The difference between SCI and SCE

February 23, 2024

SCI refers to the inclusion of specular reflected light mode, generally used for those who study the properties of the color itself without concern for the color attached to the surface gloss of the sample manufacturers, such as paint coating factories. SCE refers to the method that does not contain specular reflected light, which is generally suitable for those samples that are directly observed and require measurement results to be very close to the visual view, such as home appliance housings.

In the SCE measurement mode, specular reflected light is excluded and only diffuse light is measured. The value thus measured is comparable to the color of the object as it appears to the observer. When SCI mode is used, specular reflected light is included in the measurement along with diffuse light. The value measured in this way is the overall objective color of the object, and has nothing to do with the surface conditions of the object. These criteria must be taken into account when we choose an instrument. Some instruments can also measure values in both SCE and SCI modes.

Even if the object is made of the same material, the color will look different due to the difference in surface gloss. For example, when the surface of a smooth, bright blue sample is rubbed with sandpaper, why does the blue appear a little dimmer?

When the elastic ball is thrown at the wall and bounces back, the Angle is the same. In the same way, because the light source produces light that is reflected back from the same Angle in different directions, we call it mirror reflected light, because the light is like being reflected back by the mirror. Light that is not reflected by specular reflection but scattered in all directions is called diffuse light. The sum of specular and diffuse light is what we call reflected light.

On smooth, bright surfaces, specular light is stronger and diffuse light is weaker. On rough surfaces with low gloss, the opposite is true. When we look at a blue plastic object with a smooth surface at a specular reflection Angle, the object appears less blue because the specular reflection from the light source is added to the color of the object. Generally speaking, people ignore the reflection of specular light when looking at the color of objects. Therefore, when measuring such samples, in order to make the data look like the object, it is necessary to exclude specular reflected light and measure only diffuse light. The color of an object is different because of the amount of light reflected by the mirror we observe.

We already know that because people only look at diffuse light, when the surface conditions of the object change, the color will appear different. However, since the material of the object itself is the same, the color of the object should not change. How can we get the color of the material itself?

The content of specular reflected light and diffuse light is determined according to the surface of the object. But under certain conditions of material and color, the total amount of the two kinds of light is always the same. Thus, when the smooth blue plastic sample is roughened, the specular reflected light content decreases and the diffuse light content increases. This is why we need to measure the total reflected light (the sum of specular and diffuse light).