Calculating the Magnification and Sample Size on the Monitor Screen

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 know:

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 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