54 CIRCULAR 3 3 3, U.S. DEPARTMENT OE AGRICULTURE 



bility of a repeat picture should be borne in mind in photographing 

 every scene; features that are likely to change in a significant 

 way should be sought, and views that are likely to be hidden later 

 by brush or reproduction should be avoided. 



In photographing seedling stands, the usual tendency is to set up 

 the camera so that the picture is longer horizontally than vertically. 

 In later years this set-up becomes undesirable, because the narrow 

 vertical section is inadequate to register height growth. If a seed- 

 ling stand has features that can be made to stand out only by hori- 

 zontal photographs, then two photographs are necessary, the hori- 

 zontal to show the stand as it appears at the moment and the verti- 

 cal one to be used in connection with later repeat work. 



Individual seedlings should be photographed against a contrast- 

 ing background, as in plate 2, B. 



In the early history of a plot many more photographs should be 

 taken than are needed immediately. As time passes the value of 

 photographs will change, and some of them may retain no signifi- 

 cance except as records of original conditions. For example, some 

 repeat photographs may not show clearly the changes that have 

 taken place on the plot, and in others the view of significant features 

 may be completely obstructed by brush. An especially generous num- 

 ber of pictures should be taken on a plot that is to be treated, so 

 that those having little record value after the treatment may be 

 discarded. 



In order that repeat pictures may be made from the identical 

 points from which the original ones were made, the " camera points " 

 for all pictures to be repeated should be permanently marked 

 (p. IT), given distinctive numbers, and referenced to permanent 

 plot-boundary stations or numbered trees. It is recommended that 

 at least 4 such camera points be established on each plot up to 

 three-fourths of an acre in size, 6 on each plot of from three- 

 fourths to 1 acre, 8 or more on each plot larger than an acre, and 

 at least 1 for each 3 chains of line transect. Plot and subplot corners 

 often make excellent camera points. 



When possible, photographs should be developed while the party 

 is still in the field. This practice permits " retakes " of any photo- 

 graphs that are not clear or sharp. When such prompt developing 

 is impossible, it is often advantageous to take more than one photo- 

 graph from a given camera point to allow for possible failures. 

 The duplicate photographs should be made with different timing 

 or different aperture from the first exposure, as a check on the 

 first effort. They can be distinguished from it and from each other 

 by changing the position of some identifying object in the view 

 between exposures and making a note of the change. 



A camera to be used for sample -plot work should preferably take 

 pictures at least 5 by 7 inches in size and have a ground glass on 

 which the view can be focused. 28 Only in rare instances should a 



28 Many arguments have been advanced in favor of small cameras, but these break 

 down when the photographs are examined. Almost invariably repeat photographs fail 

 to coincide and the number of successful, worth-while prints is low. The use of 

 small cameras leads to hasty and ill-considered work and to the making of numerous 

 snap-shots rather than careful photographs. Although low expense is an argument often 

 advanced, the average cost of a successful photograph is often as great for a small 

 camera as for a larger one. Small cameras are decidedly easier to carry ; but in relation 

 to permanent plots, which usually are readily accessible, the difference in ease of 

 transportation is not important. 



