MOTION-PICTURE PHOTOGRAPHY 699 



An obvious advantage of the test system is that it affords a degree of protection 

 to the studio and the cameraman against mistakes in exposure. It is certainly to be 

 preferred in those cases where the cameraman has been "fighting light" outdoors late 

 in the afternoon — perhaps shooting under protest — to get the requisite number of 

 scenes for the day. It also permits over- and underdevelopment of negative as a 

 means of securing uniformity in printing, but at the expense of quality — a dubious 

 advantage. The disadvantages are the extra handling to which the negative is sub- 

 jected in rewinding to detach and segregate the tests; the possibility of misjudgment 

 by the timer; the possibility of conflict between the cameraman and the laboratory 

 over questions of timing; and the tendency of some cameramen to rely on the labora- 

 tory to save them from the consequences of their under- and overtimings, to the 

 ultimate deterioration of their work. 



Whatever method is used, sensitometric control is required to keep the solutions 

 constant, since variations in the "soup," whether erratic or gradual, are as little 

 desired in laboratories employing the test system as in those which adhere to the con- 

 stant-time system. When a new developer is mixed, it is necessary to determine the 

 footage speed and development time which, for normally exposed negative, will yield the 

 desired gamma. This involves varying the speed in the neighborhood of the normal 

 speed, developing a number of sensitometric strips on the same photosensitive material 

 as the negative which is to be developed, and from the resulting data constructing a 

 short time-gamma curve from which the time and footage speed corresponding to the 

 desired gamma may be read off. If the constant-time system is in use, all the negative 

 then goes through at this speed, but every hour or half-hour the constancy of the 

 conditions must be rechecked by the same procedure, a single strip being usually 

 sufficient. Unless the original test is duplicated for both density and gamma, adjust- 

 ments in the developing solution are required. Aside from variations in the agitation 

 and temperature, which are unlikely in modern laboratories, an important variable is 

 the chemical change in the developer as it acts on large quantities of film. It is neces- 

 sary to replenish or "boost" it periodically, and the proper amount to be added is 

 indicated by the tests, although usually it is quite accurately known from experience. 

 New developer may be added manually or, preferably, by the drip method of constant 

 admixture. 



By the control methods described, the average negative gamma varies among 

 motion-picture laboratories between 0.60 and 0.75, with an average of 0.67. The 

 gamma is normally controlled to ±0.03. 



Another application of sensitometric control which requires mention is in connec- 

 tion with new emulsion numbers of raw stock, which must be correlated with the 

 outgoing emulsion number. This is particularly important in connection with positive 

 stock in order to ensure uniformity in release prints. The procedure is to select a 

 number of rolls of the old and the new coatings, and to make from two to five sensito- 

 metric strips from each. Lengths of both emulsions are then printed on a master 

 printer, maintained with special care mechanically, electrically, and optically as a 

 reference machine. A selected picture negative is used as a standard for this printing. 

 The prints on all the samples are made at the printer step which was correct for the old 

 emulsion, and the sensitometric strips and prints are developed together under the 

 preexisting conditions. The step densities are then read on the densitometer and 

 plotted, whereupon any required change in printer point to compensate for the change 

 from the old to the new emulsion becomes apparent. 



Prints for studio use are a relatively small part of the work of the laboratory's 

 printing department, in comparison with release printing, which usually requires 

 several hundred copies of each feature in the form of composite prints. Modern 

 printers operate at speeds of about 180 ft. per minute. A typical picture printer is 



