Brightness analysis

What is it?

Brightness is the visual sensation that one surface gives us when it reflects the incident light. However, there are two ways in which the light is reflected. One type of reflection is diffusive and there is no way of correlating the intensity of the reflected light with that of the incident light.
The second mode of reflection is specular, which means that all the incoming light rays are reflected in one direction, leading to a light intensity that can be related to the incoming intensity.
The figure below shows the difference between specular (a) and diffusive (b) reflection.



This technique allows the brightness to be determined through the relation of light intensity reflected from the incidence point to the internal reflection board of the apparatus. The final result is expressed as a percentage of reflected light over the total received by the surface, while showing the angle of its measurement.

What is it used for?

This technique allows for the measurement of brightness on different surfaces. It is capable of measuring curved surfaces such as molded plastic pieces, bottles, telephones or furniture with both matte and high gloss finishing. This parameter is very important because it can be applied to a wide range of materials such as tissues, wood, leather and glass, etc.

Equipment and working conditions

The brightness is measured using Novo Curve equipment from Rhotopoint.
This parameter is calculated through the integration of the amount of reflected light in the specular direction in a test area on the surface of the sample. In this case, the area is 2×2mm. This equipment has an optical block of aluminum that ensures angular integrity of ±0.1ᵒ in keeping with standards such as ISO 2813. It is possible to measure brightness scaling up to 60ᵒ of incidence and the readings are obtained in brightness units as defined in the ASTM D523 standard.

Example of use

Evaluating the brightness of metal coatings (silver).