out until its distance from the negative is but little less
than its distance from the screen. To make the enlargement greater we
simply rack back the lens and move the screen further off. There are
tables which show exactly the distance which the lens must be from the
negative and screen in order to get an enlargement of a given size: The
table here inserted covers the ordinary requirements and may be of service
in constructing the apparatus:

TIMES OF ENLARGEMENT

Total distances from the negative, in inches.

-------------+---------------+-----------------+-----------------+-----------------
Times of | 2 | 3 | 4 | 6
Enlargement | | | |
-------------+-------+-------+--------+--------+--------+--------+--------+--------
Focus of | To | To | To | To | To | To | To | To
Lens | Easel | Lens | Easel | Lens | Easel | Lens | Easel | Lens
-------------+-------+-------+--------+--------+--------+--------+--------+--------
6 inches | 27 | 9 | 32 | 8 | 37-1/2 | 7-1/2 | 49 | 7
8 " | 36 | 12 | 42-2/3 | 10-2/3 | 50 | 10 | 65-1/3 | 9-1/3
10 " | 45 | 15 | 53-1/3 | 13-1/3 | 62-1/2 | 12-1/2 | 81-2/3 | 11-2/3
12 " | 54 | 18 | 64 | 16 | 75 | 15 | 98 | 14
-------------+-------+-------+--------+--------+--------+--------+--------+--------

A table for enlargements of from one to twenty-five times, with lenses
varying in focal length from three to nine inches is here given.

ENLARGEMENTS

_From the British Journal of Photography Almanac._

+----------+-----------------------------------------------------------------------+
| Focus of | |
| Lens | Times of Enlargement and Reduction |
+----------+------+--------+--------+--------+--------+---------+--------+---------+
| Inches | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| | inch | inches | inches | inches | inches | inches | inches | inches |
+----------+------+--------+--------+--------+--------+---------+--------+---------+
| 3 | 6 | 9 | 12 | 15 | 18 | 21 | 24 | 27 |
| | 6 | 4-1/2 | 4 | 3-3/4