The two most common spectrophotometers are the 0:45 and the sphere (aka diffuse/8°). We get a lot of questions about which is the best choice. Here’s the difference in how these two devices measure color, and guidelines for when to use each. 0:45 In a “fixed geometry” or “single angle” device, the first number is the starting point of the light, and the second number is where the light ends up after the reflection off the surface of the sample. In a 0:45 ...