Lux is a measurement of luminance which accounts for a quantity of light as applied over a surface, and most color meters can display lux. Thus, if you use a color meter (or any other meter giving lux but not EV values such as conventional incident exposure meters) for your work and would like to also use it to provide exposure readings, the combination of the lux reading from your meter and this Gossen Calculator can give you a range of shutter speed and aperture values which will yield a proper exposure.