ISI & INRAugust 18, 2018
We start with the premise that choosing a microscope should be an enjoyable process!
That said, there are a number of variables that go into selecting a microscope system. The process can be a little daunting. Moreover, there is a bewildering range of quality – from cheap plastic microscopes to the most expensive German and Japanese brands.
This article, therefore, provides sensible advice to assist budding microscopists to make a more educated decision.
We recommend that you refer to the Glossary of Microscope Terms when reading this guide.
Before we start, you should know that everything in this article refers to light microscopes; that is a microscope that includes a built-in light source. There are other types of microscopes, such as electron or ultraviolet, but they are significantly more expensive and typically, used in commercial or scientific applications.
THE ‘RIGHT’ LIGHT MICROSCOPE
Microscopes are configured to suit different applications. It is important to ensure that you purchase a microscope that is well-suited to your application. There are three basic things you need to know:
First, a light microscope has two sources of magnification. The primary source is via the objective lens. The secondary source is via the eyepiece lens. Total magnification is achieved by multiplying the (magnification) power of the objective lens by that of the eyepiece lens.
For example: Standard eyepieces have a power of 10x. When using a 100x objective lens, the total magnification would be 1,000x.
Second, and perhaps most important of all, do not fall into the trap of being attracted by high levels of magnification. The vast majority of the world’s light microscope applications require magnification levels of less than 60x!
Third, you need to know whether you need a compound or stereo microscope..
COMPOUND OR STEREO MICROSCOPE?
Microscopes fall into two basic categories: Compound or Stereo, often referred to as high power or low power, respectively.
You will need a compound microscope if you are viewing “smaller” specimens such as blood samples, bacteria, pond scum, water organisms, etc. The reason is that such specimens require higher powers of magnification in order to see the detail. For this reason, a compound microscope is also known as a high power microscope. Typically, a compound microscope has 3-5 objective lenses that range from 4x-100x. Assuming 10x eyepieces and 100x objective, the total magnification would be 1,000 times. Compound microscopes are also integrated systems in the sense that the microscope body and base form an integrated unit.
When considering a compound microscope, you will also need to decide on whether you want a monocular, binocular or trinocular microscope. That is to say, a microscope with one, two eyepieces or one with two eyepieces and a third, trinocular port.
There are four basic variables in this decision:
1. Magnification: Monocular microscopes work efficiently for up to 1000X total magnification. For higher magnification levels, a binocular microscope is required.
2. Comfort: Most people find binocular microscopes more ergonomic and easier to use than monocular. Young children, on the other hand, find monocular easier to use.
3. Price: While the price ranges overlap, typically a monocular microscope is the least expensive type of microscope with trinocular being the most expensive.
4. Application: Most monocular microscopes do not include a mechanical stage, which is useful for more sophisticated applications. Most binocular microscopes do include a mechanical stage. A trinocular microscope is typically used when a third (trinocular) port is required for microphotography.
Now that you have decided on the type of microscope you need, there are several further variables to consider, most important of which is quality. Quality particularly applies to construction, lens and illumination. We will consider each of them.
a). Quality of construction
Most people believe that higher price equates to higher quality. This is partially true, but overly simplistic in the same way that it would be in referring to a car. As with a car, the finest light microscopes in the world tend to be extremely expensive. There are several well-known German and Japanese microscope brands that fall into this category. However, as with Ferrari cars, most people cannot afford them and do not need that level of refinement.
By the same token, there are a large number of low priced and low quality microscopes that range from plastic toys to cheaply made imports. Most of these are made of inferior quality materials, have minimal optical quality and are likely to break quickly. The vehicular equivalent might have been the Yugo! The danger of buying such microscopes is easily avoided by buying from a reputable microscope vendor.
In our opinion, there is now a healthy selection of fine quality microscopes that have excellent optics, but without the high price tags associated with well-known brands. In other words, like cars, many microscopes are now made that will achieve the same as the high-end brands, but without being “fully-loaded” or the brand cachet.
Implicit in such microscopes are design elements such as solid metal alloys, high quality prisms rather than mirrors and iris diaphragms not disk type diaphragms, among others.
b). Optical Quality
Optical quality is largely determined by the quality of the objective lenses and, to a secondary degree, by the quality of the eyepieces. The standard for good, quality objective lenses is an achromatic lens. An achromatic lens is one that corrects for the fact that different colors refract through a curved, glass lens at different angles. In “color correcting,” the microscope produces a significantly, enhanced, “flatter” specimen image of the specimen than would otherwise be obtained.
However, while achromatic objectives will satisfy most microscopists, some sophisticated users need a better quality objective that produces even flatter images of the specimen with less aberrations than achromatic lenses. These microscopists will require either semi-plan or plan objectives. Plan objectives, essentially, are “perfect lenses” and are usually required for sophisticated biological research…..and are double the price of achromatic objectives.
Finally, it is useful to ensure that the objectives are DIN compatible. While DIN (Deutsch Industrie Norm) is not a measure of quality, DIN objectives are useful since they are interchangeable from one DIN compatible microscope to another. Should you lose or damage an objective, you can easily replace it rather than have to buy a new microscope.
With regard to eyepieces, as a general rule, the wider the eyepieces the easier the viewing. Ask for Widefield (WF) or Super Wide Field (SWF) eyepieces. Be aware, however, that the width of the lens, itself will decrease relative to the size of the magnification power. In other words, higher power eyepieces have smaller eye ports.
There are four primary types of illumination: tungsten, fluorescent, halogen and LED.
In summary, a high quality, pedestal microscope should include halogen lighting as standard. Halogen produces a strong, white light and typically, include a variable rheostat so that the intensity of the light can be adjusted. All Omano, pedestal, microscopes use halogen light.
b). LED – Portable Microscopes
LED ring lights are increasingly common. When used with rechargeable batteries, the microscope becomes fully portable and can be used in the field or at conferences and trade shows with limited electrical outlets or where wiring is an issue.
c). Fluorescent Light
Fluorescent lighting is typically used in specialist, epi-fluorescent microscopes for biological research and similar applications. However, fluorescent ring lights are typically, used as additional light sources in stereo microscopes when more light is required. These ring lights should not be confused with fluorescent microscopes.
Basic illumination for entry-level microscopes.
a). Iris Diaphragm & Abbe Condenser
When buying a compound microscope, always ensure that the microscope has an iris diaphragm and good quality condenser – ideally, an Abbe condenser which allows for greater adjustments. Both items are found in the sub-stage of the microscope and are used in adjusting the base illumination. Most Omano compound microscopes include iris diaphragms and Abbe condensers, as standard.
b). Mechanical Stage
A mechanical stage is also useful for compound microscopes, particularly when viewing specimens at high magnifications. All our full-size, Omano compound microscopes include a mechanical stage with one exception where it is optional. A cost effective alternative is to purchase a mechanical slide holder.
SERVICE, SHIPPING & RETURNS
So far, we have summarized the basic variables that go into buying a microscope. Often overlooked is the quality of service that you will receive and the shipping and returns policy.
a). Knowledgeable Service
At Microscope.com, we believe that buying a microscope should be fun! It should not be daunting. More important, a good microscope vendor will have sufficient knowledge and patience to be able to walk you through the above, decision-making process. They will be able to guide you to a microscope that is well-suited to your application. We pride ourselves on this level of service. It is central to our success and is underpinned by a strong sense of traditional business ethics.
b). Returns Policy
That said, everyone makes mistakes! For this reason, we recommend that you only buy a microscope from a vendor with an adequate Returns policy. As this article indicates, there are many variables that go into buying a microscope. In some cases, however helpful the vendor is, the microscope may not quite work out as anticipated. Most reputable microscope vendors have a 14-30 day returns policy, during which time the microscope, (if in it’s original condition and packaging), can be returned for a full refund. At Microscope.com we have a 25-day Returns Policy. For more information read our Returns Policy
c). Shipping Costs
Finally, it is worth checking the vendor’s shipping policy. Shipping costs can add more than 10% to the cost of a microscope. At Microscope.com, we charge shipping at UPS cost. Keep an eye out for Seasonal Free Shipping!