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Differences between the standard and sample

It is important that the reference material be of a similar reflectivity and have similar

properties to the sample. Otherwise large errors can be introduced, if for example a

poorly reflecting material is measured relative to a highly reflective PTFE reference

plate. The table below lists the appropriate reference materials that are recommended for

use.

Surface type Reflectivity Reference

Matt High PTFE reference plate

Matt Low

Labsphere diffuse

reflectance standards

Glossy High PTFE reference plate

Glossy Low NIST SRM 2021

The Troubleshooting section contains information on the available reference surfaces.

Figure 7: Highly diffuse samples are measured against a flat PTFE reference plate

Inaccuracy in the standard

If the standard material used to calculate a value is not accurate, this will hamper the

determination of the reflectance of the sample. Great care must be taken to keep reference

materials clean and unscratched.

For a detailed discussion on the factors affecting the measurement of diffuse reflectance

and transmission with integrating spheres, refer to reference (2).

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