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How To Calculate Total Magnification

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How To Calculate Total Magnification

This article describes how to calculate the effective magnification and the size of your sample on your monitor when using a digital camera on a microscope.

Magnification on the TV Monitor

In order to determine the total magnification on the TV monitor, the following variables must be known:

  1. Objective magnification
  2. Microscope adapter magnification.
  3. CCD chip diagonal dimension
  4. TV monitor diagonal dimension

The formula used to calculate total magnification on the TV monitor is:

Total Magnification = Objective Magnification x Microscope Adapter Magnification x Video Magnification

The video magnification is determined by dividing the TV monitor diagonal (mm) by the CCD chip diagonal (mm). A reference chart is given below which shows video magnification for various monitor and chip sizes. To determine "Video Magnification" on a computer monitor divide the actual image diagonal (as measured on the screen) by the CCD chip diagonal.

  9" 12" 13" 19" 20" 27"
1/3" 38.1x 50.8x 55.0x 80.4x 84.7x 114.3x
1/2" 28.6x 38.1x 41.3x 60.3x 63.5x 85.7x
2/3" 20.8x 27.7x 30.0x 43.9x 46.2x 62.3x
1.0" 14.3x 19.1x 20.6x 30.2x 31.8x 42.9x

What is the magnification on the TV monitor when using a 10X objective, 0.45x video coupler, a 1/2" format CCD and a 19" monitor?

482.6 mm (19" diagonal)
------------------------------
8 mm chip diagonal
Total Magnification = 10 x 0.45 x
= 10 x 0.45 x 60.3
= 271.35

Determining the Size of Your Specimen

The approximate real size of a specimen can be determined by dividing the length of the specimen measured on the monitor screen by the total magnification on the monitor.

Length of Specimen Measured on Monitor Screen
----------------------------------------------------------------------
Total Magnification
Real Size of Specimen =

In the above example, if the measured length of a specimen was 100 mm, the real size of the specimen would be:
Real Size of Specimen = 100 mm / 271.35
= 0.37 mm