trees, or shadows 
are in the way, tilt the board so as to have a clear sky for a back¬ 
ground. 
Be very careful in focusing; it is best to examine, with a pocket 
lens, the image on the ground glass. In general, use a rather small 
stop, F16 or even F32. If reducing from an average 5X7 negative, 
in good daylight, with an FI6 stop, try 2 or 3 seconds. If enlarging 
from a negative somewhat smaller than a lantern slide, try 8 or 10 
