The quantitative relationship between the colors of different color cards and their measured optical density values.

**Optical Density (OD)** is defined as a characterization of a material's light-blocking ability. Optical density is a dimensionless logarithmic value. The concept of optical density was originally used in the field of photographic film and photographic paper (relationship between exposure and optical density). It has now been widely applied in the optical analysis and testing of materials such as photographic film, printing and packaging, photoresist inks, and reflective films.

**Measurement Principle**

Optical density is the logarithm of the ratio of incident light to transmitted light, or the logarithm of the reciprocal of light transmittance. The calculation formula is:

OD = lg (incident light / transmitted light) or OD = lg (1 / transmittance)

**Features**

- Wide range: OD measurement up to 6.5D

- Long-life LED light source

- Excellent data compatibility with other brands of transmission densitometers

- Wide sample size applicability: can measure the central part of A4-sized samples

- Data export and PC storage via USB

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