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how to find the field of view on a microscope

how to find the field of view on a microscope

answer:Since the field of view is a circle, the size of the field of view is it’s area. You would need to find the diameter of the field of view, using a transparent

1) Look at your microscope eyepiece. After the eyepiece magnification you will see a F.O.V, number.
(Example: 10x/22 The 22 is your Field Number)

2) Use the following formula to obtain the total diameter:

Formula = Field Number Divided by Objective Magnification

3) Multiply your Answer by 1000 to convert to Microns (or move the decimal 3 spaces to the right.)

We’ve taken the time to do the math for you and provide you with this chart. Simply find the intersection of your microscope objectives magnification and the eyepiece field number to determine the diameter of your field of view.

Eyepiece Magnification Eyepiece Magnification Eyepiece Magnification Eyepiece Magnification Eyepiece Magnification
Objective Magnifiation 18mm 18.5mm 20mm 22mm 25mm
2x 9mm 9.25mm 10mm 11mm 12.5mm
4x 4.5mm 4.625mm 5mm 5.5mm 6.25mm
10x 1.8mm 1.85mm 2mm 2.2mm 2.5mm
20x 0.9mm 0.925mm 1mm 1.1mm 1.25mm
40x 0.45mm 0.4625mm 0.5mm 0.55mm 0.625mm
50x 0.36mm 0.37mm 0.4mm 0.44mm 0.5mm
60x 0.3mm 0.3083mm 0.3333mm 0.3666mm 0.4166mm
100x 0.18mm 0.185mm 0.2mm 0.22mm 0.25mm
When you look through the lens of a microscope you see a circular area, the diameter of which is known as the field of view. To work out the field of view we need to know the field number and the magnification of the objective lens.

The field number is the diameter of the image area when seen under the eyepiece. This is often written on the side of the eyepiece, as shown on the right. In this case, the eyepiece has a field number of 20mm. So the image, when seen with the eyepiece only, has a diameter or 20 mm.


Consider the image on the right as seen through the compound microscope with the eyepiece shown above. The microscope field of view when the 10X objective lens is used is found with the following formula:

Field of View = Field Number (FN) ÷ Objective Magnification

Field of View = 20mm / 10 = 2.0 mm

The greater the magnification the smaller the field of view.

For example, if the field of view under low magnification using a 10X eyepiece and a 10X objective lens is 5mm the field of view when using a 40X objective lens would be
5mm X 10/40, which is 1.25 mm.

he diameter of the field of an optical light microscope is the field number, which is the diameter of the field view in mm measured at the intermediate image plane. The field number is typically listed on the microscope eyepiece. The microscope field of view is found with the following formula:

Field of View = Field Number (FN) ÷ Objective Magnification

If an auxiliary lens is being used on a stereo microscope, the magnification factor of this lens should also be employed in the equation by multiplying this with the objective magnification as shown below:

Field of View = FN ÷ (Objective Magnification x Auxiliary Lens Magnification)

Typically the lower the magnification of the eyepiece, the higher the FN is. So for example, a 5x eyepiece might have a FN of 26mm, while a 10x eyepiece may be 22mm and a 30x eyepiece may only have a FN of 7mm.

Microscope Field of View Image

The higher your magnification, the smaller the microscope field of view will be. If you think of looking at the above aphid through the microscope, if you were to zoom in to view only the leg of the aphid, your field of view would definitely be smaller, while the magnification is increased.

How to Calculate the Field of View in a Microscope


A light microscope allows the examination of tiny objects.Light microscopes can magnify objects by up to 1,000 times. These objects may be much too small to measure with a ruler, which makes knowing the size of the field of view — the size of the area visible through your microscope — a useful piece of information. Calculating the field of view in a light microscope allows you to determine the approximate size of the specimens that are being examined.

Set your microscope to its lowest magnification and note the magnification power. Position your slide scale — a microscope slide marked with measurements — or your clear ruler under your microscope. Bring the ruler or scale into focus.

Move the scale over so that a scale bar, or line on the ruler, is at the farthest left edge of the field of view. Estimate the number of scale bars and spaces that go across your field of view. Estimate the fraction of a scale bar remaining at the far right, if necessary. You should now have a measurement such as 1.5 millimeters.

Calculate the size of the field of view for higher powers of magnification for your microscope using the following equation: low power magnification divided by high power magnification times low power field diameter in millimeters.


Repeat your field of vision calculation for each new microscope, as the field of view may vary slightly between brands or individual units. Your magnification factor will be the power of the objective lens, which you can change to increase the magnification, times the power of the eyepiece.

how to find the field of view on a microscope?

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