Imaging White Papers

How To Calculate Total Magnification

White Papers on Digital Pathology, Macro, and Microscope Imaging
Contact a
SPOT Imaging Specialist

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