Results can be automatically output to data files for archiving and further analysis. Typically, each photograph can be analyzed in two to five minutes, including all steps of film positioning, digitization, selection of a threshold, calculation, and output of results. Access to intermediate calculations of the distribution of canopy openings as a function of zenith and azimuth angles allows users to design their own detailed analyses of canopy geometry. In addition, the image analysis system must include a video display monitor, video camera fitted with a macro lens, backlighting source, film holder, and copy stand. Appendix B gives further details concerning hardware.
Costs are approximate.
Until recently, interpretation of hemispherical photographs has required tedious manual analysis using sampling grids. Jupp et al. With hemispherical photography, any plant canopy can be studied, ranging from crop systems to natural forests, as long as it is feasible to take photographs from beneath the canopy. Hemispherical photographs can be taken above individual plants growing in the understory, to study relations between understory light, ecophysiology, and demography. Light maps can be constructed, by acquiring hemispherical photographs at series of horizontal and vertical positions, to examine spatial and temporal variability of light under plant canopies.