Resolution

The ability of an instrument to differentiate between two energies (or wavelengths, or frequencies, or masses) that are relatively close to one another is referred to as its resolution. In most cases, a higher resolution for an instrument that utilizes mechanical slits will result in decreased intensity.

Spectral resolution

A spectrograph's or, more generally speaking, a frequency spectrum's spectral resolution can be thought of as a measurement of how well it can distinguish between different elements present in the electromagnetic spectrum. It is commonly denoted by

where {\displaystyle \Delta \lambda }\Delta \lambda is the smallest difference in wavelengths that can be distinguished at a wavelength of {\displaystyle \lambda }\lambda .