PHOTOGRAPHY Ig!i 
with the Stanley plate as with the others, and consequently now uses it 
exclusively, since it is cheaper. The one important point is to make a final 
choice only after personal experience, and then to always use plates of the 
same brand, and preferably of the same rate of speed. 
238. The use of the camera. To the ecologist, objects to be photo- 
graphed fall into two categories, viz., those that move, and those that do 
not move. For practical purposes, areas sufficiently distant to render the 
movement imperceptible belong to the latter, as well as those, such as rock 
lichens, many fungi, etc., which can not be stirred by ordinary winds. The 
treatment accorded the two is essentially different. A fundamental rule of 
ecological photography is that detail must receive the first emphasis. The 
ecological view should be a picture as well as a map, however, but when one 
must be sacrificed, artistic effect must yield to clearness, and accuracy, i. e., 
technically speaking, contrast must give way to detail. Leaving apart the 
necessity of securing a sharp focus, which holds for all work, detail or defi- 
nition depends directly upon the aperture of the diaphragm. Detail is in- 
creased by decreasing the size of the aperture. This in turn increases the 
length of time necessary for a proper exposure, and consequently the danger 
that the plant will be moved in the midst of the exposure. When the move- 
ment is negligible, the invariable rule should be to reduce the aperture to its 
smallest size, and to expose for a corresponding time. In all cases where 
the plants are close enough to show even a slight blurring on account of the 
action of the wind, the time of exposure must be reduced, in the hope that 
a short period of quiet will suffice for it. This reduction in time must be 
compensated by increasing the aperture of the diaphragm, and hence the 
amount of light which strikes the plate. The proper balance between the 
two is a matter of considerable nicety. It depends much upon the vagaries 
of the wind, and can readily be determined only after considerable ex- 
perience. Although regions naturally differ somewhat in the nature of their 
winds, much experience in prairie and mountain regions warrants the 
primary rule that views of vegetation and plants subject to movement are 
not to be attempted on windy or cloudy days when it can possibly be avoided. 
Even on reconnaissance, a poor picture is no better than none at all, while 
in resident work a time will come sooner or later which will permit the 
making of a view satisfactory in all respects. There may be occasional in- 
stances when one is rewarded for keeping the camera trained on a particular 
spot for hours, and for wasting several plates in the hope that still mo- 
ments will prove to be of the requisite duration. As a regular procedure, 
however, this has nothing to commend it. 
Various methods have been tried to reduce or eliminate the trouble caused 
by the wind. Canvas screens have been used for this purpose with some 
