User Guide
18
120
Series
T
echnica
l
Parameters
Technical Terms & Concepts 
Total Magnification
Total magnification of a microscope is calculated by the magnification of the objective multiplied by the
magnification of the eyepieces. 
-Ex: (10x Eyepieces) x (4x Objective) = 40x Total Magnification 
Field of View
Linear field of view of the eyepiece divided by the magnification of the objective 
Numerical Aperture (N.A)
Calculated  by  n  Sin 
α
  (max),  the  Numerical  Aperture  (N.A)  is  an  important  parameter  that  marks  the 
features  of  the  objective  and  condenser’s  image  quality  and  resolution.  The  “n”  is  a  refractive  index  of  the 
medium
(air or immersion cedar oil) between the objective lens and the specimen. The “
α
” is 1/2 of the angle 
between  the
aperture on  the  objective and  path  of  light.  The  larger  the  N.A, the  higher  the  resolution  of  the 
objective (and better  quality of the image) is. 
Object to Primary Image Distance
The distance between the object plane and the primary image plane. The conjugate distance is fixed. 
Mechanical Tube Length
The distance between the objective shoulder and the ocular shoulder 










