TECHNIQUE OF DEVELOPMENT 357 



Good results have been reported with this system, but it has not been used com- 

 mercially to the extent of the other systems mentioned. 



Other Agitation Systems. For Laboratory Use. — In search for uniform reproduc- 

 ible development for test purposes a few other specialized devices have been devel- 

 oped. One of these for which the best results are claimed utilizes a relatively slow 

 circulation for temperature control and a violent turbulence at the emulsion surface 

 produced by blades moving close to, but not in contact with the emulsion surface. 

 This mechanism is primarily designed for film, and arrangements are provided to hold 

 the test strips rigidly and accurately to provide uniform clearance between the emul- 

 sion and the agitator blade. This blade is driven by a reciprocating mechanism, and 

 the entire assembly is mounted in a thermostatically controlled bath. The film 

 strips are vertical and the capacity is limited by practical rather than theoretical 

 considerations. 



The high degree of uniformity reported for an extended series of tests cannot be 

 entirely due to this machine but must also be due to precision control of procedures at 

 all other points in the test system. 



In some test equipments the object is not entirely the attainment of highest theo- 

 retical perfection but is the simulation of commercial procedures, which, while they 

 may be known to be lacking in some respects, may be the controlling objectives from a 

 business viewpoint. Laboratory equipment designed to closely approximate com- 

 mercial machine equipment (in which the chief agitation is due to film motion) has 

 been designed, built, and used successfully. To bring this to a laboratory scale of 

 size and yet not limit the linear speeds which can be used, the film is formed in a 

 loop and driven around and around at any desired linear speed; no excessive bulks 

 of solution are required, and the equipment can duplicate reasonably well many 

 trade practices, yet be subject to the refinement of control needed for laboratory 

 work. 



Producing and Reproducing Results. — In a broad sense, there is no one standard 

 universally applicable by which to judge correct development. In an artistic sense 

 that development is right which gives the desired result regardless of custom, habits, 

 and normal criteria. In technical or scientific work there are usually rather narrow 

 limits within which results are accurate and satisfactory. In commercial operations 

 there are often photographic steps which must be controlled within narrow practical 

 tolerances to fit the photographic results to the needs of the other phases of the work. 

 The motion-picture industry is the greatest commercial user of photographic materials, 

 and great care must be exercised to maintain uniformity of development in order to 

 permit the full artistry of the director, the cameraman, the actors, and the actresses 

 to come through to the theater for the enjoyment of the public. 



The final criterion of the success of all photographic development is the suitability 

 of the resultant image for its intended purpose. The logical extension of this state- 

 ment leads to the conclusion that the same emulsion may need to be developed different 

 ways for different purposes. As a corollary, no development can be judged com- 

 pletely for its correctness without knowledge of the purpose which is to be served. 

 When stated explicitly, these appear truisms, but failure to consider them in their 

 logical relationships is rather common. The question "Is this developed correctly?" 

 has no answer unsupported by other circumstance and condition. However, we live 

 in a world such that few of us are pioneers, and, fortunately, it is not often necessary 

 to start into uncharted seas of "correct" and "incorrect" development. In the 

 early stages of any photographic experience criteria by which to judge correct develop- 

 ment for the purposes involved are learned by necessity, to greater or less degree. 

 This initial information is usually imparted along with some specific test or method by 

 which to judge future developments. 



