neighborhood of +0.05 centimeters, (2) tliough 

 within these limits, there is a slight difference 

 between the results obtained by two readers, 

 and (3) these results were obtained even though 

 the device was disassembled and assembled 

 prior to each test. 



Base 



To make the photographic device port- 

 able, the base must be made in three parts so 

 that it can be disassembled for easier trans- 

 porting . 



Sources of Error 



General Design Improvements 



There are many sources of error in the 

 present device and techniques. Some of these 

 sources of error are: (1) the grid lines, (2) the- 

 glare, (3) the calibrated knob, and (4) the steel 

 tape used. 



Grid lines. --The grid lines were scribed 

 by hand on the base and under the microscope 

 appear quite wavy. In addition, the lines are too 

 heavy. 



Glare. --The reflector used does not dis- 

 tribute the light evenly enough and "hot spots" in 

 some areas of the grid cause glare. Whenever 

 the point of measurement falls in one of these 

 "hot spots", the definition of the point is not 

 clear in the negative and misinterpretation of the 

 exact point of measurement can result. 



Calibrated knob. --The calibrated knob on 

 the stage of the microscope is undersized. That 

 is, there is room only for every other whole num- 

 ber to be marked. Accurate interpolation to 

 tenths of a number, consequently, is not possible. 



Steel tape. --Since the grid lines on the 

 base were wavy and inaccurate, a millimeter 

 steel tape was used to determine the exact meas- 

 urement between the grid lines. Recently, we 

 had this steel tape calibrated. Though we have 

 not had the opportunity to double -check this cal- 

 ibration, the results indicate that the tape is not 

 accurate . 



FUTURE WORK 



Strobe light . --The strobe light now in 

 use was .chosen because it was available im- 

 mediately. Consequently, a search of other 

 commercial models might turn up one that is 

 much smaller in size and weight. 



A reflector designed to distribute the 

 light more evenly may improve the resulting 

 pictures. 



Power pack. --No attempt has been made 

 to determine the size of the batteries needed, 

 and much smaller batteries undoubtedly could 

 be used. 



Cameras. --Two additional features that 

 would increase the efficiency of the cameras 

 would be (1) automatic sequence (self -winding 

 and (2) large film capacity. 



Another possibility is the use of a camera 

 incorporating a sterio -optical lens system. 

 This would reduce the total cost of the device 

 since one camera could be used instead of two. 



Film . -- A systematic check of the var- 

 ious types of commercially available films 

 should be made to determine one that is fast, 

 and thus not so sensitive to a wide range of 

 natural light, and yet fine grained to afford 

 great detail. Films should be tested in the 

 photographic measuring machine under various 

 conditions of natural light to determine the best 

 one to use considering the strobe light, fish be- 

 ing photographed, and other related factors. 



Many improvements can be made on the 

 photographic measuring machine. The following 

 are a few of the more obvious ones: Portability, 

 automatic features, and accuracy. 



Portability 



Automatice Features 



The replacement of manual operation with 

 automatic operation is one way in which errors 

 can be reduced and efficiency increased. Since 

 the reading of the film and the calculation of the 

 final measurements are the aspects of this 



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