It is difficult to describe a colore or even a color difference on the telephone without color measurements. We can describe the direction where we have to go like:  „The sample has to be darker, a little bit stronger and a bit more yellow“, but how much is „a little bit“?   

Different kinds of instruments are available on the market. They vary in the way how to illuminate the sample, how to collect the reflected light and how to process the data.

The measurement geometry (d:8°, 45°:0° or multi angle) is given by the geometrical setup of the instrument. There is no instrument on the market which can be switched from one geometry to another one, it is either d:8° or 45°:0° or a multi angle instrument.

Which geometry is now the right one?

There is no right or wrong. Different applications need different measurement geometries.  Depending on what the measurement should be used for, the right type of instrument should be selected. The following paragraphs try to explain this.