Objective Lenses: Compound microscopes have multiple objective lenses mounted on a rotating nosepiece, typically with magnifications ranging from 4x to 100x or higher. Other microscopes, such as dissecting or stereo microscopes, usually have fixed magnification lenses.

Illuminator: A steady light source (110 volts) used in place of a mirror. If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage.

Low powerobjective lens

this was my typical response whenever someone tried, for the umpteenth time, to explain depth of field to me.  I don’t think I’m particularly stupid but I just could not for the life of me get my head around what aperture to use for shallow depth of field, what deep depth of field looked like or what the heck focal length had to do with anything anyway.

This landscape photograph is a sweet little scene, with cows calmly grazing on the rolling hills at the foot of the mountain blanketed in cloud and so I wanted the viewer to be able to see everything in the image and by using deep depth of field the viewer’s eye is encouraged by my use of elements like colour, shapes and leading lines to travel all around the image.  Most of the image is acceptably sharp and every element is recognisable for what it is, trees, mountain, clouds and cows.

How doestheeyepiece compare tothe objective lens

This is the opening or hole in your camera’s lens.  Every camera lens has an adjustable opening that controls the amount of light coming through the lens, similar to the way the pupil in your eye works.  When we need more light to come through the lens we make the opening bigger, when less light is needed we make it smaller.

Condenser Lens: The purpose of the condenser lens is to focus the light onto the specimen. Condenser lenses are most useful at the highest powers (400x and above). Microscopes with in-stage condenser lenses render a sharper image than those with no lens (at 400x). If your microscope has a maximum power of 400x, you will get the maximum benefit by using a condenser lenses rated at 0.65 NA or greater. 0.65 NA condenser lenses may be mounted in the stage and work quite well. A big advantage to a stage mounted lens is that there is one less focusing item to deal with. If you go to 1000x then you should have a condenser lens with an N.A. of 1.25 or greater. All of our 1000x microscopes use 1.25 Abbe condenser lens systems. The Abbe condenser lens can be moved up and down. It is set very close to the slide at 1000x and moved further away at the lower powers.

Because you are all my peeps and I love you so, I did a little comparison experiment between the Canon 85mm lens and the 24mm lens, just to give you an idea of what we’ve been talking about.  For easy comparison, the exif metadata is posted below each set of images.

Whichlens isused inmicroscopeconvex or concave

3 types ofobjectivelenses

Depth of field describes how much of any given image is in focus from front to back.  For example, in the first image below, it’s really only the goose’s eye, part of it’s beak and head that’s in sharp focus, the rest of the image is out of focus.  We would say then that this image has shallow depth of field.

For the following 2 collages I used a smaller aperture of f/22 and it’s obvious that the depth of field (how much of the image is in focus) is deeper than in the previous 2 sets of photos.

Historians credit the invention of the compound microscope to the Dutch spectacle maker, Zacharias Janssen, around the year 1590 (more history here). The compound microscope uses lenses and light to enlarge the image and is also called an optical or light microscope (versus an electron microscope). The simplest optical microscope is the magnifying glass and is good to about ten times (10x) magnification.

Applications: Compound microscopes are commonly used in fields such as biology, medicine, and research, where detailed examination of small structures is required. Other microscopes, such as stereo microscopes, are utilized for examining larger objects or conducting dissections. Electron microscopes are used for high-resolution imaging of nanoscale structures.

If your appetite for photography has been well and truly whetted and you’re excited to learn more, now is the perfect time to take my online course.  It covers all the digital photography basics including learning how to photograph in manual mode and lots more.  I keep the classes small so that I’m able to give individual attention to each student’s work, the course is mentored personally by me from beginning to end and nobody is fobbed off onto a “teaching assistant”.  Personalised video feedback is given for all the image assignments and I’m available to assist and answer any photography related questions for the entire 5 weeks.

How to Focus Your Microscope: The proper way to focus a microscope is to start with the lowest power objective lens first and while looking from the side, crank the lens down as close to the specimen as possible without touching it. Now, look through the eyepiece lens and focus upward only until the image is sharp. If you can't get it in focus, repeat the process again. Once the image is sharp with the low power lens, you should be able to simply click in the next power lens and do minor adjustments with the focus knob. If your microscope has a fine focus adjustment, turning it a bit should be all that's necessary. Continue with subsequent objective lenses and fine focus each time.

Now that you know what depth of field is how the heck do you control or manipulate it?  Listen up photography peeps!  Aperture is not the only thing that affects depth of field and here’s the secret sauce recipe coming right up:

Diaphragm or Iris: Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide. There is no set rule regarding which setting to use for a particular power. Rather, the setting is a function of the transparency of the specimen, the degree of contrast you desire and the particular objective lens in use.

Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope. They almost always consist of 4x, 10x, 40x and 100x powers. When coupled with a 10x (most common) eyepiece lens, total magnification is 40x (4x times 10x), 100x , 400x and 1000x. To have good resolution at 1000x, you will need a relatively sophisticated microscope with an Abbe condenser. An Abbe condenser is composed of two lenses that control the light that passes through the specimen before entering the objective lens on the microscope. The shortest lens is the lowest power, the longest one is the lens with the greatest power. Lenses are color coded and if built to DIN standards are interchangeable between microscopes. "DIN" is an abbreviation of "Deutsche Industrial Normen". This is a German standard that has been adopted internationally as an optical standard used in most quality microscopes. A typical DIN standard microscope objective lens has a 0.7965" (20.1mm) diameter threads, 36 TPI (threads per inch), and a 55º Whitworth. Many high power objective lenses are retractable (i.e. 40XR). This means that if they hit a slide, the end of the lens will push in (spring loaded) thereby protecting the lens and the slide. All good quality microscopes have achromatic, parcentered, parfocal lenses.

Revolving Nosepiece or Turret: This is the part of the microscope that holds two or more objective lenses and can be rotated to easily change power.

It's important to note that the term "other microscope parts" is quite broad and can include various microscope types with different designs and features. The above differences are generalized and may not apply to every microscope outside the category of compound microscopes.

Wherearethe objectivelenses locatedon a microscope

Compound microscopes and other types of microscopes differ in their design and functionality. Here are the key differences between compound microscope parts and those of other microscopes:

The poor goose in the above image was sharing a very dark and dirty pigsty with two pigs, naturally I didn’t want any of the pigsty to show up in my photograph.  By using a shallow depth of field I was able to isolate my subject and keep the messy background blurred and out of focus.  This in turn encourages you, the viewer, to ignore the background and pay attention only to the subject of the image which in this case is the beautiful blue-eyed goose and that is exactly what I wanted to achieve.

For any experienced photographers who’ve happened to land on this page, this blog post is probably not for you, it’s a beginner photography post, not an in depth digital photography tutorial on all the in and outs of depth of field.  Merely what my friend Pete Frielinghaus would call, “‘n tong tippie”, a tiny taste on the tip of your tongue, just enough to whet your appetite.

Stage with Stage Clips: The flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage, you will be able to move the slide around by turning two knobs. One moves it left and right, the other moves it up and down.

Besides controlling how much light comes into the lens, the size of the aperture has a huge affect on depth of field and this my darlings is where a lot of the magic happens:

With the first 2 collages I intended to use the same aperture when comparing the lenses but only realised my error after the fact when I’d packed the tripod away and put my kitchen back into order, isn’t that always the flippin’ case?   I should’ve used an fstop of  f/2.8 on both but seriously folks, the aperture difference is minimal and doesn’t affect the experiment negatively, so don’t worry about it.

Objective lens microscopefunction

Magnification: Compound microscopes are designed for higher magnifications, typically used for observing microscopic details. Other microscopes may have lower magnification capabilities, suitable for larger specimens or samples.

There are of course also “normal” lenses that give an angle of view similar to the way we see things naturally with the human eye and they too produce very pleasing images.  There are of course endless nit-picking arguments about which lenses are considered “normal” but the consensus seems to be anything between a 35mm to 50mm focal length.  Don’t bother about all the arguments and in-fighting, decide for yourself what looks normal to you.

Understanding fstops and depth of field was one of the things I had the most trouble with as a fledgling photographer.  If this is ringing a bell for you and sounds familiar, don’t feel bad, it will all click into place eventually but let’s see if I can help get you a little closer to that mental click and aha! moment.

Shorter lens (wide angle) e.g. 24mm = Gives the illusion of more depth of field and appears to magnify the foreground and push the background further away.

With the landscape photograph below however, quite a lot of the image is in focus and therefore we would say that that image has deep depth of field.

That’s it peeps, I know it can be a bit much to take in all at once but if you read over the post a couple of times you should be able to hear the penny drop eventually.  Better still, take out your camera and do some test shots yourself, it’s the best way to learn.

High powerobjective microscopefunction

(b) Subject’s distance from the background – to blur the background we need to separate the subject from the background by at least 10 feet if not further.

Illumination: Compound microscopes often have built-in illumination systems, such as a substage light source, condenser, and diaphragm, to provide transmitted light through the specimen. Other microscopes, like dissecting or fluorescence microscopes, may utilize different lighting techniques or illumination configurations.

What arethe3objectivelenseson a microscope

1. Ocular eyepiece lens to look through. 2. Objective lens, closest to the object. Before purchasing or using a compound microscope, it is important to know the functions of each part. This information is presented below. Links will take you to additional information and images.

Sample Size and Depth of Field: Compound microscopes are designed to observe thin, transparent specimens placed on glass slides. They offer a narrow depth of field, allowing clear focus on one plane at a time. Other microscopes, like stereo or electron microscopes, can accommodate larger specimens or samples with more depth, providing a wider depth of field.

You make it sound so simple! Off to play with my camera and tape measure. Kicking myself that I signed up for an online course the day before I found your blog.

Ah, no worries Anne. I plan to publish an educational post once a month so between that and your online course you’ll be grand. If that doesn’t work, I’ll definitely be running this course again . Have a happy day and thanks for commenting 🙂

Longer lens (telephoto)e.g. 85mm = Gives the illusion of less depth of field and appears to compress or bring the background closer.

Rack Stop: This is an adjustment that determines how close the objective lens can get to the slide. It is set at the factory and keeps students from cranking the high power objective lens down into the slide and breaking things. You would only need to adjust this if you were using very thin slides and you weren't able to focus on the specimen at high power. (Tip: If you are using thin slides and can't focus, rather than adjust the rack stop, place a clear glass slide under the original slide to raise it a bit higher).

Eyepiece/Ocular: Compound microscopes commonly have a pair of eyepieces that provide binocular vision. Other microscopes may have a single eyepiece or sometimes no eyepieces at all.