This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Under-Exposure. If a negative has not been given full exposure, and is not treated for under-exposure in the developing, it will lack detail in the shadows, and the result is extreme contrast. (See Illustration No. 37.)
324. Illustration No. 38 shows a correctly developed, under-exposed negative. While all the detail possible with the exposure given has been retained, yet we have not as much detail as in the correctly exposed negative, as is shown in Ill. No. 34. The development has been carried until the highest points of light are almost as dense as the high-lights in the correctly developed normal exposure.
325. An under-exposed negative should not be carried quite as far in the developer as a correctly exposed one, for if carried too far, or even as far as the normal negative, the result will simply be still greater contrast and danger of chemical fog veiling the shadows. Proper manipulation will produce a print as shown in Ill. No. 37. By comparing this print with Ill. No. 33 you will see that there is, however, considerable difference, for Ill. No. 37 is very weak as compared with Ill. No. 33, which latter is strong and brilliant, and has everything to be desired in a good print. But unless the under-exposed plate had been nursed in development the results would have been harsh and worthless.