When acquiring hemispherical canopy photographs in the field, the basic goal is to obtain high quality photographs.
Photograph quality is critical.
Poor quality photographs are difficult to analyze and can produce ambiguous results. Good quality photographs result when sufficient care is taken to position, level, and orient the camera correctly, when the exposure is correct, when the sky lighting is very even, and when there are no bright reflections. High contrast images with even sky lighting are best obtained on days with evenly overcast skies, or, if this is not possible, early in the morning or late in the afternoon. A high quality hemispherical lens should be used if available, though for many purposes satisfactory results can be obtained using an inexpensive hemispherical lens that fits in front of the standard lens of a 35mm camera. High quality hemispherical lenses and rugged cameras are manufactured by many companies, including Canon, Minolta, and Nikon.