Microscope Eyepieces – Magnification, Field of View, and Fit.


Magnification: Eyepieces come in different magnifications. The most commonly used is the 10x magnification. The majority of pre-configured microscopes come with 10x eyepieces. The major manufacturers such as Nikon, Olympus, and Leica make eyepieces in 15x and 20x for increased magnification. The trade off is that the higher the magnification, a smaller the field of view, and the more costly the eyepiece.

When calculating total magnification, we multiply the power of the eyepiece by the power of the objective. (and any intermediate or auxiliary lenses.) In the Nikon CFI 10x/22 eyepiece pictured above, the magnification is 10x. To determine the total magnification used with a 40x objective, we simply multiply the 10x by the 40x to get a total magnification of 400 times under a 40x objective.  If you don’t specifically need an increase in magnification, then stick with 10x eyepieces and the wider field of view.

Field of View: Eyepieces use a “Field of View” number often given in millimeters to measure the complete field of view when used in conjunction with the different objectives on a microscope. Eyepieces typically come sized with 18mm, 20mm, and 22mm field of view numbers. The field of view should always be in concert with the field number of the objectives used.  If you us an eyepiece with a 22mm field of view and an objective with a 20mm outside field number you will get a halo effect when looking through the microscope at low power. It is highly recommended that you consult an authorized microscope representative to make sure the eyepieces you are buying are matched correctly to your corresponding objectives.  The bigger the field number, the larger the field of view. To calculate field of view you can visit the chart in the link.

Physical Fit: The eyepiece must physically fit into the eyepiece tube. Not all 10x/22mm eyepieces are the same. The eyepiece in the picture above fits a Nikon Ci-L microscope head. This eyepiece is proprietary to Nikon’s heads because there are little notches to keep the eyepiece from spinning when using the diopter.

Eyepiece Micrometer: Lastly, the other number that comes into play when looking at an eyepiece is the micrometer size. Most high quality eyepieces accept micrometers.  This micrometer size typically ranges between 18mm and 27mm. This size is typically only available from the manufacturer. The round glass eyepiece micrometer (sometimes referred to as a reticle) is installed through the bottom of the eyepiece and is held in place with a retaining ring. Micrometers are available in a wide variety of types and sizes for counting and measuring.

Closing Recommendation: My advice would be to size your eyepieces according to the manufacturer’s recommendation per the particular model microscope you are using. Interchanging eyepieces can reduce optical quality. Consult a reputable microscope dealer for guidance, now that you have a basic overview of what to look for in an eyepiece.

Microscope for College and University Labs (On a Budget)

Q: College Lab Manager:  Which binocular microscope would you recommend for the multi-user environment of the college laboratory setting?

A: Microscope Consultant:  Taking three things into consideration, price, optical quality, and durability, I would recommend the Nikon Eclipse 200 LED.

The Olympus CX-31 would be a close second, but costs more than the Nikon E200.

With a list price of $2,038.00 USD, the Nikon Eclipse 200 LED does not fit into every colleges budget. So we then look at the second tier microscope companies such as Accu-scope, Labomed, and WP. The second tier microscope companies make solid microscopes that focus on economics before optical quality.

The newest model offered by WP is the 3008-L3 college level binocular microscope.

Bang for your Buck

Better Objective Package: This microscope comes complete with a 4x, 10x, 20x, 40x, and 100x, Oil Plan Objective package. This trumps the competition who offer four objective packages due to the limiting four hole nosepiece.

Wider Field of View: The WP 3008-L3 provides 10x objectives with a true 22mm field of view. This trumps the competition by providing a wider field of view for students. 22mm field of view is the typical field number you find in next level clinical microscopes used on the professional level.

Better Mechanical Stage: The WP 3008-L3 comes standard with a right handed graphite mechanical stage. The graphite makes this stage scratch resistant.

Better Illumination System: The WP 3008-L3 comes standard with a energy saving variable LED illumination system which is superior to the old halogen illumination system found in other brands of microscopes. Greener technology and no more “replacement lamp” costs = $ savings for bulk users.

Better Condenser: The WP 3008-L3 comes standard with a 1.25 Abbe condenser. The diaphragm control is marked with each magnification to ensure that students are obtaining the optimal image.

Storage Friendly: The WP 3008-L3 comes with a built in cord wrap and 360 degree rotatable head. This allows for the 3008-L3 to fit comfortably into storage cabinets.

Of course the 3008-L3 comes with all the standard options that your typical college microscope comes with. A 5 year limited warranty from the manufacturer allows for you to buy with confidence.


The 3008-L3 is a legitimate contender for “best low cost college level microscope of 2015” in our opinion.  As always, it’s best to cost shop all microscopes based on the microscope model so you know that you are getting an apples to apples comparison on price. As always, with educational institutions, make sure you request your educational discount. Most microscope companies will also include free shipping. The 3008-L3 is a simple assembly straight out of the box which does NOT require a qualified microscope service company to set up. Most microscope companies now provide written quotes via email from their websites.

Diopter – Why adjustable eyepieces are important when buying a microscope.

Your eyes are different from my eyes. In fact, my left eye sees differently than my right eye. This is typical in most human beings. So when you look through a microscope, your right eye is seeing your specimen with a different degree of sharpness than your left eye. By allowing the microscope user to adjust the eyepiece through the use of a diopter, the user can sharpen the focus of the specimen to a finer degree customized to their own eyes.

Adjustable eyepieces are essential to an image’s sharpness. When purchasing a microscope, you should insist upon a microscope where both eyepieces are adjustable.

The good news is that most of the high quality microscope manufacturers, like Nikon and Olympus, provide the option for adjustable eyepieces. In fact, Nikon’s current clinical line of microscopes only come with adjustable eyepieces. When buying microscopes for your lab, make sure that both eyepieces are adjustable.

How to make a 20mm Infinity Objective fit the Nikon 25mm thread pattern Eclipse Microscope Series.

The question arose the other day in a scan of the microscope forums on Yahoo. The user wanted to know if he could use his rather expensive Olympus 100x Oil Objective on a Nikon microscope.

The nosepiece thread pattern for Nikon Eclipse series microscopes is 25mm. (with the exception of the Nikon Eclipse 100 LED which is the standard RMS threading of 20mm)

The thread pattern for Olympus Infinity objectives is 20mm RMS. There in lies the problem.

SEO Enterprises, Inc Microscope Sales and Service is now making available a step down adapter that reduces the thread size of the 25mm Nikon to the 20mm thread pattern of most microscopes, including Olympus, Meiji, and Accuscope.

The Nikon Adapter is available on their website.

How do I connect my Nikon DSLR camera to my Nikon Microscope?

How do I connect my Nikon DSLR camera to my Nikon Microscope?

Connecting a camera to a microscope requires a specialized set of adapters.

The adapters not only attach the camera to the trinocular microscope head, but they will often act as an auxiliary lens.


You will need:

– 1 Nikon DSLR Camera

– 1 Nikon Trinocular Microscope (E200, E400, E600, 50i, 55i, 80i, 90i)

– 1 Nikon F Mount

– 1 Nikon F Mount TV Tube 

The F Mount will mount to your Nikon DSLR Camera body in place of your lens. The F mount slides into the F Mount TV Tube and it is held in place by set screws so that your DSLR camera points down the tube. You will then mount the F Mount TV tube to the trinocular port of your microscope.

The F Mount uses nodules that will allow your Nikon DSLR camera to  meter the image correctly.

Once you have the proper adapters, the set up is simple and the images come out fantastic. If your DSLR camera comes with a USB cord, you can hook it directly to a computer to capture digital images and video of your specimen.



How to calibrate a stereo microscope.

How do I complete the initial focus set up on a stereo zoom microscope

 1) Center your specimen on the stage for observation.

2) Adjust your lighting so that the specimen is properly illuminated on the stage.

3) Set your adjustable eyepiece(s) to 0. Your dot (marking) on the eyepiece collar should match up with the 0.

4) Set your zoom to the highest power.

5) Use the focus block to bring your specimen into focus.

6) Using your right eye only, look through the eyepiece on the right side and focus it so that the image is at it’s sharpest.

7) Using your left eye only, look through the eyepiece on the left side and focus it so that the image is at it’s sharpest.

8) Rotate your zoom knob to the lowest power. Your microscope should now be calibrated so that your specimen is in focus throughout the entire zoom range.