TABLES 602-609.-PHOTOGRAPHY *
TABLE BOP.-SENSITOMETRI~C CONSTANTS OF TYPE PLATES AND FILMS,
is a measure of the degree of blackening of an exposed film or
plate after development. Density is defined in general terms as the logarithm of the ratio
of the radiant flux, Po, incident on the sample to the radiant flux, Pr, transmitted by the
Log exposure (mcs)
characteristic curve. Ordinates are diffuse transmission density (D) :
abscissae, logs of exposure (log E). A-C = toe, C-E = straight line, E-F = shoulder,
B = sped point, B-D = Alog E = 1.50. Tan a = y, Tan b = p, Tan a = 0.38.
D =log (g)
Exposure (E).--E = It (expressed in meter-candle seconds). I = illumination (meter-
candles, mc) incident on the photographic material during exposure, t = exposure time in
is defined as the tangent of the angle alpha (a) (fig. 27) which
the straight-line part of the characteristic curve makes with the log-exposure axis.
Gamma infinity (ym ) . - - y ~
is defined as the limiting value to which gamma a p
proaches as development time is increased.
Time of development for the half gamma infinity (tY = -yJ2).-A
practical specification of development rate of significance in comparing developers.
Time of development for gamma of unity (tY = l.O).-A convenient practical speci-
fication of development rate of significance in comparing photographic materials. Compari-
sons must be confined to materials in the same developer.
Inertia (i).-i =the value of exposure where the straight-line portion of the character-
istic curve (fig. 27) extended cuts the log E axis.
Speed (S,).--S,=I/E, where E is the exposure corresponding to point B on the
D-log E curve in figure 27. This point is located in the following manner : A log exposure
range of 1.50, represented in the figure by the distance along the log exposure axis between
B and D, is selected in a region where the slope of