![\"Fine](\"https:\/\/scopedetective.com\/wp-content\/uploads\/2021\/01\/microscope-stage-focus-knobs.jpg\")
These knobs are also known as the \u2018stage adjustment knobs\u2019 because they literally adjust the stage up and down.<\/p>\nCompound microscopes have fine and coarse focus knobs which are used to \u2013 of course \u2013 achieve focus on the specimen.<\/p>\n
These knobs are also known as the \u2018stage adjustment knobs\u2019 because they literally adjust the stage up and down.<\/p>\n
In this article, I\u2019ll outline everything you need to know about the focus knobs on a microscope, including:<\/p>\n
Let\u2019s get started!<\/p>\n
> This article is from our series on the Parts and Functions of a Microscope<\/a><\/p>\n\n As the stage gets closer or farther away from the objective, the focus on the specimen will change.<\/p>\n It\u2019s much like when a person who has poor vision moves a book closer and farther from their eyes until they can read the text. Microscopes don\u2019t have \u2018auto focus\u2019, so you need to do the focus manually.<\/p>\n The focus knobs on a microscope are located at the base of the arm of the microscope, behind the stage. There is usually one on each side, although some microscopes only have a microscope on the right-hand side.<\/p>\n In general, I find microscopes with a focus knob on each side to be the easiest to work with. I usually control it with both hands \u2013 one on each side. It\u2019s just the most comfortable approach for me.<\/p>\n The fine and coarse focus knobs are usually actually on the same knob. You will be able to turn the whole knob if you grab it by the base and turn it. Or, you can turn just the tip of the knob if you just grab the tip!<\/p>\n The coarse focus knob will be the section at the base which makes larger movements, while the fine focus knob will be the section at the tip which makes smaller movements of the stage. You can see both in this image:<\/p>\n Most microscopes have a coarse and fine focus knob. However, some microscopes only have a coarse focus knob if they are entry-level beginner microscopes.<\/p>\n The coarse focus knob is the knob which moves the microscope stage a larger distance per rotation.<\/strong><\/p>\n The purpose of this knob is to get roughly close to the correct focus on the specimen.<\/p>\n Usually, you use the coarse focus knob first and then improve the focus more by reverting to the fine focus knob.<\/p>\n But the coarse focus is also useful for pulling the stage right down for changing specimens and moving the stage to remove the condenser that sits under the stage.<\/p>\n Because the coarse focus knob moves the stage a larger distance per rotation, it can be hard to perfect the focus with that knob. You\u2019ll move it a tiny bit and you might jump over the best focus.<\/p>\n So, while the coarse focus knob is excellent for getting close to the right focus, once you\u2019re close, you need to use the fine focus knob to get the right focus.<\/strong><\/p>\n Usually, the fine focus knob moves at about one tenth the speed of the coarse focus knob. So, it allows you to make very fine focus adjustments.<\/p>\n With the high power objective, even getting focus on the specimen with the fine focus knob is hard. The depth of the specimen often means you can only look at it in \u2018layers\u2019 \u2013 the whole specimen won\u2019t be in focus at any one point in time.<\/p>\n After placing your slide onto the stage, it\u2019s time to use the focus knobs. Here are the steps involved:<\/p>\n Below is a photo of a 4x scanning objective. Notice the red stripe which is a universal indicator of a scanning objective:<\/p>\n > Read Also: What are the Objective Lens Band Colors?<\/a><\/p>\n The objectives on a microscope contain lenses that can get damaged, scraped or even break if they bump up against the stage or specimen too hard.<\/p>\n There are two main ways you can protect your objectives when in use.<\/p>\n First, ensure you get spring loaded lenses.<\/strong> From the high power (40x lens with blue stripe) and up, you should ensure your lens has an \u2018s\u2019 (for spring) or \u2018r\u2019 (for retractable) marked on it. It will read: 40xs or 40xr.<\/p>\n Some don\u2019t have the marking \u2013 but you can tell it\u2019s spring loaded by simply pushing on the end and seeing if it retracts.<\/p>\n Spring loaded lenses will retract when they hit up against the stage or specimen to protect the lens from damage.<\/p>\n Second, only use the fine focus knob from 10x and up. <\/strong>The coarse focus knob is good for getting an approximation of focus when using the red striped 4x scanning lens. But above this, I recommend using fine focus to minimize the chances of a big hit between the stage and lens. (Still be careful \u2013 there are no guarantees here!)<\/p>\n Third, use a stage stop. <\/strong>See below.<\/p>\n Some more advanced microscopes, such as my Amscope T490B, have stage stops. You\u2019ll find the stage stop in behind the coarse focus knob. It’s a small lever, as shown on the bottom-left of this image:<\/p>\n The stage stop is a tool that will help you remember a stage position.<\/p>\n Raise the stage to a position that has good focus for your specimen, then flick the stage stop on. Then, you can lower the stage to adjust the slide or swap slides, then raise the stage again.<\/p>\n The stage will only raise to the exact position it was before, but no higher.<\/p>\n It essentially allows you to cap out the highest position of a stage to \u2013 again \u2013 protect the objective, but also save your favorite magnification position.<\/p>\n Some microscopes have a tension adjuster located behind the coarse focus knob. This is something I rarely touch, but if you notice the adjustment knobs are too stiff or loose, you can adjust the tension with the adjuster. You may notice sometimes that the stage will start to fall from its set position. If this is the case, tightening tension with this adjuster may help rectify the issue.<\/p>\n You can see a tension adjuster on the image earlier in this article.<\/p>\n > Read More: Functions and Types of Microscope Stages<\/a><\/p>\n The coarse and fine focus knobs on a microscope enable you to adjust the focus of the microscope to get the best view of the specimen possible. Remember to use the coarse focus knob only with the 4x objective, and the rest of the time use the fine focus knob. It will help you get better focus but also help to protect the objective lenses from damage.<\/p>\n Further Reading<\/strong><\/p>\n Compound microscopes have fine and coarse focus knobs which are used to \u2013 of course \u2013 achieve focus on the specimen. These knobs are also known as the \u2018stage adjustment knobs\u2019 because they literally adjust the stage up and down. In this article, I\u2019ll outline everything you need to know about the focus knobs on …<\/p>\n1. What does the Stage Adjustment Knob Do on a Microscope?<\/h2>\n
2. Where to Find the Focus Knob on a Microscope<\/h2>\n
![\"microscope](\"https:\/\/scopedetective.com\/wp-content\/uploads\/2021\/01\/fine-coarse-focus-knobs.jpg\")
<\/p>\n3. Difference Between Coarse and Fine Adjustment<\/h2>\n
Coarse Focus Knob<\/h3>\n
Fine Focus Knob<\/h3>\n
4. How to Obtain Focus on a Microscope<\/h2>\n
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![](\"https:\/\/scopedetective.com\/wp-content\/uploads\/2021\/01\/scanning-objective-lens.jpg\")
<\/p>\n5. How to Protect your Microscope Objectives<\/h2>\n
6. Using the Stage Stop (aka ‘Rack Stop’)<\/h2>\n
![\"a](\"https:\/\/scopedetective.com\/wp-content\/uploads\/2021\/01\/microscope-stage-stop.jpg\")
<\/p>\n7. Using the Stage Tension Adjuster<\/h2>\n
Conclusion<\/h2>\n
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