A densitometer is a device that measures the degree of darkness (the optical density) of a photographic or semitransparent material or of a reflecting surface.[1] The densitometer is basically a light source aimed at a photoelectric cell.[2] It determines the density of a sample placed between the light source and the photoelectric cell from differences in the readings.[3] Modern densitometers have the same components, but also have electronic integrated circuitry for better reading.[4]

Not to be confused with hydrometer which measures mass density of liquids.


  • Transmission densitometers that measure transparent materials
  • A transmission densitometer used to measure transparent surface measures color transparencies film &transperent substrate are some example of common transparent surface measures..
  • Reflection densitometers that measure light reflected from a surface.

Photography applications

Some modern types of German manufacture are capable of both types of measurements selectable by a switch. They are used in film photography to measure densities of negatives with the switch in the "T" (Transmission) position and the saturation of a resulting print in the "R" position. Such measurements enable the photographer to choose the right photo paper and the correct exposure, obviating experiments with test strips. Once the papers and darkroom have been calibrated, the first print from a previously measured negative is a success at once.


  • Densitometers are used for measuring color saturation by print professionals
  • Calibration of printing equipment
  • It serves as one of the Molecular tools for gene study, to quantify the radioactivity of a compound such as radiolabeled DNA.
  • They are also used for making adjustments so that outputs are consistent with the colors desired in the finished products.
  • They are used in industrial radiography to ensure x-ray films are within code-required density ranges. They are also used to compare relative material thicknesses.
  • Densitometer are used for process control of density dot gain, dot area &ink trapping
  • Densitometer reading will be different types of printing process &substrate


Industrial Tomography Systems (ITS)[5] has collaborated with a leading European dredging contractor to develop their radiation and gamma free Dens-itometer[6] based upon Electrical resistance Tomography. The system utilises electrical conductivity, to provide a greener, simpler, more cost effective alternative to conventional nuclear based systems.[7] ITS pipe based sensors provide real time visual data on the processes occurring within the pipe.

The environmentally friendly Dens-itometer is making waves in the dredging and mining sector,[8][9] as it can take measurements independent of flow regime and obtain readings of materials which are neutrally buoyant. The Dens-itometer has been tested on slurry conveying with 100,000s of tonnes of materials having been processed and delivering data consistent with gamma densitometers. It has also been deployed in food processing as a basis for measuring solids content in pipelines.[10]

See also


  1. "301 Medical Densitometer - Black & White Film Measuring". X-Rite. Retrieved 2014-08-23.
  2. "Unbound MEDLINE : An evaluation of a rotating drum densitometer and its application to precession photographs of protein crystal". Retrieved 2014-08-23.
  3. Health Physics Division annual progress report. Oak Ridge National Laboratory. Health Physics Division, Union Carbide Corporation, U.S. Atomic Energy Commission, United States. Energy Research and Development Administration, United States. National Bureau of Standards. Fracture and Deformation Division, United States. Dept. of Energy. Office of Fusion Energy, United States. National Bureau of Standards. p. 101. Retrieved 2014-08-23.
  4. Singh, S. K. (2003). Industrial Instrumentation & Control (2nd ed.). Tata McGraw-Hill Education. p. 451. Retrieved 2014-08-23.
  5. Industrial Tomography Systems,
  6. Industrial Tomography Systems,
  7. Port Technology,
  8. J. Butterworth,
  9. Dredge mag,
  10. Industrial Tomography Systems,
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