Integrating spheres collect and spatially integrate radant flux. The flux can be measured directly or after it has interacted with a material sample. The sphere as part of a radiometer or photometer can directly measure the flux originating from lamps and lasers or the flux density produced from hemispherical illumination. Perhaps the largest application for integrating spheres is in the measurement of the total reflectance or transmittance from diffuse or scattering materials.