Why is it not enough to measure only gloss?

For many years a standard gloss meter has been specified and used as a Q.A. tool for quantifying and validating surface appearance quality. It is based on a long established measurement principle, this compares the amount of light transmitted onto a surface with the amount reflected from it at a fixed measurement angle.  This produces a value of gloss unique to that surface. This gloss value, however, can often be misleading as it does not define other surface appearance effects that can be seen visually.

The ten panels above demonstrate this visual difference.

When measured using a standard gloss meter, each of the panels produces the same gloss value however to the eye they appear different.

This visual versus measured discrepancy is due to the texture being present on the surface caused by large (orange peel) and microscopic structures (haze).

Due to the limitations in measurement technology a gloss meter is, therefore, unable to detect these structures as it can only determine gloss values hence why visually the surfaces appear substandard.