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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:
- Objective magnification
- Microscope adapter magnification.
- CCD chip diagonal dimension
- 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 |