A lens focal length that’s greater than 50mm is considered a long focal length. This view is narrower than the normal view we’re accustomed to when paying bare attention. An image taken with a 100mm telephoto lens will have a much smaller section of coverage than a normal or wide-angle field of view.

Apart from the definition of focal length in photography as the measurement in millimeters from the lens to the image sensor, focal length has a direct impact on the angle of view, which is a static property of the lens in question but is impacted by the sensor crop factor.

Fixed lens camera focal lengths can also be multiplied by the crop factor of the sensor in order to compare it across formats. This is generally only important if you’re trying to replicate a look across focal lengths; i.e. you know you want a 135mm full-frame portrait style.

In order to figure out what working distance you will need to set your digital microscope to, you will need to refer to the viewing chart found on the microscope model’s product page and decide which working distance works best for you (especially if you have a WD restriction) in relation to your desired field of view.For instance, an end user who intends to use the digital microscope to assist with their electronics assembly and repairs on a PCB component may need to have at least 4-6” clearance under the scope to accommodate for their hand tools while working on a 1” area. They can consider going with the HD807 or HD801 low magnification digital microscope systems, both of which are popular options for PCB assembly and repair because they have long working distances (up to 16” and 12”, respectively) while being able to accommodate for the 1” FOV needed.

What happens if your application requires a long working distance while maintaining a small field of view? Say, for instance, you would like 5.3” minimum WD range on the HD807, but would like to have 0.09” smallest FOV instead. On our digital microscopes, there is usually a 1x rear coupler (sometimes 0.5x if specified) installed as standard to the back of microscope, between lens body and camera. The working distance is determined by the lens installed to the front of the microscope, so in order to maintain the working distance of the front lens, we would change out the rear coupler instead. In this case, installing a 2x rear coupler to the HD807 system would halve the FOV size range (doubling magnification) while maintaining the 5.3” WD (as seen in the on the “HD807h” column).

While it is more straightforward to choose an existing model that accommodates for all your needs, sometimes that might not be possible without slight modifications. Swapping out front lenses adapters or rear couplers are different ways to achieve your desired field of view specifications while also meeting working distance needs. Contact us today for assistance in finding the right digital microscope model for your needs.

Focal length in photography comes up far more often than focal distance, which is an entirely different property of a lens. Focal distance is related to focal length but is not dependent on it.

Telephoto lenses are those beyond 50mm. These lenses are also physically longer than wide and normal lenses. The field of view is smaller but you gain significant reach.

Standard focal lengths range from 35mm to 50mm depending on the type of camera sensor. The field of view provided by standard focal lengths approximates the field of view of the human eye.

Focal length and depth of field are different properties of both a lens and sensor but are somewhat related. Depth of field is how much of a scene is in sharp focus. How narrow or wide the depth of field is, is an interaction between focal length, sensor size, subject distance, and aperture value.

Focal length differences are especially stark with wide-angle lenses. Each mm of width makes a visible difference, unlike telephoto lenses where it takes several mm to be easily noticeable.

Focal length is one of the main considerations when buying and selecting a lens. And understanding how focal length works is essential to capturing the photos you want. Otherwise, you’ll be choosing lenses with random angles of view that only serve to confuse you with choices.

Most of our digital microscopes, however, are designed with one front lens that offers a fluid working distance range instead a fixed working distance. On our long working distance HD807 model, the system has a WD range of 5.3” to 16”. Imaging on this digital microscope can be brought into focus as long as the scope remains within this WD range. We provide specific working distances on the chart as a reference point to help you adjust accordingly to achieve optimal FOV range for your application. For instance, if you require a field of view of at least 3”, you will need to be at 8” WD or higher in order to get 3” FOV.

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Sometimes, the opposite may occur and you may have an application that has a working distance restriction. This is common for applications with structural limitations, such as requiring the microscope be set up within an enclosure or for observations of a specific component mounted on a larger part. Knowing whether you have minimum or maximum WD requirements helps us narrow down the digital microscope options best suited for your needs.

Hello Dan! I’m Mariam from Mauritius. I wanted to thank you for this deep explanation on focal length! I just bought my first camera and your article helped me so much!

In practical terms, angle of view and field of view are used interchangeably in photography to indicate the way our cameras “see” the scene, and using a short focal length or a long focal length will change drastically the field of view or the amount of the scene that is photographed.

Focal length is the physical measurement of distance between the lens and the imaging sensor when the subject is in focus.

In the relation between focal length and depth of field, when all other values are equal, short focal lengths (or wide angles of view) have deeper depth of field relative to long focal lengths (narrow fields of view). Thus, the longer the focal length, the farther the hyperfocal distance will be.

Hopefully, this article on explaining focal length has clarified some of the stickier aspects of the topic. Especially where they affect wide, normal, and telephoto fields of view.

Understanding focal length in photography can feel a bit overwhelming when trying to account for all of the ways it changes the properties of an image. Below, I’ve outlined the focal length differences across the major fields of view.

When you look at the focal length of the lens in question and you see a number below 35mm, you know you’re looking at a short focal length.

Please note that lens compression is not related to the lens, but to the distance from the subject (Ex. You can achieve the same field of view and perspective shooting an element with a short focal length like 20 mm or cropping the same area from a 50 mm as long as both images are taken from the same distance).

By taking the crop factor of a specific sensor and multiplying it by the field of view, we get the field of view as if it were viewed in the 35mm standard.

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By twisting the barrel of a zoom lens, you can adjust the focal length and field of view of your lens, which affects depth of field, distortion, and all other aspects of your image.

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So what are the mm in lenses? The key is to understand that focal length is calculated by measuring the distance from the optical center of the lens to the image sensor, and this distance is measured in mm. The longer the focal length, the physically longer the lens will be. Lenses with a wider view will have a shorter focal length and are physically shorter by comparison.

I emphasize that we get the field of view because again, lens focal length is inherent to a lens. A 25mm Micro 4/3rds lens has a 50mm full-frame field of view. However, it remains a 24mm lens with the distortion properties of a 24mm lens; it’s not magically a 50mm lens.

Lens focal length is a surprisingly nuanced topic! A simple physical measurement leads to so many considerations that go into how an image is composed. From the angle of view to depth of field, no aspect of a photograph goes untouched.

Focal length also relates to field of view (also called angle of view) because changing the focal length changes the field of view – I’ll explain more about how the field of view and focal length of a lens interact with each other in greater detail below.

The angle of view in photography is the area of the scene that is captured by the camera sensor. This area is described in degrees of coverage in front of the camera.

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How focal length works is by describing each lens in terms of millimeters (lens mm). This description is a hard-physical reality of the lens in question, no matter the brand, format, or aperture.

Super telephoto lenses have very different focal lengths, ranging from 300mm and beyond. When considering focal length and field of view, crop factor is incredibly important because you can gain significant amounts of reach using a crop sensor like Micro 4/3rds.

While many of our digital microscopes have a fluid working distance range that provides a FOV range at any given WD point, some of our economic models will have a WD range but a fixed FOV size at each working distance. On these digital microscopes, the WD needs to be adjusted in order to reach to a specific field of view size/magnification.This is the case with our economy auto focus model HDAF100 (viewing chart seen below). If your application requires minimum 0.5” field of view, you will need to be around 3” WD or higher to achieve 0.5″ FOV. If your application requires minimum 4.5” WD, then your smallest FOV size is 0.79”.

These lenses take on an expansive field of view that’s wider than what we normally pay attention to. An image taken with a 15mm lens will seem abnormally expansive, taking, for example, an entire landscape with ease.

Focal length determines many of the characteristics of the photos you can take as well as the physical dimensions of the lens.

Focal length = the distance from the subject to the lens + the distance from the lens to the camera sensor. You also need to understand if your lens is concave ...

The simplest focal length definition is a description of the distance between the center of a lens and the image sensor when the lens is focused at infinity.

Focal length comparisons are incomplete without the infamous crop factor discussion. Nowadays, we have APS-C, Micro 4/3rds, medium format, and full-frame, all of which use a lens focal length description centered around 35mm film gear. While this made sense when the digital revolution began, it’s often simply confusing to parse nowadays.

As we step into normal focal lengths, which are closer to our human vision (like 35mm), this effect is subtle to invisible. However, once we hit telephoto angles of view, the background appears to be closer to the subject. This effect increases as your lens mm does.

A prime lens can’t be adjusted and its focal length and field of view are fixed. The trade-off for flexibility in focal length is usually a wider aperture and better image quality because the prime lens can be optimized for its angle of view. Usually but not always; some top-quality zoom lenses nowadays are absolutely comparable to prime lenses in terms of quality for a given focal length.

It’s important to consider that focal length is a static property of a lens that’s true regardless of crop factor; for example, a 16mm APS-C lens is a 16mm lens even if it has a 24mm equivalent field of view in a full-frame camera. We’ll see + in-depth info about this below.

Not all digital microscopes are created the same: some will have fixed working distance requirements, while others have a fluid range to stay within in order to maintain image focus.On traditional microscopes with high powered objective lenses, there is a specified fixed working distance on each objective lens for the image to be in focus. In the same fashion, our high magnification digital microscopes have a fixed WD requirement, depending on the front adapter lens or objective lens installed. For instance, our HD806 manual focus high magnification model comes standard with a 1x front adapter lens installed, which needs to be at 3.4” WD (orange box in below image) to produce a focused image. If the front adapter is swapped out for the 2x front adapter lens instead (also included as a standard), then the WD will need to be adjusted to 1.5” (green box) to get the image into focus.

Normal or standard lenses have a focal length between 35mm and 50mm in full-frame terms. When comparing across formats, they have a field of view that’s also equivalent to a normal lens. These lenses best duplicate how we see the world.

Can you help me understand why a lens advertised as 60 mm f2.8 macro is described as 120mm and equivalent to 35mm focal length? I am completely bewildered.

When browsing for digital microscopes, you should take into consideration the working distance (WD) range on the system. For those unfamiliar with the term, working distance refers to the distance required between the front of the lenses to the top of the sample being viewed in order to bring the image into focus. Generally, the higher the magnification needed for inspection, the shorter the working distance required for observation to be in focus.

Wide-angle lenses or short focal lengths offer a great opportunity for shooting landscapes, cityscapes, Milky Way photography, and Northern Lights photography.

Standard lenses or medium focal lengths are suitable for shooting many different genres like portrait, street photography, landscape, etc.

Zoom lenses are what anyone who has ever picked up a camera in recent times is familiar with. In fact, they are so common that I often find non-photographers get baffled when I hand them a camera with a prime lens attached!

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Focal length touches upon many elements of the photography basics; composition, aperture, depth of field, and other aspects all shift when taking focal length into account! Each twist of the zoom ring or swap of a prime lens is a shift in the interplay of focal length and your creative vision.

The suggested ideal focal length where optical distortion is minimal is somewhere around 200mm but honestly is minimal from 50mm up. Image below left is a ...

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Hi Anne, it totally depends on the sensor size of the camera. For example, if you’re using a Micro 4/3 sensor camera with the 60mm f2.8 lens, since the crop factor is 2x, it means that you’re cropping the image the double, so technically it’s like shooting at 120mm focal length. Hope it’s clear. 🙂

Remember that if you tend to specialize in any type of photography, it’s crucial to understand how focal length affects your image so you can have a better idea of what sort of lenses you should be shopping with, as well as the impact they have on a subject and background. You can download my PDF photography guide to get more information about this.

Understanding your camera’s zoom ability helps you know what sort of pictures you can reasonably expect to take. Just like with an interchangeable lens camera (ILC), the camera will have a focal length range that tells you about the properties of the lens.

Focal length can feel a little abstract when looking at one lens versus another. One of the easiest ways to understand focal length is to look at images that use the lenses in question! To wrap up, here are some focal length examples for you to consider:

Photos taken with a long focal length look more “compressed” as compared to shorter focal lengths, and allow you to capture subjects from a farther distance without losing image quality.

While we do go into some depth here and there are some confusing elements surrounding the topic, I’m confident that by the end of this article, you’ll have a solid foundation on what is focal length and how it relates to digital photography.

Focal distance is the distance between the subject you are focusing to the camera sensor. Lenses that can work at close focal distances have higher magnification (or reproduction ratios) relative to lenses that need you to stay far from the subject.

As you can see, the focal length we choose affects the final image. Also, the field of view and lens distortions fundamentally affect the type of photography you do.

For example, if I use a short focal length in portrait photography, parts of the body that are closer to me can be unflatteringly emphasized. On the other hand, in genres like landscape photography, it’s more common to see images taken with a wide-angle view, not only to capture the entire scene in a single image but to emphasize elements in the foreground.

This concept can be complicated when the crop factor and the field of view come into play since we began to ask what is the equivalence of the focal length of a lens using it in a camera with a different sensor format.

Macro lenses have the highest magnification due to their unique construction, which reduces the focal distance they operate within and allow you to focus in very close subjects.

However, using a prime lens means that you have to physically move in order to create a given field of view. Which kind of lens is better is an age-old question and really comes down to your own personal preferences!

Photographs taken with short focal lengths show distortion in certain elements; those closer to the foreground are magnified whereas all the elements in the background will show a diminished perspective.

There are great apps and websites that allow you to calculate depth of field for a given focal length, aperture, subject distance, and sensor.

One key to understanding focal length is recognizing how the look of the image changes using lenses with different focal lengths. Using a wide-angle lens, foreground elements are emphasized while background elements are pushed even further away, looking smaller than they really are.

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Dino-Lite portable handheld USB digital microscopes, which we are authorized dealers for, are also designed in this manner. Dino-Lite products are a great option to consider if you have limited budget and/or require something with flexible observation capabilities rather than a traditional tabletop microscope configuration for inspection.

These super long focal lengths are usually more expensive but they allow to capture subjects from a very far distance like in sports and wildlife photography, and to shoot other genres like deep astrophotography.

Camera zoom lenses allows to change the angle of view without moving and are more versatile than prime lenses. The downside is that maximum apertures are not usually as fast as the fastest prime lenses. For example, an f/1.4 zoom would be ridiculously expensive and massive.