Many, if not most, geologists, use photography in their field work but, as they have many other duties, they can not use the heavy equipment commonly used by professional photographers. This paper presents some of the basic principles of photography, the materials commonly used in the field, apparatus adapted to the needs of geologists, and some hints on proper practice in taking photographs. Particular attention is given to the use of filters, which are essential to successful work on both distant landscapes and the details of rock exposures. The blurring effect of haze and dust may be minimized by using only the color with the longest wave length to which the film is sensitive. The narrower the range in colors used, the greater the sharpness of the picture. To secure de ails in pictures of rocks a filter of the same color should be used. The mottoes of the field photographer must be "Always be careful" and "Practice makes perfect."