How to measure light and color?

How to measure light and color?

Here are three articles based on the provided information and additional details from relevant sources:

Introduction to Light Properties

Light is a form of electromagnetic radiation that our eyes perceive as different colors based on its wavelength. The visible spectrum ranges from approximately 400 nm (violet) to 800 nm (red), though most color calculations use the range between 380 nm and 780 nm. Understanding light properties is crucial for optical measurement techniques.

Thorough knowledge of the physical nature of light and light perception provides the foundation for a comprehensive understanding of optical measurement techniques. Yet from a practical point of view, there is little necessity to fully understand formation and propagation of light as an electromagnetic wave as long as the reader accepts wavelength as the most important parameter describing the quality of light.

The human eye perceives light with different wavelengths as different colors (s. Fig. 1) as long as the wavelengths are between 400 nm and 800 nm (1 nm = 1 nanometer = 10^-9 m), exactly 360 nm to 830 nm is the V(λ) and 380 nm to 780 nm for most color calculations.

In the electromagnetic spectrum optical range, the wavelength is sometimes also given in Ångstrøm (Å = 10^-10 m). Outside this range, our eye is insensitive to electromagnetic radiation and we therefore cannot perceive ultraviolet (UV, below 400 nm) and infrared (IR, above 80  nm) radiation.

Methods of Light Measurement

Light can be measured using spectral measuring devices or integral measuring devices. Spectral devices analyze specific wavelengths, while integral devices measure overall light intensity1.

Radiometry involves measuring the absolute properties of electromagnetic radiation across all or part of the spectrum, including UV to IR ranges.

These measurements are essential for applications like solar cell efficiency calculations, where incident optical power is compared with generated electrical power.

Photometry focuses on how humans perceive light in terms of brightness and color appearance. It uses a luminosity function (V(λ)) that accounts for human eye sensitivity to different wavelengths.

Photometry is vital for lighting design and ensuring appropriate brightness levels in various environments.

Color measurement involves analyzing how colors appear under different lighting conditions. This includes understanding color rendering index (CRI), which measures how well artificial light sources render object colors compared to natural daylight. Techniques like spectrophotometry help quantify these effects by analyzing spectral reflectance curves from objects under various illuminants.