Radiometry and Photometry

Radiometry is the science of measuring electromagnetic radiation. Photometry instead, uses light as perceived by the human eye and its sensitivity to different wavelengths. 

Radiometry:

Radiometry is the science of measuring electromagnetic radiation. It is used to measure the power, intensity, and spectral distribution of radiation. Radiometry is important in a variety of fields, including astronomy, remote sensing, automotive industry and medical imaging.

There are two main types of radiometric measurements: absolute and relative. Absolute measurements measure the total power of radiation emitted by a source. Relative measurements measure the power of radiation relative to a reference source.

Radiometric measurements are made using a variety of instruments, including radiometers, spectroradiometers, and pyrometers. Radiometers measure the total power of radiation, while spectroradiometers measure the spectral distribution of radiation. Pyrometers measure the temperature of objects by measuring the amount of radiation they emit.

Radiometry is a powerful tool for measuring electromagnetic radiation. It is used in a variety of fields to study the properties of materials, measure the temperature of objects, and map the surface of the Earth.

Photometry:

Photometry is the science of measuring light as perceived by the human eye. It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power.

Photometry is based on the human eye's sensitivity to different wavelengths of light. The eye's sensitivity is represented by a function called the photopic response. The photopic response is a curve that shows how the eye's sensitivity to light changes as a function of wavelength.

Photometric measurements are made using a variety of instruments, including photometers, spectrophotometers, and colorimeters. Photometers measure the brightness of a light source, while spectrophotometers measure the spectral distribution of light. Colorimeters measure the color of a light source.

Photometry is used in a variety of fields, including astronomy, lighting design or colorimetry.