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VIII. A Method and Instrument for the Measurement of the 

 Visibility of Objects. By Loyd A. Jones *. 



Introduction. 



DURING the summer of 1917 when the ravages of the 

 submarine began to oe a serious menance to marine 

 shipping, various schemes of painting were devised, designed 

 to protect the surface craft from attack by the submarine. 

 The object of these earlier systems of painting was to render 

 the vessel thus painted as invisible as possible and thus to 

 elude observation by the submarine operator. Extravagant 

 and conflicting claims were made as to the efficiency of the 

 various methods and no satisfactory means of deciding upon 

 their relative merits appeared to exist. It was at this time 

 that Mr. Lindon W. Bates, Chairman of the Engineering 

 Committee of the Submarine Defence Association, requested 

 us to take up the problem of finding some precise means of 

 measuring the visibility of ships painted according to various 

 of these low visibility schemes and further to devise, if pos- 

 sible, a system of painting giving the lowest possible 

 visibility. Some means of precise measurement was highly 

 desirable in order that the claims of the various systems 

 might be correctly evaluated by a method not involving a 

 personal judgment. 



When the work on this subject was taken up a survey of 

 the field showed that at that time no method for the numerical 

 specification of visibility, or instrument for its quantitative 

 measurement, was available. The first step, therefore, was 

 the working out, from the theoretical standpoint, of the 

 fundamental laws upon which the quantitative evaluation of 

 visibility could be based. Following this an instrument^ 

 operating upon the proper principle as indicated by the 

 theoretical equations and suitable either for the measure- 

 ment of visibility values of small models under known 

 conditions of illumination and background or of actual boats 

 at sea, was designed and built. 



The method and instrument proved to be entirely satis- 

 factory and some very interesting practical results were 

 obtained in the examination of various so-called low visi- 

 bility systems of painting. However, it is not the intention 

 of this paper to deal with practical results but rather to con- 

 fine ourselves to a treatment of those phases of the problem 



* Communication No. 79 from the Research Laboratory of the Eastman 

 Kodak Company. Communicated by the Director. 



