World Library  
Flag as Inappropriate
Email this Article

Densitometry

Article Id: WHEBN0001989200
Reproduction Date:

Title: Densitometry  
Author: World Heritage Encyclopedia
Language: English
Subject: Hurter and Driffield, Optical metrology, Platinum print, Absorbance, Northern blot
Collection: Optical Metrology
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Densitometry

Densitometry is the quantitative measurement of optical density in light-sensitive materials, such as photographic paper or photographic film, due to exposure to light. Optical density is a result of the darkness of a developed picture and can be expressed absolutely as the number of dark spots (i.e., silver grains in developed films) in a given area, but usually it is a relative value, expressed in a scale.

Since density is usually measured by the decrease in the amount of light which shines through a transparent film, it is also called absorptiometry, the measure of light absorption through the medium. The corresponding measuring device is called a densitometer (absorptiometer). The logarithm of the reciprocal of the transmittance is called the absorbance or density.[1]

DMax and DMin refer to the maximum and minimum density that can be recorded on the material. The difference between the two is the density range.[1] The density range is related to the exposure range (dynamic range), which is the range of light intensity that is represented by the recording, via the Hurter–Driffield curve. The dynamic range can be measured in "stops", which is the binary logarithm of the ratio of highest and lowest distinguishable exposures.

Contents

  • Uses 1
  • See also 2
  • References 3
  • External links 4

Uses

According to the principle of operation of the densitometer, one can have:

  • spot densitometry: the value of light absorption is measured at a single spot
  • line densitometry: the values of successive spots along a dimension are expressed as a graph
  • bidimensional densitometry: the values of light absorption are expressed as a 2D synthetic image, usually using false-color shading

Dual-energy X-ray absorptiometry is used in medicine to evaluate calcium bone density, which is altered in several diseases such as osteopenia and osteoporosis. Special devices have been developed and are in current use for clinical diagnosis, called bone densitometers.

See also

References

  1. ^ a b Davies, Adrian (2005). The Focal Digital Imaging A-Z.  

External links

  • Fundamentals of Densitometry, by Mark Vivino.
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.