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How to Buy the Right Microscope

Intro» Construction» Optics» Light» Focus» Components» Used» Conclusion

Chapter 3. Microscope Lighting

Unless your objective is to do outdoor fieldwork, I'd advise that you stick with a scope with a good electric lighting system.

The days of struggling to collect light with a sub-stage mirror are happily gone. Having an electric light on your scope is so much more convenient, and the added expense is well worth it.

Light is light, right? Well, not exactly.

There are major differences in lighting systems on scopes today. You'll find one of four different types of lighting systems on most student microscopes.

Tungsten Microscope BulbTungsten

The tungsten light (also known as "incandescent light") is perhaps the least expensive type of microscope bulb available today. Your home is filled with incandescent lights. They glow with light when an electrical charge is put through their tungsten filaments.

A tungsten bulb provides an inexpensive, steady source of light - but it is does have some disadvantages.

The light it produces is yellowish, which can affect the color accuracy of the specimen being viewed. This is not a big deal with a student scope.

One significant disadvantage however, is that the tungsten bulb generates quite a bit of heat, about 350 degrees worth! This heat can dry out specimens and kill live creatures such as protozoans swimming in a drop of pond water.

Another disadvantage is that during the time when these bulbs were so popular, there was no "standard bulb". As a result, there are hundreds of different types of tungsten bulbs which were used (and are still used) in microscopes, so finding your exact replacement can be difficult.

Tungsten lights are cheap to manufacture and install. Microscopes with tungsten lights are usually setup with an on/off switch and no dimmer, holding down expense.

Other lighting options need more equipment, and are more costly to produce, but, as I'll discuss next, you may agree with me that the nominal extra cost is worth it.

Fluorescent

Most of us have a fluorescent light here and there in our homes. These lights consist of a gas filled tube, which when electrified, comes alive with light.

A fluorescent light is more expensive to purchase, but is less expensive to operate.

There are several characteristics that make it an attractive choice in microscope lighting.

First, the light appears to the brain as a whiter light, more like the light we get from the sun. With this whiter light, objects look more like they really do in nature.

Another wonderful characteristic is that fluorescent bulbs give off very little heat. A fluorescent system operates at about 90° F. This can be very important when looking at the pond dwellers we mentioned above. I have viewed frolicking pond water creatures for as long as three hours with fluorescent illumination. This could not be done with tungsten light because of the heat generated.

I believe, for most hobby, student, and amateur use, that fluorescent light is the way to go. The coolness and sharpness it provides make it a prime choice.

By the way, if you are comparing brightness, a 7-watt fluorescent bulb produces about as much light as a 20-watt tungsten bulb, and a 5-watt fluorescent is about as bright as a 15-watt tungsten bulb.

LED

LED (Light Emitting Diode) is the latest technology, and it brings many advantages. LEDs consume very little power, the bulbs seem to last forever, and when setup with student microscopes, are frequently found paired with a rechargeable battery system making the scope cordless. They also have an advantage with the fluorescent - they provide a cool light.

While we saw LEDs make their first appearance on student microscopes, they are also becoming more and more popular on professional microscopes (like our I-4 where they are standard). Recent technology advances have made these bulbs brighter, much more reliable, and fully dimmable.

If you decide LED is for you, I would look for one that is dimmable. I've seen them TOO bright with only an on/off switch, making them almost painful to use.

If you want a student LED scope, give one with standard replaceable batteries (like AA NiMH) extra points over a "battery pack". When the AA NiMHs wear out (after 500 charges or so), you can just pop in some new ones from the local drugstore.

Another advantage that the LED cordless student scopes bring is that the microscope can be taken out and used without having to run a cord to plug them in. Very convenient!

Halogen

Halogen is seen primarily in medical and research scopes, and occasionally on student scopes. Halogen lamps provide a very white, bright, concentrated light, and are preferred on medical and lab instruments. Such scopes are usually fitted with a dimmer, which decreases the heat as well.

If you are purchasing a binocular (two eyepiece) microscope, halogen or LED is preferred because of its brightness.

One final "light" note:

When you buy a microscope, consider the problem this fellow had. His letter communicates a common problem.

-----Original Message-----

From: [Name removed]

To: GreatScopes

Subject: Microscope Parts

I have a [name removed] microscope. It's about 15 years old.

The lamp, my last one, burned out several weeks ago and no source I've spoken to seems to have any idea where I can get replacements. I'm hoping you either have access to the lamps I need or know of a source (U.S., hopefully) where I might obtain some.

Any assistance you can provide will be greatly appreciated.

Sincerely,

[Name removed]

-----End of Message-----

We did our best to help him, giving him a handful of possible suppliers, but he will have to work hard to find his bulb. We wished him well, and truly hope he succeeds...but he may not.

When buying a microscope, find out what you can about the bulbs it uses. The closer the bulb is to some sort of a standard (not just a microscope standard, but a "real world" standard), the better off you will be in 15 years. A good microscope could outlive the company that manufactured it. See if you can find out if a common standard was used for the bulb and base. If a common standard was employed, you'll be happier in the long run. You might consider asking the seller "Where else besides from you can I buy bulbs for this microscope?

The next chapter, Microscope Focus, will teach you about the two types of focus, and the importance of the focus gear ratio.


All of GreatScopes' lighted student scopes have fluorescent lighting systems, and most offer an LED upgrade. Our professional scopes feature halogen lighting or LED. You'll also want to know that our Student Series, 3088 Premium, and Achievers use a common fluorescent bulb easy to find many larger home improvement centers (Home Depot, Lowe's, etc.). The Professional scopes use the common two prong Philips halogen lamp you'll find there too.

Go to the next Chapter: MICROSCOPE FOCUS

Intro» Construction» Optics» Light» Focus» Components» Used» Conclusion

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