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How to mesure the HFOV ?

Now you can take the picture of the specimen or make a



For trying this for the first time the simple way is :

first test of your scale image by making a proportional



after taking a good picture of a specimen take another one of a scale.

resample of :  4500 x 3375 pixels.



If the objective is 40x or more use a stage micrometer of 1 mm

You have now a calibrated image where each 10 pixels,



If the objective is 2x, 4x or 10x you can use a micrometer of 10 mm

on the specimen picture, is equal to 1 μm .



design for eyepiece. It is better if your scale cover all the horizontal

Now you are ready for crop a small or big object 



view of the picture.

in the picture for evaluate the dimension in micron.







Never crop the picture of the specimen before making mesurement.



With a software like Photoshop make a high resample 



of the picture of the scale  by  8000 x 6000 pixels.



Crop the scale image for showing a round number of divisions :



10 divisions = 0.1 mm    or    20 divisions = 0.2 mm 



Now look on the property of the image for see the number of pixels



for the width. If the picture of your scale was taken with a 40x



you will obtain about 3555 pixels for 20 divisions or for 0.2 mm.



3555 pixels = 0.2 mm    then    8000 pixels = 0.450 mm

New resample of a scale

       Crop picture



The HFOV  for this lens in this particular condition is :  450 μm 

Objective 40x

       20 divisions : 200 μm




4500 x 3375 pixels

       2000 pixels



















 Full picture of a scale

        Crop picture



 Objective 40x

   20 divisions : 0.2 mm =  200 μm



 8000 x 6000 pixels

        3555 pixels