Photosynthesis is an orchestration of multiple biochemical and biophysical processes that convert light energy into chemical energy (i.e., the light reactions) and subsequently assimilate carbon dioxide (CO₂) from the atmosphere into plant metabolites (i.e., the Calvin reactions). Both the light and Calvin reactions have been explored experimentally for decades with increasing precision and resolution as technology has developed. While measurements of both types of reactions are informative, the combination of the two can provide additional information about plant resource allocation, utilization efficiency and overall health.

Typical gas exchange measurements are used to quantify CO₂ and water fluxes across a leaf surface. The yield of chlorophyll fluorescence can be experimentally manipulated to provide information about how absorbed light energy is partitioned between photochemical, (e.g. electron transport), and non-photochemical (photoprotective) processes. These fluxes and yields of fluorescence can be measured under ambient environmental conditions (survey) or in response to changes in various environmental factors (response curves). Simultaneous chlorophyll fluorescence and gas exchange measurements on the same leaf area can be used to assess quantum (of light) efficiency of electron transport (φ_PSII) versus quantum efficiency of carbon fixation in the Calvin reactions (φ_CO2). From theory, there is a theoretical minimum