How do you measure relative diffuse reflectance?

The figure here shows a diagram of the measurement.

Reverse the roles of sample and reference beams in measurement parameter settings.

In Shimadzu software, this means setting the S/R switching function to reverse.

Attach a white reference plate at position (2) of the integrating sphere. Perform baseline correction. The sample beam shines on the white reference plate.

Remove the white reference plate from position (2) and attach the measurement sample in its place. For Shimadzu integrating spheres, the beam shines on the sample at an incident angle of 8 degrees.