The focal length measures the strength of an optical system to converge (focus) or diverge light. It is related to the radius of curvature and inversely proportional to the optical power.
Coatings are used to alter the reflective properties of a surface. They can be used to increase transmission (AR Coatings), increase reflection (HR Coatings) or selectively transmit or reflect certain wavelengths.
Quantifies the range of angles over which an optical system can accept or emit light. In a single lens, it is proportional to the optics diameter and inversely proportional to the focal length.
The f/# is the ratio of the focal length, (f), of the lens to the effective aperture diameter. The larger the f-number, the smaller the aperture, and the lower the light throughput.
The clear aperture is the pupil of the system that preserves all specifications defined by the manufacturer. It is always smaller than the diameter of the optic.
The focal length measures the strength of an optical system to converge (focus) or diverge light. It is related to the radius of curvature and inversely proportional to the optical power.