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Stereo microscopes have been in use for a little over a century, but it’s not uncommon for those who routinely use them not to know how they differ from other models. Why are stereo microscopes so special?

With two optical paths and eyepieces, stereo microscopes provide a three-dimensional view of the specimen. Like our eyes, the optical paths converge onto the sample, coming to the focus point from different angles, providing a sense of depth that makes stereo microscopes so beneficial for dissecting applications. They also have a long working distance which allows easy access to the sample with tools. For this reason, stereo microscopes are also referred to as dissecting microscopes.

Let’s take a more in-depth look at stereo microscopes, how they work, and in which applications they should be used.

Parts of a Stereo Microscope

Every component of the stereo microscope is important to its unique function. Its parts may vary depending on the configuration and use of the microscope, but an average classroom stereo microscope will have the following components:

• Eyepieces: The microscope’s eyepieces are also called ocular lenses and are the part the viewer looks through to examine the specimen. The eyepieces are normally set at 10x magnification, but some models can reach up to 75x magnification.
• Diopter setting: This microscope component helps prevent eye strain by making up for the differences between the image seen through the left and right eyes.
• Objective lens: Each eyepiece of the stereo microscope is connected to its own objective lens. The microscope’s magnification level can be determined by a single fixed objective, a rotating multiple lens turret, or a zoom.
• Stereo head: This component holds the two eyepieces. In one optical design (Greenough), the objective lenses and stereo head are housed together in a single body.  In the second major optical design (Common main objective or Galilean), the head mounts to the top of the optical zoom body.
• Focus knob: Stereo microscopes are commonly equipped with at least one focus knob. This knob is used to move the stereo head up and down to sharpen the image of the sample.
• Top lighting: Many microscopes only have one source of lighting, but the stereo microscope has a top and bottom light. The top light illuminates the object from above. Top lighting can be built into the microscope stand, or can be delivered by an external source either attached to the bottom of the microscope (like a ring light) or by fiber-optic bundles that direct light where the user needs it (refer to the feature image for this article).
• Bottom lighting: The bottom light of the microscope shines light through the stage and improves the visibility of translucent objects.
• Stage plate: The stage plate is the spot where the specimen is placed. It is directly underneath the objective lens. The plate is often reversible with one black side and one white side to contrast the specimen.
• Stage clips: These clips are designed to hold any slides in place on the stage.

How Does a Stereo Microscope Work?

The stereo microscope is an optical light microscope that uses the light reflected off the specimen to create a clear image of the objects’ individual details. It magnifies things at low power and is commonly used with solid or thick samples.

As the light reflects off the object, the viewer’s left and right eyes see different angles of the same sample, creating a three-dimensional image that is more informative for viewing detail and surface structure than a microscope with a single objective.

When Should a Stereo Microscope Be Used?

Because a stereo microscope allows the examination of three-dimensional specimens with its two separate optical paths and long working distance, it can be used in a variety of applications. For example, biologists and students can use these microscopes to perform dissections, while botanists use them to examine plants. They can also aid in repairing circuit boards and watches, cleaning and analyzing fossils, and dermatological examinations.

With additional microscope accessories, the stereo microscope can be configured to match a variety of applications. Boom stands, flex arms, track stands, and table mounts can improve the microscope’s ease of use, and microscope illuminators can enhance the specimen’s image and provide needed contrast.

Looking for Stereo Microscopes? Turn to ACCU-SCOPE

If you’re looking for high-quality stereo microscopes for your research, medical, or instructional purposes, trust ACCU-SCOPE to meet your needs. We have some of the best microscopes in the industry! If you need higher magnifications, we also offer compound microscopes. Contact us today to receive a quote.

Microscopes are wonderful educational tools because they offer students hands-on experiences that bring textbook concepts to life. Because these instruments are vital to a student’s comprehensive learning experience, it’s important to choose the right kind of microscope when outfitting a classroom. A microscope will need to magnify things well, but must also be robust enough to withstand years of use by hundreds of students. Below are four key factors to consider when buying an educational microscope.

Type of Microscope

When choosing a new microscope for the classroom or educational lab, it will be necessary to consider the type of microscope your students will need. What will they be reviewing in class?

If they are looking at larger samples, a stereo zoom microscope could be a good choice for your students. This microscope is often used for biology dissections and examining rocks, minerals, plants, bones, and more. With a stereo microscope, students can get a 3D image of the sample they are studying.

A compound microscope (a.k.a. upright microscope) can be used for samples that the naked eye cannot see because it offers a higher magnification. Samples are prepared and mounted onto microscope slides before being viewed under the lens. Students often look at prepared slides of blood cells, bacteria, tissue, and parasites to save time and complexity of making their own slides.

For live samples such as living cells or organisms, students use inverted microscopes. These microscopes allow them to observe the samples in Petri dishes and other culture vessels. Unlike a compound microscope, the objective lens is located beneath the stage – this offers greater flexibility to accommodate dishes of various sizes.

If you’re still unsure which microscope is suitable for your educational application, you can also look at the size, weight, durability, and ease of use of the microscope to narrow down your choices.

Size

The size of a student microscope is one of the essential features you’ll want to think about when buying a microscope. Most likely, students will be moving the microscopes from storage to their workspace and back every day. In this case, consider a model that is lightweight and compact enough to be transported and stored with ease.

Durability

Often, microscopes in educational environments are used by students having minimal experience with microscopes. For this reason you want to buy a microscope that can withstand bumps, movement, and bounces that are bound to occur. Look for safety features like fixed eyepieces, a locking pin for the observation head, and a focus lock that can help your students’ microscopes to last longer. Microscopes with metal bodies are generally more durable than lighter weight models with plastic features.

Optics

Ensure the microscopes you buy have high-quality optical components so students can visualize all the minor details of a sample. A microscope with a wide magnification range, such as zoom or multiple objectives, enables students to observe samples at multiple magnifications thereby providing context of the detailed structures to the larger specimen. Most newer microscopes offer LED illumination providing energy savings, long lamp life and crisp, even illumination.

Discover the Best Educational Microscope at ACCU-SCOPE

In any science class or student lab, microscopes are essential. With so many types of microscopes available, it can be challenging to narrow down the options while deciding which one to buy. Let the team at ACCU-SCOPE help you discover the best microscopes for your educational purposes. We offer a range of microscope types and accessories, including stereo microscopes, inverted microscopes, and microscope cameras. If you have any questions about our microscopes, reach out to us today!

The term microscope originates from the Greek words mikros meaning “small,” and skopein, meaning “to look.” The first recorded use of a microscope-like instrument dates back to the late 16th century. Yet, it wasn’t until the mid-17th century that significant advancement in magnification enabled Van Leeuwenhoek to observe what he called “animalcules” in samples. These “animalcules” were later renamed bacteria and found to be the cause of several diseases such as tuberculosis and the plague. Still, years would pass before viral agents could be successfully observed with microscopy due to past limitations in magnification.

During the latter part of the 19th century, Adolf Mayer speculated that an unknown and unseen infectious agent was causing mosaic disease in tobacco plants. Although he never physically viewed the virus, further experiments involving the filtration of plant particulate matter showed the presence of an undetermined pathogen. It would take decades for the tobacco mosaic virus to be identified in crystallized specimens leading to the additional discovery of over 900 viral variants that infect plant species.

Early Discoveries in Microscopy

In the mid-20th century, the development of the electron microscope enabled researchers to finally observe viruses. By utilizing accelerated electrons, scientists were able to see particles significantly smaller than any elements viewed through the optical microscopes of the time. Although the visual discovery of viral particles was a profound advancement in observational methods, the inability to see viruses work in real-time using an optical microscope would remain elusive until the end of the century.

During the 1980s, light-based observation of viruses was finally possible using highly sensitive microscopes. For the first time, researchers could see viral particles interact with one another and inside cellular membranes. The mechanics of an infection caused by a virus could now be viewed in real-time, enabling scientists to better understand mechanisms of viral infection and illness. The virus could no longer elude detection or the new treatments that would be discovered as a result.

Modern-Day Microscopy

Significant leaps in technological advancements continue in the field of microscopy today. With advances such as phase-contrast microscopy, which can be used to study the impact of viruses on living cells, to TIRF microscopy, which can increase the effectiveness of detection utilizing specialized dyes, the field of microscopy is continuing to open the doors of scientific discovery.

ACCU-SCOPE is a leading provider of microscopes and accessories to provide researchers with robust detection capabilities. The pursuit of knowledge through the scientific process combined with technological advancement paves the way for a brighter future. Through microscopy, we will all benefit from a better understanding of viruses and their impact on us and the environment. To learn more about our microscopes for clinical and research laboratories, please feel free to contact us today.

As technological forces merge automation and computation with current advancements in optics, the full potential of biological microscopy is coming into focus. Since the advent of phase contrast microscopy by Frits Zernike in 1934, the pursuit of greater illumination techniques has been a driving force behind the many revolutionary advances that have taken place in the field.

The challenge of illumination is ever-present in microscopy. For decades, scientists struggled to find optimal forms of contrast manipulation to better visualize complex details in samples, and to probe deeper into the understanding of life’s complexities. If it were not for the constant pursuit of new techniques and new technologies, the entire scientific and medical communities would still be struggling to find their way in the dark.

2D vs. 3D Imaging

Traditional microscopy typically involves looking at a slice of tissue, cells, or microorganisms sandwiched between two pieces of glass (microscope slide and cover glass). The specimen is so extremely thin — often just a few microns thick — that it seems practically 2-dimensional by our observation. We focus on the specimen, and moving it in X-Y across the stage is generally sufficient to complete our observation.  Information obtained from 2D microscopy in this manner is absolutely beneficial, is the most widely used observation method, and continues to advance scientific knowledge. Yet, cells, tissues, and cellular organisms are 3D entities, and 2D imaging has limitations when exploring the complex mechanisms behind life’s functions. 3D imaging allows scientists and experts to closely examine these processes within a cellular context.

Fluorescence microscopy has truly advanced the application of 3D microscopy for the study of biological processes.  Where 2D microscopy only considers “planar” specimens, fluorescence microscopy adds a third dimension in the form of focus. High-resolution optics and noise-limiting technologies allow the microscope to acquire very thin optical sections through even a single cell (it’s a much more difficult task with thick specimens, but a topic for another time). Stack these images together (referred to as a Z-stack) and a 3D reconstruction of the specimen can be achieved. With the ever-increasing availability of observable data, long-standing mysteries about cellular functions will continue to be solved.

The Transition to Simplified Mechanisms for Non-Expert Users

Recently, there has been a shift in the development of scientific tools so that they can be better utilized by non-expert users. Most microscopes can now be effectively used by individuals with little experience in microscopy. This is due in part to the fact that many scientists and medical professionals are often trained in specialized disciplines. As a result of the depth of specialized training, they generally receive minimal training in microscopy, don’t fully understand how microscopes work (e.g. optics and physics), and don’t know how to optimize the microscope for the best results.

With the advancement of technology, microscopes and many imaging systems (e.g. cameras and software) are now being designed for ease-of-use. The operation of a basic microscope hasn’t changed in over 100 years, but software with a logical interface and retrievable imaging parameters dramatically steepens the learning curve. Microscopes are designed for greater ergonomics, haptics, and visual references (e.g. match the setting on the condenser diaphragm to the Numerical Aperture written on the objective) to simplify operation. It is a careful balancing act between improving technology while retaining accessibility.

Continuing to Shed Light on the Smallest Discoveries

As innovation and discovery continue to advance the field of microscopy, ACCU-SCOPE is here to provide you with the tools to build a solid foundation for your work. We are consistently evaluating our product offerings and adjusting our inventory to feature the latest in microscopy technology. Contact ACCU-SCOPE for more information about cell culture microscopes, clinical microscopes, cameras and digital imaging solutions, and other products that are essential for biological studies.

Phase contrast microscopes utilize a special technique to enhance the contrast of an image. This technique was developed to produce high-contrast images of transparent or unstained specimens that could not be viewed well under brightfield illumination. Here, we take a look at some of the advantages offered by phase contrast microscopes for clinical settings and other fields that frequently work with living cells, microorganisms, and similar specimens.

Observe Living Cells

Before Dutch physicist Frits Zernike invented the phase contrast microscope in the 1930s, scientists were unable to clearly view living cells. Instead, the organisms were dried on a slide and stained in order produce contrast. However, this process takes time, kills the cell or organism, and can lead to a loss of structure and, therefore, detail. By being able to view an organism while still living, scientists can see how the organism behaves, offering further insight.

View Thin or Transparent Specimens

Specimens that are transparent or translucent, such as very thin slices of tissue, can be difficult to study using brightfield, as much of the detail remains hidden to observation. Phase contrast can make it easier to view and study the details of the internal structure of a cell or microorganism thanks to the increased contrast and minimal manipulation (e.g. fixing) of the specimen.

Can Be Combined with Other Observation Methods

To get the best possible image for their specimen or application, scientists sometimes need to experiment with different observation methods. Phase contrast can be easily combined with other methods of observation, such as fluorescence, to reveal additional detail that couldn’t be observed with just one method.

Applications of Phase Contrast Microscopes

Phase microscopes are not limited to clinical applications. Many different types of specimens can be easily viewed with a phase contrast microscope, including:

• Live microorganisms, such as bacteria, mold, protozoa, and erythrocytes
• Fibers
• Lithographic patterns
• Glass fragments
• Subcellular particles, such as nuclei and other organelles

Phase contrast produces a unique “halo” around the edges of particles. This hallmark of phase contrast microscopy is particularly useful to rapidly locate tiny specimens in the sample such as bacteria or debris.

Find Phase Contrast and Other Specialized Microscopes from ACCU-SCOPE

No matter your laboratory’s requirements, we can help you choose the right microscope that fits your needs and budget. ACCU-SCOPE offers microscopes for clinical settings and many other specialized applications. To learn more about our products, or for any other inquiries, please reach out to us online or by phone.

Gemologists rely on high-quality microscopes to do their work. Perhaps the most common usage of microscopes in gemology is to conduct an appraisal of a stone. The microscope needs not only to have enough power to be able to see flaws and inclusions in a stone, but also features that accommodate viewing gemstones of all shapes and sizes with ease.

ACCU-SCOPE has an assortment of high-quality binocular and trinocular microscopes for gemologists and jewelry makers that provide the clarity and accuracy demanded of the profession, all at an affordable price point. Here are some features gemologists should consider when shopping for a microscope:

Magnification Power

To see basic details on a stone, 10x power is generally sufficient. However for higher accuracy, many gemologists find that magnification of 40-45x is preferred for viewing the structures inside of a gemstone, including striae, fractures, inclusions, and other elements used to grade gemstones that cannot be seen with the unaided eye or even a loop.

Illumination

In gemology, the most common method for illuminating a gemstone is darkfield illumination, and most gemological microscopes will be equipped with a darkfield base. Patented by Robert Shipley Jr. in 1939, darkfield illumination showcases the gem against a black background. Inclusions and other flaws scatter the light, making them stand out as bright objects against the dark background. Dust and scratches may also scatter light causing them to stand out as well.  Some microscopes also allow the operator to use brightfield illumination, which is useful for examining specimens with different zones of color or to mask dust particles and scratches. Those that photograph gemstones will want both options so that they can represent their subject in the best way possible.

Accessories

Gemstones require special accessories so that they can be easily held and manipulated, observed, and photographed. Depending on your exact needs, you may also want accessories that can hold stones of various sizes as well as jewelry, such as rings. Having a stand that tilts and rotates also makes it easier to view. If you choose a microscope without a base to suit various purposes, you can also purchase a gemological stand.

Find the Right Microscope for You

ACCU-SCOPE has various gemological microscopes along with specialized microscopes for numerous other applications so that you can find the right tool for your needs and budget. Contact us to learn more about our microscopes, get a quote, or find an authorized retailer.

Believe it or not, people used film for taking pictures with microscopes – big, clunky cameras bolted to the microscopes, often with separate control units, and no way to preview the picture.  Just push the shutter release, cross your fingers and hope for the best – of course you wouldn’t know until you actually developed the film.  Fast forward a few decades and now cameras are ubiquitous – in our pockets, on our mobile phones and devices, even in our doorbells, all ready to capture the moment at a moment’s notice.  However, microscopy cameras are, indeed, different than that ubiquitous smart phone camera.  So why isn’t color imaging in microscopy as simple as a selfie?

Just as with cellphones, there are a wide variety of options for color cameras for microscopes. So how do you know which camera is best for you? Take a closer look at the technology.

Color technology

The most common technology to deliver a color image is a camera featuring a Bayer color mosaic filter (Fig. 1) – a red, green or blue filter on each pixel.  Note that with this most common filter arrangement, a given pixel only “sees” one color — this means that the resolution of a full-color image (in megapixels) is only 25% of the total megapixels available on that camera. A Bayer filter is the same technology used in most professional and consumer cameras, and the cameras in our mobile phones.  It is much more cost effective than 3-chip cameras (different sensor for red, green and blue) or cameras that use liquid filter-based color filters (take sequential images of red, green and blue, then overlay them).  Of course, your application may dictate which technology is most appropriate (i.e. speed, resolution, flexibility, simplicity).

CCD or CMOS?

These acronyms refer to the technology used in the camera sensor.  Traditionally, CCD sensors delivered better quality images (i.e. less noise), and CMOS were cheaper and faster.  Newer CMOS technologies have greatly improved the image quality, and they’re still king when it comes to speed.  Even more recently, sensor manufacturers are concentrating their focus on CMOS technology, and the availability of CCD sensors is declining.

The turtle and the hare

If you are only imaging fixed slides or dead/inanimate objects, then there’s no need for a lightning fast camera – the specimen isn’t going anywhere, literally.  So, go for the best quality image possible, regardless of how fast or slow the camera.  On the other hand, if you are imaging living systems (i.e. live microorganisms) or a specimen in motion, then a faster “shutter speed” translates into better snapshots in time.  For live image streaming, displaying in front of an audience, or video capture, higher speeds are also preferred or necessary (i.e. 30 frames per second or faster is recommended), otherwise the audience could get motion sick.

Cameras with HDMI output generally provide faster frame rates for live preview, and often save the images to an internal storage device.  USB-output cameras used to have slower frame rates than their HDMI siblings, but the newer USB 3.0 cameras can stream at well over 60fps. USB cameras save directly to a PC while offering greater control of camera settings for image acquisition through software.  The latest arrivals are WiFi-connected cameras that take advantage of our mobile devices and a camera app for image acquisition.  Thanks to the latest wireless technologies, their frame rates are usually somewhere between those of HDMI and USB-output cameras.

More is better, right?

As general consumers of imaging technologies (first point-and-shoot cameras, now smart phones), we’re tricked into thinking “more” megapixels translate into better images.  NOT TRUE, at least not for microscopy!  Given the same size of the sensor, more pixels (or the little light-sensing component of a camera sensor) means smaller pixels which, in turn, means less “volume” in the pixel to sense light, thus reducing sensitivity.  Also due to the design of the technologies, there is a little more space between pixels in a CMOS sensor than a CCD sensor, therefore CMOS pixels tend to be smaller than those on a CCD.

And when it comes to sensitivity for lower light applications, [pixel] size does matter.  As I alluded to above, smaller pixels are less sensitive than larger pixels.  So for situations where sensitivity is important (i.e. fluorescence, darkfield, phase contrast), larger pixels (and consequently lower megapixel cameras) are actually preferred.  There is also an ideal pixel size for each microscope magnification, and this is determined based on the resolution of the microscope (please refer to the article “What’s the Deal with Megapixels?”  Suffice it to say that the higher the magnification, the larger the ideal pixel dimensions and, consequently, the fewer the pixels that fit on the sensor.

So, which camera is best?  That’s for you to decide (and our technical applications people can help).  Review the software and, of course, the image quality.  Consider how you will use the images (still images or live viewing), and the camera’s connectivity (HDMI, USB or WiFi).  One last word of advice: take the camera for a test drive.

Thanks for reading!

We all agree that a clean windshield or clean glasses work better and are more pleasing to look through. Microscopes work better when the optics are clean, too.  Dust and smears reduce the resolution, generate artifacts, and generally degrade the image, sometimes to the point of making the microscope useless.  Below are a few basic guidelines we use to clean microscope optics.  For best results, follow these steps in increasing order and NEVER soak the optic in any solvent!

1. Use a puffer (Figure 1)
   • Remove surface dust by blowing air across it, and you only need a puffer or compressed air to do this.  This also avoids potential for scratching or smearing optical surfaces.

2. Use lens tissue
   • Lens tissue has no lint, and lint can cause scratches.  We avoid using Kimwipes, too, as they may be abrasive.  Gently wipe an optical surface in a circular pattern, beginning in the center and spiraling outward (Figure 2).  Repeat. FYI, facial tissue contains a wetting agent that may add smears to the glass surface.

3. Use water or warm breath
   • In combination with Step 2, a warm breath may be sufficient to remove the dust, debris, and some smears.  You may also wet the lens tissue slightly before wiping.  We will also wrap the lens tissue around a cotton-tipped applicator stick or Q-tip.  Alternatively, you can fold the lens tissue into a point (Figure 4a; courtesy of https://micro.magnet.fsu.edu).

1. Use alcohol or lens cleaner (WEAR NITRILE GLOVES)
   • Alcohol or lens cleaning solution (Figure 3) is the next solvent after water/breath.  One of our favorites is Sparkle glass cleaner, but dilute this 1:1 with distilled or deionized water (a.k.a. Milli-Q water).  70% isopropanol or 70% ethanol is also acceptable, but not denatured alcohol.  Be careful when cleaning the eyepieces as these solvents may damage the rubber eyeshields.  Wrap lens tissue over applicator stick or Q-tip as above, and slightly dampen with solvent before wiping.  Work in circular/spiral motion from the center outward.  Repeat.

5. Use stronger solvents (WEAR APPROPRIATE GLOVES), or seek professional help
   • In some cases, and with some stuck-on substances like dried-on immersion oil, you may need to use other solvents such as xylol or a 1:1 mixture of ether-ethanol.  IMPOTRANT! DO NOT SOAK THE OBJECTIVE IN THE SOLVENT as this may soften the cement securing the lens elements.  Other organic solvents may also be used for more stubborn crud (Residual Oil Remover, pure petroleum ether, etc.).  Follow same procedure as in Step 4, and use sparingly!

One final tip.  It is easier to inspect and clean objectives if they are removed from the microscope.  Remove one of the eyepieces and look through it the “wrong way” (e.g. from the back; Figure 4b) at the lens – – it’s a handy 10x magnifier!  With a few seconds of practice, you can see smears, dust and even damage to the lens.

Enjoy your clean microscope and, to maintain peak performance, remember to clean those optics on a regular basis.

We are often asked to recommend the objectives for a microscope.  The objective sits closest to the specimen, and is an integral component of the microscope and crucial to delivering an acceptable image of the specimen.  All the information you need to know is written right on the barrel of the objective: flatness correction, magnification, Numerical Aperture, immersion medium, optical path design, and whether to use with or without a coverglass.  One of the more confusing criteria, however, is Numerical Aperture.  In this brief article, I’ll attempt to demystify Numerical Aperture, and how to get the most out of it.

Very simplistically, Numerical Aperture (“NA”) is the ability of an objective lens to collect light, and it’s written on the objective just after the magnification (Figure 1).  A higher angle of light = a higher NA (see Figure 2).  Additional light means more information, which means better resolution.  So the higher the NA, the better the optical resolution.  But it’s not as easy as moving closer to the specimen.

In order to take maximum advantage of the objective’s NA, the condenser should be adjusted to match – this adjustment is one step of Köhler Alignment.  Thankfully most condensers have an aperture adjustment for this purpose (see Figure. 3).  Since the NA changes every time you change objectives on a microscope (objectives with higher magnification typically have higher NA), the condenser should also be adjusted – this is literally a 2 second adjustment, and can make a HUGE difference in the image and resolution.  We’ll review Köhler Alignment in another article.

Let’s say that two objectives have the same magnification but different NAs. The one with higher NA will typically cost more.  And to get an NA of 1.0 or higher, you’ll need an immersion objective that requires some other medium than air (typically oil, water, glycerin, or silicon oil) to be placed between the objective and the coverglass above the specimen.  This additional medium bends (“refracts”) more light (therefore, more information) into the objective lens, thereby increasing resolution. Note that immersion objectives are specifically designed for particular immersion media, and no objective should be used with an immersion medium for which it was not intended – – this will void any warranty, and you won’t get the results you hoped for.

Numerical Aperture = n sin θ

where n is the refractive index of the medium between the objective and the coverglass, and θ  is the ½ angle of light collected by the objective lens (refer to Fig. 2).  Air has a refractive index of approximately 1.0 and typical immersion oil has a refractive index of 1.51.  You can see how oil is needed for an NA > 1.0.  Therefore in order to have an NA greater than 1.0, you’ll need to use an immersion medium with a refractive index higher than 1.0.

Objectives of the same magnification but different NAs will give different results.  A higher NA objective, when the microscope is properly adjusted, will have higher resolution and deliver a crisper image.  The trade off is that the depth of focus becomes shallower as resolution increases.  So if you want to have more of the specimen in focus, you may want to choose an objective with lower NA.

Finally, higher NA doesn’t necessarily translate into a better image.  Other optical qualities must be considered (e.g. correction for field curvature, chromatic aberration, spherical aberration, etc.), all topics for another time.

Thanks for reading!