While there is a broad range of pricing for prime lenses, they can be less expensive than zoom lenses of comparable quality, especially at wider apertures. This cost-effectiveness stems from the more straightforward construction and fewer materials required.

Focaldistance vsfocallength

With ten years under my belt as a professional photographer, I've found that telephotos are better than wide for my work — here's why.

We mentioned the need to minimize footprint. So, how do we make a small sensor that can still measure high powers without overheating? The trick is to use a sensor designed for lower powers so that it's small, and then expose the sensor to the high power beam only for a short time – short enough that the total absorbed heat is low, but long enough for the sensor to measure it. The truth is, though, that this would mean the exposure has to be really short – in fact, shorter than the response time for power measurement! Enter "Pulsed Power" mode. Here's the basic idea:

Prime lenses are usually more compact and lighter than zoom lenses, making them convenient for travel and long shooting sessions. Their smaller size and weight are due to the absence of the extra glass and mechanics needed for zooming.

Earlier we said that, although the focus in this article has been power measurement, "we will say a few words about beam profiling solutions toward the end". Okay then…

The differences between cropped (APS-C) and full-frame sensors are significant in digital photography, influencing various aspects of image quality, field of view, depth of field, and camera system size and cost.

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On the other hand, the smaller APS-C sensors come with a "crop factor" of about 1.5x to 1.6x, effectively increasing the focal length of lenses and providing extra "reach," which can be beneficial for telephoto photography such as sports or wildlife. Despite potentially higher noise levels in low light, APS-C cameras offer a more compact and affordable option for those seeking a balance between performance and portability. This makes them attractive to amateurs, enthusiasts, and even professionals who value a lighter system.

Focus distance

The most popular wide-angle zoom range is 16-35mm. Most kit or standard zoom lenses go down to 24mm or28mm. The widest lenses on the market are 10mm (rectilinear) and 8mm (fisheye).

Let’s break it down: Wide-angle lenses (under 35mm) are your go-to for capturing vast landscapes and bustling street scenes. They fit more into the frame, which is great for sweeping views and architectural photography. Meanwhile, telephoto lenses (over 70mm) excel in bringing distant subjects into sharp relief. They're ideal for zeroing in on distant details, perfect for sports or wildlife photography, and they add a dramatic flair by compressing space, making elements in the photo appear closer together.

Here we see a 100 kW beam from a fiber laser, with its power being measured by a 120K-W sensor. The beam first passes through a "BeamWatch" non-contact high-power beam profiler. This unique instrument is based on a physical property of light known as Rayleigh Scattering, where the highly-concentrated light around the laser's beam waist is scattered off air molecules in its vicinity and captured by the camera. This allows for an analysis of the laser's waist without coming into contact with the beam. The result is a beam analyzer with no water cooling required, no moving parts, and no upper limit in the power of the laser being analyzed. And, since it is a camera-based system, it provides data at video rates; this allows the user to see more time-based characteristics of their laser system.

Prime lenses are the unsung heroes of the photography world. Fixed in focal length, they don't have the zoom capabilities of their counterparts, but what they lack in flexibility, they make up for in quality. Because they contain fewer glass elements, prime lenses can capture images that are not only sharper but also more vibrant.

Lens compatibility is another consideration; full-frame lenses can be used on both sensor types, but APS-C lenses on full-frame bodies may result in vignetting. Finally, while full-frame cameras are more expensive, they are preferred for their superior image quality and flexibility in various shooting conditions. Conversely, due to the crop factor, APS-C cameras are favored for their affordability, compactness, and built-in telephoto advantage, making them a versatile choice for many photographers.

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Focallength formula

Long-focal length lenses range in the 100-600+ range and appear to bring far away objects close to the camera. Made swimmingly for the landscape photographers in mind, long lengths are perfect for wildlife, the bird on the backyard feeder, the child at the top of a water slide, or athletes on the other side of the football field. Lenses longer than 70mm focus on infinity after 100 feet. This infinity-focusing distance means a couple of different things.

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Wide-angle camera lenses are a fan-favorite among most lifestyle bloggers and everyday shooters; they’re perfect for capturing an entire scene and confined spaces if you want to show how the entire bedroom looks or the whole restaurant with the crowds of customers — the shorter focal length lens will be your best bet.

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The application of new, advanced technology in measurement devices, can help both designers and users of high-power laser systems to optimize and control their processes, so they can confidently accomplish their goals and achieve consistently good results.

The magic of a prime lens lies in its simplicity. The straightforward optical design enhances light transmission, allowing for incredibly clear and precise images. This can make a noticeable difference in your photography, especially when shooting in low light conditions. Moreover, with minimal distortion and chromatic aberration, your photos will have a professional sleekness that’s hard to achieve with a standard zoom lens.

Focal length might sound technical, but it's really your secret weapon in framing the perfect shot. It's measured in millimeters and determines not just the angle of view—how much of your scene is captured—but also how your images are magnified. As a beginner, understanding this can transform the way you approach photography.

A given process is designed to bring the beam to the needed power density in a precisely controlled location. Consider the following sketch:

Focallength

The two laser parameters that are most typically the critical ones in high power laser processes are power density and focus location (and shape). Additional parameters sometimes become important and need to be measured, including pulse energy, actual beam profile (which determines the "focus-ability" of the beam), beam position and size (less than a full profile), and others.

focallength中文

A lens focal length combines various elements that help to focus the light and minimize distortions. The location where all the light rays converge to form a sharp image is known as the optical center of the lens.

Power – at the sort of levels were talking about, from maybe a few hundred watts to tens of kilowatts – is normally measured using a thermal sensor. Absorbed light becomes heat, and the resulting heat flow is proportional to the beam's power and is measured. The output can be a numeric readout on the display screen of a handheld meter, or perhaps the sensor interfaces directly with software running on a host system…It all depends on the specific needs of a given application.

As we mentioned, a sensor needs to be able to withstand not only the total power it will face but also the power density. Some important ways to prevent damage:

Beam power and focal plane location inevitably drift with time and use – a result of aging of components, contamination of the focusing lens by process debris, misalignment of delivery optics, etc. When that happens, the space in which the power density is high enough to affect the material can then move or change shape:

Then there's the standard lens, around 50mm, often hailed as the "nifty fifty." It’s akin to the human eye in how it captures the world, making it incredibly versatile. It’s perfect for everyday shooting and portraits, blending background and foreground elements naturally. As a beginner, using a 50mm lens encourages you to physically move around, engaging more with your environment, which can lead to more thoughtful compositions.

The simplest way to find the focal length of a lens is to look at its specifications. Most lenses have the focal length marked directly on them. For prime lenses, it will be a single number (e.g., 50mm), while zoom lenses will show a range (e.g., 24-70mm).

Focal spot analysis is done using various types of beam profiling technologies. In this article we'll focus mainly on power measurement, but we will say a few words about beam profiling solutions toward the end.

Beyond the technical benefits, using a prime lens influences your creative process. Without the ability to zoom, you’re encouraged to physically move around your subject to compose the perfect shot. This often results in more thoughtful framing and a better connection with your subject. Whether you’re shooting portraits, street scenes, or landscapes, a prime lens can push you to explore new perspectives and enhance your compositional skills.

FOV tofocallength

Several standard Ophir meters offer "Pulsed Power" mode, meaning they "do the math" automatically; the user is prompted to enter the "pulse width", and the readout is in units of power. "Pulsed Power" mode enables the use of standard, small and inexpensive thermal sensors to measure powers as high as 10 kW - since total amount of heat to be dissipated by the sensor is actually low.

Additionally, the larger size of full-frame sensors allows for better low-light performance and less noise at high ISO settings, enhancing image quality in challenging lighting conditions.

Focallength camera

Since cavemen first figured out how to throw rocks and shoot arrows, our ability to precisely deliver power has come a long way. High-power laser beams, by delivering a lot of power into a small and precisely controlled space, now help us manufacture components that would have been difficult - if not impossible - using purely mechanical means. Automotive and aircraft manufacture, shipbuilding, and similar heavy-industry applications have been dramatically changed by the ever-advancing capabilities of laser technology.

The way to prevent this is to monitor the relevant parameters of the beam with an appropriate level of accuracy. That way, you can catch any drift before it becomes a problem, and deal with it proactively.

Processes requiring less dramatic power levels also benefit; a single high-power beam can be "shared" among multiple parallel processing stations – and because they all use what started as a single beam, there can be much better uniformity and process control across these multiple stations.

Focal length in photography refers to the distance between the lens and the image sensor when the lens is focused on infinity. It's typically measured in millimeters (mm) and is a key determinant of a lens's angle of view — the extent of the scene captured by the lens — and its magnification.

There are a number of important challenges that must be addressed when it comes to measuring high power beams. Some of the main ones:

focallength是什么

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We mentioned the 120K-W sensor earlier; this is the first commercial sensor (read: small size, fast response time) for measuring up to 120 kW. It's designed for fiber lasers used in such applications as industrial material processing, military directed-energy applications, and similar. It's very small, considering what it does - 50 cm deep x 50 cm diameter, with a 200 mm aperture. Because of the way it works, it's in a sense almost like a blackbody - less than 1% backscatter, minimizing safety hazards.

In short, they help photographic subjects appear closer than they are, achieving a beautiful compression for that desirable blurred background. There is a wide range of telephoto lenses on the market, including:

They typically have larger maximum apertures (e.g., f/1.4, f/1.8, f/2.8), allowing more light to reach the sensor. This makes them excellent for low-light situations and for achieving shallow depth-of-field effects where the subject is in sharp focus against a smoothly blurred background.

Of course the meter will need to "know" that the scatter shield has been added; there is a separate calibration factor ("Laser" or wavelength setting) for the "scatter shield in" condition.

Any 24mm and 16mm lens is an excellent option if you want something extra wide. Focal lengths below 16mm are considered ultra-wide angles.

Lastly, fisheye lens are a super fun addition to the camera bag if you’re into the widest view possible. Their angle of view is usually 180°, allowing you to see half of a full rotation and offering a distinctive, hemispherical lens distortion. They cram in as much information as possible; thus, they don’t produce straight lines. These are awesome for creative, experimental photography projects, especially within fashion portraits or skateboarding content.

Getting into the art of photography? Just upgraded to a new camera body and need to decide which lens to purchase? Finding the right lens for your needs depends entirely on the focal length. Are you shooting portraits, weddings, sports, or wildlife? Street? Food?

A wide-angle lens is often characterized by a focal length of 35mm or shorter, giving the photographer a wide field of view. The wider your field of view, the more of the scene you'll effortlessly capture in the frame. These lenses are ideal for many scenarios, and most photographers have at least one trusty wide-angle lens in their kit. If you’re a beginner photographer or want the first lens for a camera camera, it’s wise to go with a nifty 35mm lens focal length.

It's also worth mentioning that when using Fiber Adapters at these high powers, the adapters themselves also need to be cooled! Note that highest power sensor for which we have standard FO adapters is the 400 W FL400A-BB-50. The "regular" adapters are not rated for more than that. With high power lasers, the delivery fiber itself is water cooled, as must be the fiber connectors. Ophir offers several models of QBH water-cooled fiber optic adapters.

Ophir offers "Scatter Shields" as an optional accessory. They absorb some of the backscattered light, and reflect some of it back into the sensor's aperture, reducing backscatter by some 70%.

Notice the Alarm and Interlock module on the 16K-W-BB-55; this protects the sensor from overheating in case there is a failure of the water cooling system. Some sensors use a somewhat different design: the temperature rise of the cooling water, and the water's flow rate, are combined to enable measurement of the power. Some sensors using this method are shown below, including a large-format 6 kW sensor, and a unique sensor for measuring up to 120 kW:

Parameters that are not controlled can unexpectedly change what the process is doing and where it's doing it. That can make your process unpredictable; in the case of an industrial, commercial process - it can eat into the profits the process is supposed to be generating.

At powers above a few tens of watts, we usually add a fan to help remove heat from the sensor. Although Ophir offers 2 fan-cooled sensors rated for 1.1 kW, water cooling is the usual solution for sensors rated for more than a few hundred watts. Most "regular" thermopile type sensors use the water just to remove the heat; some examples are shown below:

"Exotic" applications such as military directed-energy weapons, once of real interest only to sci-fi authors, are now reaching maturity. Experts often mentioned the "magic number" of 100 kW, the power level needed to make such things practical. Thanks largely to advances in fiber lasers and their scalability, industrial materials-processing systems operating at 50 kW and even 75 kW are almost standard items now.

If the lens marking is unclear or you want more details, the lens manual or the manufacturer's website will provide specifications, including the focal length.

Remember that all focal lengths depend entirely on the photographer’s vision or personal preference. Like all art forms, there are no steadfast rules to abide by. This article is merely a guideline for the purpose of each focal length, including some technical differences between the various offerings you see today.

Generally, choosing a long focal length lens, like 70mm, 135mm, or 200mm, is wise to isolate textures and distant features to create dramatic backgrounds. Wide focal length lenses, like 16mm, 24mm, or 35mm, thrive when you want the entire scene in focus, like when shooting simple landscapes with long leading lines.

Ophir's Helios is a compact industrial laser power meter designed especially with factory automation in mind. It is based on the same "Pulsed Power" concept as above, except in this case even the pulse width measurement is automatic, using an integrated fast photodetector. It measures up to 12 kW using a short exposure and therefore no water cooling. There are models for Profinet and EtherNet/IP.