Expert: Dana Krempels, Ph.D. - 9/8/2007

Question
My introductory college anatomy/physiology course had its first and only histology lab last night.  All prepared slides were viewed with a 10x ocular and 43x objective, giving a total magnification of 430X.

Two questions:
1.  are most lab microscope oculars 10X?  This seems very common from the 'scopes I've seen advertised online.

2.  What is the width of a 430X field?  I know I could use the table movement dials to measure it, but perhaps not all microscopes have movable tables.  I might want to used a fixed magnification 'scope for field work, and it would be useful to be able to estimate the size of the field from knowing only the magnification.   In general, and without using a calibration reference, how does one determine the field width (or object size) given the magnification factor?

Thank you!

Answer
Dear John,

The answer to #1 is yes.  Most (but not all) oculars are 10x magnification.

Number 2 is a little more complicated, as different oculars and objectives have different apertures.  But you can use a simple formula to calculate the field of view, if (as with most 'scopes) your microscope's apertures are listed on each of the lenses.  Instructions for calculations can be found here:

http://www.microscopyu.com/articles/formulas/formulasfieldofview.html

An extemely simple (if not as accurate) way of doing this is to place a translucent mm ruler in the field of view, and estimate the diameter from the ruler itself.  

Hope that helps!

Dana