When microscopy is new territory, buying a microscope can be a difficult task. Which type of microscope, how expensive, which brand, new or second-hand? These are all questions that I will try to answer in this section. It is important to realise that a lot can be examined and observed with a simple microscope. A beginner doesn't need an advanced laboratory microscope. That would be like buying an expensive sports car when you just got your driver's license. For most purposes, a decent educational or course microscope is more than sufficient. It is also good to know that the second-hand market is an interesting place to look for a microscope. On the second-hand market you will often find decent used microscopes of the better brands at very low prices. If you buy a new microscope, you actually pay more for less microscope, it's that simple. The quality of microscopes has not really improved over time.
Because there are many misunderstandings about microscopes, I have compiled a list of important points which can be used as a guideline when purchasing a microscope.
There are roughly 2 types of microscopes: 1: stereo microscopes and 2: biological microscopes, sometimes referred to as transmitted light microscopes. Stereo microscopes have two eyepieces so that you can see with both eyes and the image is 3-dimensional. Stereo microscopes are suitable for viewing larger objects such as small flowers, insects, minerals, crystals, micro-electronics, etc. The magnification of stereo microscopes is low, the maximum magnification is typically 20x-40x. A stereo microscope is more like a strong magnifying glass.
Biological microscopes are suitable for everything that is very small and here the individual cells and tissues of organisms become visible. These are microscopes with higher magnifications and they can be monocular (to be used with with only one eye), binocular (for both eyes) or trinocular (a binocular microscope with a photo tube). A common misunderstanding is that a microscope that can be used with both eyes is a stereo microscope. But a binocular biological microscope is something completely different. This section is about biological microscopes.
1) It's not about magnification. What matters is the resolving power of a microscope, which is determined by the quality of the objectives, not the magnification. Toy microscopes can magnify up to 1200x or more, but the images they produce are useless. They use cheap plastic lenses which makes it impossible to obtain a decent image. The high magnification is often used to convince people and in advertisements something like “can magnify up to 1600x!” may be written. Anything above 1000x magnification is nonsense, it is empty magnification at which no additional details are to be seen. Compare it with a photo that is enlarged; no extra details are visible, on the contrary, the image only gets worse.
2) A decent microscope has at least achromatic corrected objectives, coarse and fine focusing adjustment and a sturdy metal stand that is stable. Forget all plastic microscopes, but also all metal toy microscopes. In the past, toy microscopes were often made out of metal and sometimes these microscopes look a lot like a decent horseshoe microscope. But if you look at the sizes of these microscopes you will see that they are tiny. A genuine microscope is not tiny. Many of those toy microscopes are offered as 'student microscopes' but they have nothing in common with the real microscopes that are used in biology classes. Toy microscopes can be recognized by the fact that they are often presented in a box with a lot of unusable plastic junk (‘30-piece set’ etc). On the microscope itself there is often something written like '600x' or '1200x'. Usually you will see nothing at all with these microscopes at higher magnifications. They are only good for the trash bin.
3) The objectives of a microscope are the most important lenses as they determine the resolving power of the microscope. Typical objective magnifications are 4x, 10x, 40x and 100x. Decent objectives are corrected for chromatic aberrations and are at least achromatic. Furthermore, on a genuine objective, some specifications are written like for example 40/0.65 and often also 160/0.17. If an objective is only labeled with ‘40x’, it is usually of lesser or bad quality.
4) The eyepieces or oculars are the lenses which you look through and they magnify the image formed by the objective. Typical eyepiece magnifications are for example 5x, 10x and 15x. The total magnification obtained with a certain objective is the magnification of that objective multiplied by the magnification of the eyepiece, for example 40x10 = 400x.
5) Most of the time, you don't need more than 400x magnification. Many people have the wrong idea about magnification, they think that you have to use a magnification of 1000x or more. But 400x is already a lot. A higher magnification may only be required for very small organisms such as bacteria and fungi or some small single-celled organisms. However, most unicellular organisms can readily be seen with 200-400x magnification. If you are going to study plants, you will not need more than 40x-400x magnification.
6) With a monocular microscope, you can see as much as with a binocular microscope. However, it is more comfortable to look with both eyes instead of one. Binocular microscopes are usually more expensive than monocular microscopes. If you are only going to view the image via a camera on a monitor or laptop, then a monocular microscope is all you need. But the image you see directly through a microscope will always be sharper than what you see on a screen. This is because the image on a screen is further enlarged and the quality is also determined by the quality of the camera being used. Do not buy a so-called 'digital microscope' or USB microscope. Many people seem to be attracted to the word 'digital' and in advertisements they make use of that. Do realise that a microscope is by definition an optical instrument and the fact that you can digitise the image is only a side issue. This can be done with any microscope, also the very old ones, by using a special eyepiece camera, webcam, digital camera or just your smartphone.
7) Microscopes with an LCD screen or built-in camera, you better stay away from those. These digital microscopes seem to be popular, but they are junk microscopes and are nothing more than toy microscopes that allow you to see an image on a small, cheap low-resolution screen. What' s even worse is that they can be quite expensive. These microscopes have very poor optics and cheap electronics. Any electronic component ages very quickly because there is much development in this area. For example, analogue cameras have barely any value today, this in contrast to their lenses, which can still be used on modern digital cameras. Optical parts don't really age which is a major advantage of microscopes. Microscopes from a century ago can be combined with the newest digital photographic technology.
8) Older used microscopes are most of the time better than new microscopes if they were handled properly by the previous owner. New microscopes contain a lot more plastic parts that break easily and plastic parts are difficult to repair. Older (black or gray) microscopes are very solidly built, you will still regularly find them in laboratories, 50-60 years after they were manufactured. The optics have not changed much over the years, with 80 years old objectives you can still get nice images. The term 'obsolete' is therefore hardly applicable to microscopes. It is better to buy an older second-hand microscope from a well known brand (see point 9) than a new microscope from a lesser known brand.
9) When it comes to good quality microscopes, you will regularly come across these names on the used market in the Netherlands (eg Marktplaats): Zeiss, Olympus, Nikon, Leitz, Reichert, Wild, Asako, Meopta, Kyowa, Swift, American Optical / Spencer, Euromex, Luctor Baarn.
10) Buying a bad microscope will quickly lead to frustration and lack of interest. It does not motivate at all to look through a microscope that gives a blurry image. That is also the reason that many children who have ever been given a toy microscope never touch a microscope again in later life. We can thank the manufacturers of this junk for permanently ruining a fascinating hobby (and possibly later career choice) for a lot of people.