(2) Gamma is a numerical measure of the degree of development (for a given material).

(3) Technically, gamma is the slope of the straight line portion of the characteristic curve.

(4) Mathematically, gamma may be defined as follows:

(a) The ratio of the height gained (difference in any two densities on the straight line part of the

curve) to the horizontal difference (difference between the log E's which produced the two densities).

(b) The tangent of the angle formed by the intersection of an extension of the straight line

portion of the curve and the horizontal axis.

c. Gamma determination, once the curve has been plotted, can be accomplished by several

methods. Four methods are presented here:

(1) Basic method. This method, shown in figure _____, involves the ratio between densities

and the exposures which produced them. Any two points on the straight line are chosen. (More

reliability tends to result if the points are widely separated.) Gamma is the result of dividing the change,

or difference in density, by the difference in log E between the two points. The formula is

where

∆ (Delta) = Greek symbol for change or difference.

(2) Graphic method. From the inertia point (the point of intersection of the straight line

extended to the log E axis), move to the right a distance of 1.00 on the Log E axis. Gamma is the

density reading at this point.