Illumination:

Prerequisite for appearance evaluation is direct illumination. Diffuse illumination causes diffuse reflection and decreases the gloss impression.

Observer:

Eyesight and mood have a decisive role in the visual judgement. Also, it is important what our eye is focused on.

Appearance Perception

Uniform appearance is an important quality criterion for many products. Gloss effects are based on the interaction of light with the physical properties of the sample surface. The other influencing component is the physiological evaluation scale.
The human eye is still the best tool to evaluate gloss differences. However, control by visual analysis is insufficient, because


• evaluation conditions are not clearly defined, and
• people see and judge differently


In addition, subjective perception of appearance is dependent on personal experience: what is glossy for a paper manufacturer might be dull for an automotive maker.
The following criteria are involved in visual evaluation:

Surface Condition:

• Material (eg. coating, plastic, metal)
• Structure (eg. smooth, rough, wavy)