BROMIDE PAPER 203 
of either the correct exposure or the correct time of develop- 
ment is a complete guide to both exposure and development, 
since they are dependent variables in the sense that the pro- 
duct of one with the other is a constant quantity. The third 
rule is: the maximum development allowable is that which 
just stops short of fog or stain or both. Each developer has 
its own factor, which in the sense of the above rules varies 
within certain limits, these for the Kodak amidol being from 
10 to 30. As a mean 12 is convenient, and it is advisable to 
adopt this and make trial exposure strips. He lays down the 
axiom that the correct exposure for a bromide print is that 
which, when developed with any developer to an appropriate 
Watkin’s factor, yields a print of the desired depth. This 
is the only definition in existence, which has any value in 
practical work. 
