What are the differences between stereo and compound microscopes?

Listen to podcast: [MH002] Should I buy a stereo or a compound microscope?

Two different kinds of light microscopes

Stereo and compound microscopes are two different types of light microscopes. Both are widely used in research in industry and also for hobby use and in education.

Both types of microscopes share some similarities but there are also important differences. They are similar because both are made of several lenses that are put together. They both have an objective and eyepieces (oculars) and they magnify much more than simple magnifying glasses.

I have seen some people refer to compound microscopes also as “normal microscopes” or “biological microscopes”. Neither of these two terms are appropriate. Stereo microscopes are just as “normal”, and they are also used in biological research.

There are some important differences as well. Stereo microscopes allow you to observe larger objects and it is not necessary to prepare them and to put them on a microscopes slide. The objects also do not have to be transparent. When you look at the object, then you will get a strong 3D (stereoscopic) view. The object will appear to almost “jump” into your eyes. Especially insects and other small animals are very impressive to look at this way.

There is one important point that is often a source of confusion. Some compound microscopes have a binocular head with two eyepieces. These microscopes should not be confused with stereo microscopes, which also have two eyepieces. Compound microscopes are not capable of delivering a stereoscopic (3D) image, even if they have a binocular head.

Compound microscopes have other advantages. They allow you to see much smaller objects. Microscopic water life and single-celled microorganisms can be seen much better with them. If you want to see individual cells then you need a compound microscope.

You can see that every microscope has its own world to explore. You can not say that one microscope is “better” than the other. For this reason, many people who do amateur microscopy will have both of these microscopes. Each microscope type has its own advantages and disadvantages, and the choice depends much on what you want to observe. People who are interested in observing whole insects or plants may most likely chose a stereo microscope, while those who are interested in viewing the much smaller individual cells should go for a compound microscope.

Let’s now look at the different kinds of microscopes in more detail. You can also watch a video where I explain the differences:

 

Stereo microscopes

Stereo microscopes are also sometimes referred to as dissecting microscopes because they are also used during dissection of plans and animals. Stereo microscopes are also often used by people who are doing electronic repairs, where some parts are so small that they are difficult to see otherwise.

If you want to look at large objects, such as whole insects, flowers of a plant or rocks and minerals, then a stereo microscope is better suited. You can put these objects directly on the stage of the microscope and start observing.

Stereo microscopes are suitable for objects that are opaque. These objects do not allow light to go through. Stereo microscopes have light coming from above (some also from below) and allow you to observe the surface texture of objects. Stereo microscopes therefore allow you to look at pretty much anything that will fit on the stage and there is no need to prepare the object so that it fits on a microscope slide. Coins, whole insects, your skin, clothing, and other textiles – almost all objects that you can place on the stage of the microscope can be observed. If you like to collect postage stamps or rocks and minerals, all these things can be directly observed with a stereo microscope.

A stereo microscope does not only give you a stereoscopic (3D) image, but also an image that is upright. This is made possible, because there are prisms built in into the microscope that make sure that the image is upright. In this way, a stereo microscope is almost like a natural extension of your normal vision.

There is also a large distance between the object that you want to look at and the objective of the microscope. This makes it very easy to manipulate the object. This is the reason why people who repair small objects (like watches or electronics) use stereo microscopes.

Stereo microscopes magnify between 10x and about 100x, but the highest recommended magnification is about 40x (otherwise the image becomes very dark and the depth of field is low).

When to buy stereo microscopes

• If you buy microscopes for young children, stereo microscopes are much to be preferred. They are less delicate, give an upright image and objects can be looked at without much preparation. There is also less parental supervision needed, because they are easier to operate.
• If you already have a hobby that could benefit from stereo microscopes: Collectors of stamps, coins, minerals and insects will benefit from stereo microscopes, as they allow you to observe these objects directly without any preparation.
• If you do not want to or can not prepare specimens: Objects viewed using stereo microscopes do not have to be mounted on slides (even though this is possible). Slide mounting does require a little bit of laboratory technique. If you are not interested in this, then buy stereo microscopes.
• If the objects are quite large: large objects (which can not be cut into sections) can only be observed using stereo microscopes.
• Choose stereo microscopes if you do not need large magnifications, but would like to view at objects stereoscopically (3D view).
• If you are interested in quick, uncomplicated exploration of the environment, without sample preparation.

Compound microscopes

Compound microscopes have the advantage that they allow you to magnify an object to a much greater extent (up to 1000x) compared to a stereo microscopes. In order to view these objects under the compound microscope, the object must be placed on a glass microscope slide. The specimen must therefore be sufficiently thin, small and transparent. If it is not, then it must be prepared and brought into this shape. It might be necessary to cut the specimen into very thin sections before mounting. It is not possible, for example, to take a large insect like a house-fly and observe it under the compound microscope as a whole. You will only see a dark shadow without many details. In order to view these objects under the compound microscope, you must first process them by either cutting them into thin sections (called microtoming). People who are not interested in preparing specimens this way can buy commercial microscope slides.

There are many specimens do not require much preparation, however. This includes water samples, insect wings, plant pollen etc. which can be quickly mounted on a slide without much effort. This is the reason, why many hobby microscopists like to look at water samples. There are countless moving microorganisms to look at and preparing a slide only takes a few seconds: put a drop of water and algae on a slide and put a cover glass on top.

One thing that some beginning microscopists find difficult is that the image that compound microscopes produce can be quite abstract at times. The objects are magnified so much, that they do not look like the original object anymore. Some people have difficulty of making sense of what they see and therefore you need to read up on Biology a little bit. A grasshopper under a compound microscope will show the individual muscle cells, but it will not look like a grasshopper anymore.

When to buy compound microscopes:

• Older children probably prefer compound microscopes, as they give them more possibilities to explore the unseen.
• If you want to see cells, then you must use compound microscopes.
• Choose compound microscopes also if you are interested in learning specimen preparation and basic laboratory work.
• Some people like to collect slides. If your interests are in making and collecting specimen slides, then compound microscopes are also better suited.
• If you want to learn new skills, then compound microscopes are probably better, because they are not as easy to use as stereo microscopes.
• Many resources that you find online are about compound microscopes. You might need more resources, because they are – as I already said – not as easy to use as stereo microscopes.

What to do if you can not decide which type of microscope to buy

If you can not decide which one to buy, then I suggest – buy both! Each microscope has its own world to explore. But maybe this answer does not satisfy you. Unless you have certain observation interests, I would suggest that you buy a compound microscope, because there is more to learn there. A compound microscope will keep you more busy, as there are slides to prepare, water samples to collect, and more “wheels to turn” on the microscope. Most hobbyists will have compound microscopes and it is therefore easier to share information and resources with them.

If you want to get a taste of a stereo microscope, but do not want to buy one, then you can experiment with cheap USB microscopes that can be plugged in into your computer. They do not provide a stereoscopic view, but the image produced is otherwise the same. You have light coming from the top and the surface structure of the object can be seen.