Microscopes are fun to use but can sometimes be frustrating if you don’t know how to bring something into focus. Knowing the limits of the microscope and knowing some of the common mistakes and things to troubleshoot can save you some time a grief. So how does one focus a microscope?
To focus a microscope, rotate to the lowest-power objective, and place your sample under the stage clips. Play with the magnification using the coarse adjustment knob and move your slide around until it is centered. When switching to a higher-power objective, focus using the fine adjustment knob until the edges, and specific features of interest become sharp and clear.
This article will cover the ins and outs of focusing a microscope and some common issues encountered when trying to focus on a specimen. It will also detail some of the differences between wet and dry mount slides and the parts of a microscope involved in act of focusing a microscope.
Focus on a Prepared Slide
Pre-prepared slides are slides that have specimens already collected for you locked inside of them. You can buy them off of Amazon from companies like National Geographic or Celestron, such as this Celestron Prepared Microscope Slides (100-Piece Set).
Focusing on a slide takes patience. You may find yourself tempted to turn to the highest power objective and start twisting both focus knobs right away. But resist the temptation.
Whether focusing on a dry or wet mount slide, always start on the lowest power objective. By putting a microscope on high power, you are basically “zooming in” on the specimen, making it easier to overlook important areas and making it harder to find the sample in your field of view. Focus using the coarse adjustment knob first, then make adjustments with the fine adjustment knob later on higher power objectives. If you want to go to a higher power objective, do so, then focus again with the fine focus knob only.
If you use the coarse adjustment knob under a higher power objective the stage may raise or lower too rapidly for you to ever bring the microscope into focus and resolve the image. Additionally, you risk damaging the objective lens if you use coarse adjustment because you could raise the stage too rapidly and accidently press the slide into the objective. Objectives are one of if not the most expensive piece of the microscope so you definitely want to avoid this!
Steps to Focus a Microscope
- Rotate to the lowest-power objective lens. You want to make sure that you can look through the lens without being too concentrated on one area. If it’s too powered, you won’t be able to make out anything through the lens. Rotate it down, then proceed to the next step.
- Place your slide label-side up on the stage: clip it on with the stage clips. Every microscope comes with one or more clips that can be used to hold slides. Never try to use DIY clips since they’re not stable. Stage clips are designed to hold the delicate glass slides without causing damage.
- Use the coarse focus knob to focus on your slide as best you can. Take your time and make sure that the lens isn’t too close to the slide. Contrary to popular belief, getting too close to a microscope or sliding it too close to the lens can make it harder to see. It reduces the field of vision.
- If nothing can be seen, try using the X-Y translational knobs to move the slide until you see the specimen, then try reducing the light source – this can be done by closing the iris the diaphragm below the stage. You never know if the slide isn’t centered unless you look with your eyes rather than the microscope. If it’s off-center, you’ll never get a glimpse.
- If you are seeing some spherical aberration try using a green filter. You can use a filter by swinging out the filter rack below the stage, placing the filter into the rack and then re-engaging the filter rack back into place. For more on microscope filters see this post.
- When done looking at low power, rotate to the medium or high-power objective lens, then focus using the fine focus knob. You’ll be able to see much more of the specimen in higher detail.
This video will show you step by step how to use a microscope including focusing the microscope.
That’s all there is to it! Focusing a microscope is fairly simple once you know how to follow the previously mentioned six-step process. Keep in mind that, when using a microscope, it’s important to take your time and move slowly. Sudden changes can cause drastic alterations to the slide and what you’re able to see.
If you have any other questions about how to focus a microscope or you’d like to see general tips on the topic, read on.
Microscope Focusing FAQ
- I can see nothing; everything is dark. Make sure your microscope is plugged in and switched on, and all the objective lenses are screwed on properly. Also, check the light source and see if it is working, or if the light burned out. You might have luck using another light source.
- I can’t find anything on low power. Make sure you’ve centered the slide and turned the coarse adjustment knob to see if anything comes into focus. Off-center slides are the most common culprit. Look from all sides to ensure that the slide is perfectly centered, then take another look.
- When I switched to a higher power, everything disappeared. This means your slide is not centered. Return to the lower-power objective and center it properly.
- The image is blurry on all powers. Clean your objective lens. Small scratches could permanently blur your lenses, so use caution when moving the microscope or raising the stage too high. Consider getting a carrying case if you don’t already have one.
- The image is blurry on one particular power. Clean that objective lens with lens paper. Again, scratches might be the cause of the issue. Wipe it down, buff it out, and see if you can get a clearer image.
- I see lots of circles with dark rings. These are air bubbles that were possibly caused by the procedure used to create the wet mount. For a complete guide on wet mounting slides see this post.
Limits of Magnification
The maximum useful magnification for microscopes is around 1000x-1200x due to the limits of the magnifying power of light. At a certain point, the image will keep getting bigger as you zoom in, but the resolution will stay equally as bad. To learn more about magnification see Microscope Magnification: Explained.
If you have engaged your highest power objective but are unable to bring it into focus that is because typically the highest power objective on a microscope is a 100X oil immersion objective. These objectives are specialized objectives that require the objective to have a drop of immersion oil between the objective lens and the slide coverslip over the specimen on the slide. You will not be able to focus this objective without immersion oil. For a complete guide on how to use immersion oil and for the reason why you need immersion oil to bring something into focus with this objective see this post.
Focusing a microscope isn’t too hard if one follows the suggestions laid out in this article. Always start out on the lowest-power objective and use the coarse focus knob first. Focusing on wet and dry mount samples works the same way, although preparing them is different.
Do not use excessive magnification, as the zoom will increase while the resolution will not. If you are still having no luck focusing your microscope, consider taking it in for repair. Small scratches on the lens or corroded knobs can alter its performance. You could save quite a bit of time and money by calling a professional to take a look. Follow the proper maintenance procedures and your microscope will last for many years to come.
Look through the eyepiece (1) and move the focus knob until the image comes into focus. Adjust the condenser (7) and light intensity for the greatest amount of light. Move the microscope slide around until the sample is in the centre of the field of view (what you see).How do you focus the microscope to see clearly? ›
Look through the eyepiece (1) and move the focus knob until the image comes into focus. Adjust the condenser (7) and light intensity for the greatest amount of light. Move the microscope slide around until the sample is in the centre of the field of view (what you see).How do you make a microscope clearer? ›
Adjust the coarse focus knob.
Begin to focus on the object by adjusting the coarse focus knob. This will be the larger of the two knobs on the side of the microscope. Rotate the knob clockwise and counterclockwise until you see the best possible picture through the eyepiece.
The primary factor in determining resolution is the objective numerical aperture, but resolution is also dependent upon the type of specimen, coherence of illumination, degree of aberration correction, and other factors such as contrast-enhancing methodology either in the optical system of the microscope or in the ...How do you sharpen the focus on a microscope? ›
The best way to accomplish this is by first bringing the front of the objective to about 5 mm from the slide's surface. Constrict the luminous-field diaphragm, and then, looking through the eyepieces, increase the distance between the specimen and the objective until the image appears sharp.How do you focus the lens to ensure a quality image? ›
- Know your focal points. ...
- Focus first, then recompose. ...
- Find a line. ...
- Use the correct focus mode for your situation. ...
- If in doubt, focus on the foreground subject. ...
- Use aperture priority mode. ...
- Avoid shooting in low light.
Image Out of Focus, Hazy or Unsharp - A lack of proper focus and/or blurry images represent one of the most common errors in photomicrography. The source of these errors is usually the result of vibration in the microscope stand or improper adjustment of the focal distance between the optics and the film plane.What part of a microscope makes the image clearer? ›
Condenser Lens: The purpose of the condenser lens is to focus the light onto the specimen. Condenser lenses are most useful at the highest powers (400x and above). Microscopes with in-stage condenser lenses render a sharper image than those with no lens (at 400x).What are the factors of clarity? ›
There are five factors that affect how clarity is determined in a diamond, and how inclusions are considered; size, nature, number, location, and relief. Generally, the larger the inclusion, the greater the impact on the clarity grade.What is the best resolution for a microscope? ›
The best resolution for an optical microscope is about 0.2 microns = 200 nm.
The three important factors of microscopy include: Illumination: Illumination of the object or the material that is placed on the microscope stage. Focusing: Focusing the object on the stage. Magnification: Magnifying the microscope based on the requirements for viewing the object clearly.How can I improve my focus and sharpness? ›
- Eliminate distractions. How do we focus better if we are always bombarded with information? ...
- Reduce multitasking. ...
- Practice mindfulness and meditation. ...
- Get more sleep. ...
- Choose to focus on the moment. ...
- Take a short break. ...
- Connect with nature. ...
- Train your brain.
Simply put, if you do not enlarge the microscope image enough, you will not be able to see what is present – and may miss smaller filaments. Solution: Start with 100x and focus in on your image then, move to 400x for image capture.
The process of getting a sharp and clear image of an object from an optical device is called focussing. In a simple microscope, focussing is done by adjusting the position of both objective and eyepiece. Objective lens is used for coarse focussing and eyepiece is used for soft focussing.How do you adjust a microscope if the image is blurry? ›
First, focus the image using the coarse and fine focus adjustment while looking down through the eyepiece of the microscope. The best way to precisely adjust the focus is with the optical viewfinder and the fine focus adjustment knob of the microscope.What focus setting should I use? ›
Single-Point AF is the best focus area mode for still subjects. Landscape photography makes regular use of this mode, since the portions of the landscape you're using to focus on won't be moving. This focus area also gives you more accuracy when you're shooting a portrait or image where the exact focus point is vital.How do you check lens focus accuracy? ›
- Place the card in a well-lit area, somewhere your camera will find it easy to focus on the card. ...
- Now, place your camera the correct distance from the test card, 50 times the focal distance of the lens. ...
- Open the aperture on your lens up to its widest.
- Now, manually focus the lens to infinity.
Focus (coarse), The coarse focus knob is used to bring the specimen into approximate or near focus. Focus (fine), Use the fine focus knob to sharpen the focus quality of the image after it has been brought into focus with the coarse focus knob.How do you ensure clarity? ›
One way to ensure clarity in our communication is to be specific. Don't make it any more difficult for the other person to understand what you are saying than is absolutely necessary. Don't use big words when small ones will do. Avoid using terms and phrases that could mean different things to different people.How do you maximize clarity? ›
- Get enough quality sleep. How much sleep you get is directly proportional to how much energy you will have throughout the day. ...
- Manage your stress. ...
- Practice mindfulness. ...
- Find a work-life balance. ...
- Practice self-care. ...
- Move your body. ...
- Maintain a healthy diet. ...
- Ask for help.
- Create some space. When we're unclear on something (how we should reach a goal, for example) … ...
- Journal, iterate. ...
- Meditate & contemplate. ...
- Talk to others. ...
- When you have a little clarity, write it down. ...
- Take action to get clarity. ...
- Reflect after you take action & get clearer.
Spectral precision distance microscopy (SPDM)
This achieves an effective optical resolution several times better than the conventional optical resolution that is represented by the half-width of the main maximum of the effective point image function.
In reality, therefore, microbiologists depend more on resolution, as they want to be able to determine differences between microbes or parts of microbes. However, to be able to distinguish between two objects under a microscope, a viewer must first magnify to a point at which resolution becomes relevant.What light has better resolution in microscopy? ›
The greatest resolving power in optical microscopy is realized with near-ultraviolet light, the shortest effective imaging wavelength. Near-ultraviolet light is followed by blue, then green, and finally red light in the ability to resolve specimen detail.Why do some microscopes give clearer images than others? ›
Microscope lenses differ widely in quality, and this can affect how clearly you can see an image. The quality of the glass used and the shape of the lens both affect its overall quality. Misalignment of lenses within the microscope can also limit resolution.What are the 3 important techniques in basic microscopy? ›
There are three main branches of microscopy: optical microscopy, which is divided into many sub-techniques, electron microscopy, and scanning probe microscopy. These are not the only techniques in existence, but they are the best-known and most commonly-used.What 2 factors are important for microscopes? ›
Two important microscope objective characteristics are field number and depth of field. The field-of-view number, or field number, is the diameter of the field of view in your optical microscope.Why can't I focus clearly? ›
Causes for Difficulty Focusing Eyes
Refractive errors (the most common cause) Age-related macular degeneration. Cataracts. Diabetic retinopathy.
Mindfulness, cognitive training, and a healthy lifestyle may help sharpen your focus.Why can't I see sperm under microscope? ›
Sperm samples are transparent and can be difficult to see with a standard microscope. Normally, transparent samples are stained to make them easier to see but the process can damage or kill living organisms or cells.
Three common errors associated with this are: first, high magnification ; second, changing techniques; third, lack of practice. Based on these common errors, three main principles in the use of the operating microscopes are recommended as guidelines for surgeons who are adjusting to the operating microscope.Why do I only see white through my microscope? ›
The sample is of too low concentration
This means that you are only observing a clear liquid without many cells or other particles. As a general rule of thumb, if you are able to see through the sample without any problems, then you will also not be able to see anything under the microscope.
Aperture and depth of field
Aperture and image sharpness are closely related. Wide apertures and sharpness: When we use wide apertures, the depth of field drastically decreases. This means that just a very small area of our image will be acceptably sharp.
Aperture The aperture of your lens has a definite effect on image sharpness. Each lens has a “sweet spot” aperture that provides maximum sharpness. This is, generally, two or three stops from the lens's widest aperture. Therefore, an f/2.8 lens will have a sweet spot around f/5.6 or f/8.What should you do if your slide looks blurry under a microscope? ›
Problem #5: The image is blurry on all powers.
Clean the microscope's ocular lens. (Only use lens paper!) If you rotate the ocular and the specks move, there is dirt on the ocular lens and it should be cleaned.
Turn the coarse focus knob slowly until you are able to see the cells. Turn the fine focus knob slowly until the cells are in focus and you can see them clearly.What is used for focusing to get a clearer view of the specimen? ›
Condenser Lens: A lens mounted in or below the stage. The purpose of the condenser lens is to focus or condense the light onto the specimen.What part of microscope is clearer focusing? ›
Condenser Lens: The purpose of the condenser lens is to focus the light onto the specimen.What are the 5 steps in focusing on a microscope? ›
- Set to low power and lower stage with coarse knob.
- Put slide under stage clips.
- Center slide over light source with x,y knobs.
- Use coarse knob until object is in focus.
- Rotate diaphragm for appropriate amount of light.
- Use fine knob to focus.
- COMPLETELY center object in field in view.
- Move to next highest objective.
Calibrate in the center of the screen
Since the lens becomes more distorted the farther it is from the center, using points closer to the center yields higher accuracy. If you use the entire distance, or if you use only the end, it's easy for errors to happen.
Electron microscopes differ from light microscopes in that they produce an image of a specimen by using a beam of electrons rather than a beam of light. Electrons have much a shorter wavelength than visible light, and this allows electron microscopes to produce higher-resolution images than standard light microscopes.What brings the specimen into the best focus? ›
Coarse Adjustment Knob- The coarse adjustment knob located on the arm of the microscope moves the stage up and down to bring the specimen into focus.What is used to bring an object on the microscope into clear focus? ›
Use the coarse adjustment to bring the object into focus. Always turn the coarse focus knob so the objective lens moves away from the stage, so that you do not break the slide or damage the lens. Never use the coarse adjustment to focus closer to the object while looking through the eyepiece.What is the clarity of an image in a microscope? ›
In microscopy, the term “resolution” is used to describe the ability of a microscope to distinguish details of a specimen or sample. In other words, the minimum distance between 2 distinct points of a specimen where they can still be seen by the observer or microscope camera as separate entities.How does microscope focus work? ›
A simple light microscope manipulates how light enters the eye using a convex lens, where both sides of the lens are curved outwards. When light reflects off of an object being viewed under the microscope and passes through the lens, it bends towards the eye. This makes the object look bigger than it actually is.What is the first step in focusing the microscope? ›
Focusing the Microscope:
Start by turning the revolving nosepiece (turret) so that the lowest power objective lens is "clicked" into position. The lowest power objective is the shortest one. This objective is the easiest to focus and center the image in the field of view.
It's important to start with the lowest magnification possible so you can easily find the specimen on the slide and gradually focus it before increasing the magnification to see the specimen more closely.