1. Light source

When comparing color, it is advisable to choose a soft light source from the north. Colorists should turn their backs to north. The best time to color is: three hours after sunrise and three hours before sunset.

2. Objects

Objects should provide as accurate color information as possible. Therefore, the surface of the object should be clean to avoid paint aging, discoloration and pollution. The colorimetric background should be based on light tones, avoiding too bright and too dark.

3. Observer

No color weakness, color blindness.

Colorimetric method:

a) Visual inspection method: directly use the paint mixing ruler for color comparison. Fast, but less accurate.

b) Smearing method: Smear the color paint on the sample or sheet for color comparison. High accuracy for solid color paint, but longer drying time.

c) Spraying method: color comparison is carried out by spraying a plate. The highest accuracy, but the operation is more complicated.