Spectrophotometry is concerned with visible light, near-ultraviolet light, and near-infrared light. A spectrophotometer is a device used to measure light intensity as a function of color, or, the wavelength of light. Those who make custom inks must take advantage of this complex technology because doing so provides the particular data of colorimetry that provides the numerical elements for matching to the specifications of ink being copied. In addition, dedicated ink manufacturers concerned with a color's potential fluorescence, an element that isn't easily detected and which can cause matching difficulties, must use a bi-spectral fluorescent spectrophotometer.

Fluorescence in ink is used for security in the printing of money. Other types of ink can help guard against counterfeiting, and these include metallic, magnetic, and optically variable inks, in addition to iridescent coating. Ink manufacturers are familiar with these varieties, as they must know what kind they are seeking to copy or to avoid when they create custom inks. Ink is able to incorporate within itself materials that fluoresce. When viewed under ultra violet light the fluorescent graphic elements are visible. Metallic types are used in larger areas of solid color on money, and they produce a sheen. Magnetic inking is useful in money because, of course, its unique properties can be caught by a magnetic detector. Often these inks are used on the serial numbers of a bank note. OVI, or optically variable inks, gain their optical properties when the miniscule flakes of special film shift color when the viewing angle varies. Because these are costly, they are used mostly for smaller areas on currency. Finally, iridescence is applied during the printing process before any pigments, and the pearlization can be seen as a band or a solid or pattern.