Colorimeters

Geometry

The geometries of colorimeters refer to the different ways in which a colorimeter can measure the color of a surface. These geometries affect how light falls on the sample and how it is measured. Each geometry is suitable for different types of applications, depending on the nature of the material being measured and the type of color information required. Below are the common geometries and their recommended applications:

0°/45° or 45°/0° (0°:45° or 45°:0°):

• Application: This is one of the most common geometries and is used to measure color in a way that closely matches human visual perception. It is often used for surfaces that are approximately flat and do not have texture or gloss, such as printed materials, paints, and plastics.
• Details: It illuminates the sample at an angle of 45 degrees and measures the reflected light at 0 degrees (perpendicular to the sample), or vice versa.

Diffuse/8° (d:8°) or 8°/Diffuse (8°:d):

• Application: This geometry is ideal for woven or uneven surfaces, such as fabrics, carpets, and nonwoven materials. It is also used for samples with surface gloss.
• Details: The sample is illuminated diffusely (from all angles), and the reflected light is measured at an angle of 8 degrees, or vice versa. This arrangement includes an integrated spherical illuminator to ensure diffuse illumination.

Aperture

The aperture size (or opening) in a colorimeter significantly affects color measurement, especially when dealing with samples of different sizes, textures, or patterns. The aperture is the part of the colorimeter that controls the size of the area that is illuminated and measured on the sample. The main effects of different aperture sizes are as follows:

Large Aperture Size:

• Effect on Measurement: A larger aperture covers a wider area of the sample. This is beneficial when it is necessary to evaluate color over a larger area, which is particularly important for heterogeneous or patterned samples, where small areas may not be representative of the overall sample.
• Suitable for: Ideal for samples with uneven color distribution, large patterns, or texture variations. This includes materials such as natural products (wood, stone), patterned fabrics, or samples with grain.

Small Aperture Size:

• Effect on Measurement: A smaller aperture allows more accurate, localized color measurements. This is critical when measuring small samples or specific points on a sample. It helps accurately characterize colors without interference from surrounding areas.
• Suitable for: Best for small samples, samples with small, detailed patterns, or when you need to measure a specific part of a heterogeneous material without averaging over a larger area. This may include measuring the color of small printed characters, spots on fruit, or specific components of a composite material.

Adjustable Aperture Size:

• Effect on Measurement: Some advanced colorimeters have adjustable apertures, allowing the user to change the opening size depending on the sample requirements. This flexibility is beneficial for various applications.
• Suitable for: Ideal for laboratories or industries where a wide range of sample types and sizes are measured, requiring both broad-area and localized color measurements.