The invention relates to a spectrophotometer with a modular 45/0 head. In one embodiment, the invention is a spectrophotometer with a modular 45/0 head. One embodiment of an apparatus for measuring a reflectance of a sample includes a plurality of light emitting diodes for emitting light, a reflective housing positioned above the plurality of light emitting diodes, where the reflective housing is a dome having a plurality of apertures formed around its perimeter, a sample channel for capturing a first portion of the light, where the first portion of the light interacts with the sample, and a reference channel for capturing a second portion of the light, where the second portion of the light is independent of the sample.