Group velocity dispersion (GVD) is quantified by the second derivative of angular frequency with respect to wave number: \[ GVD = \frac{d^2\omega}{dk^2} \]

The effect is worse on cropped sensors. Therefore, if using a full-frame camera, you can typically use a smaller aperture than a cropped sensor without the risk of diffraction.

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As you increase the ISO on your camera, you introduce noise into the sensor. Therefore, high ISOs are a type of distortion.

This warping is more evident around the edges of our frame, on larger objects or ones closer to the camera. It also makes foreground objects larger and distant objects smaller.

The field of view (FOV) for a sensor system is the span over which a given scene is imaged. Although it may seem at first that the aperture size might determine ...

To fully understand wide-angle distortion, we first need to understand the concept of wide-angle itself. To do this, we also need to know about lens focal length.

The term “distortion” invokes a feeling of something bad in photography, and you could be forgiven for thinking it’s undesired.

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The other distorting effect is that the lower half of the building, which is closer to the camera, has been stretched wider and made larger in the frame, whereas the more distant object, the top of the tower, has been shrunk and looks much smaller.

Pincushion distortion is the opposite of barrel distortion. It causes straight lines to appear curved inward, creating a pinched or cushion-like effect. This type of distortion is often seen in telephoto lenses.

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Fisheye lenses produce extreme barrel distortion, resulting in a circular or hemispherical projection of the scene, like looking into a fishbowl. Therefore, this effect is intentional and used for creative or artistic images.

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For instance, in a phenomenon called anomalous dispersion, the group velocity can become greater than the phase velocity. The wave packet (group velocity) can move faster than the speed of light, while the individual waves (phase velocity) within it remain sub-luminal (slower than light).

Understanding GVD is crucial in wave propagation in systems like optical communication and laser technology, where wide frequency bandwidths are involved. It helps maintain signal integrity, predict and compensate for effects on pulse shape and duration, and improve imaging in resource exploration and ultrasonic imaging.

The standard field of view for a digital SLR, mirrorless, or 35mm SLR film camera is 50mm. This is equal to what we see with our eyes. Anything below 50mm = wide angle. Anything above 50mm = telephoto.

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Real estate photographers use wide angles to ensure the whole room is captured in the photo, but the wide angle also makes rooms appear much bigger.

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Group velocity is defined mathematically as the derivative of the wave's angular frequency with respect to its wave number: \[ v_{g} = \frac{d\omega}{dk} \]

In an optical zoom, the distance between the lens and the focal plane is known as the focal length, as illustrated here:

Delve into the fascinating world of waves physics with an in-depth exploration of Group Velocity. This comprehensive guide will shed light on the fundamental definitions and distinctive characteristics that set group velocity apart from phase velocity. Further, you're provided with detailed mathematical derivations, real-world examples, and illustrative case studies, helping you grasp the concept from every angle. From understanding the intricate formula to exploring its application in daily scenarios, you'll gain a robust understanding of Group Velocity and its profound role in physics.

You can use the wide angle effect to accentuate interesting foreground objects or scenery in a landscape, such as rocks, rivers or roads. The classic use would be to get down low in the middle of a road to make the start super wide and then have it taper off in the distance to some beautiful mountains.

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Aug 9, 2022 — It's when a line that is clearly straight, in reality, becomes curved when photographed with a flawed lens. Types of Lens Distortion. In this ...

Heading out to experiment with distortion photography? You may want to protect your camera and accessories through specialist insurance.

This causes them to spread out or interfere with each other, reducing image sharpness and producing a soft or blurry image.

Ever seen those photos of that big juicy hamburger, only to find that when you buy one and open the package, it’s a shrivelled piece of meat in a big bun?

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If you stand there looking with your eyes, there would be a similar effect, only not as pronounced. So, the wide-angle accentuates the distorted perspective.

However, while in many situations that may be true, in others, it is not. Distortion can also be used for creative effect. It can enhance or add drama to an image or scene.

Seismic waves provide a rich context for exploring group velocity. In the event of an earthquake, different types of seismic waves are produced, each with their own distinctive velocities. The group velocity here determines the pace at which the entire wave group advances, playing a crucial role in the speed at which the ground shakes. In fact, seismologists often use these wave speeds and differences to pinpoint the location and intensity of an earthquake!

Interesting, isn't it? But here's a key point: while the group velocity can exceed light speed, this doesn't violate Einstein's special theory of relativity because no information is transmitted at this high speed.

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Wide angles can also emphasise dramatic, stormy skies with interesting cloud formations. They are also great for reflections at sunset, where you can go wide and capture a great flaming sky reflected in a large body of water like a lake.

When you zoom in, you isolate a part of the scene and make it look artificially larger. But the other effect is that it can make objects seem much closer and bigger in relation to each other.

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In the case of wide angle, the distortion effect is warping or bending the perspective of objects in our scene. Wide angle stretches our field of view beyond what is considered normal and thus stretches objects within the composition.

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Lens diffraction is a type of distortion caused by small apertures. It affects image sharpness and detail, and it’s important to understand, especially when choosing aperture settings.

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Now, you could argue that every image we take in photography does just that. There is course, an element of truth to this.

Noise is more obvious in the darker areas of your scene, too. Noise can be reduced in post-processing, and there is also some great software out there, such as Topaz Denoise, that does an excellent job.

It can manifest as both lateral chromatic aberration (at the edges of the frame) and longitudinal chromatic aberration (in front of or behind the focal plane). This is easily corrected in post-processing.

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There are several types, so in this guide to lens distortion in photography, we will look at each one and learn when and how to avoid it or use it creatively.

The group velocity is a fundamental concept in understanding wave propagation, especially in media where the wavespeed is frequency-dependent. Mathematically, group velocity can be expressed as the derivative \( \frac{d\omega}{dk} \), indicating the rate of change of the angular frequency with respect to the wave number.

Key applications of the group velocity formula are seen in fibre-optic communications, laser physics, and seismology. It enables optimal data transmission, management of signal dispersion, production of quality light pulses, and efficient analysis of seismic waves, among other uses.

The image here was shot at 24mm focal length. The wide angle distorted the vertical lines by bending them inwards towards each other.

How bad this noise can be depends on the camera you use. Higher-end cameras perform better at high ISOs than cheaper ones. Also, camera manufacturers are making massive improvements in this area.

Every lens is different, but the rule of thumb for avoiding diffraction is to set a maximum aperture of F11 on a crop sensor and F16 on a full-frame.

Vignetting is darkening in the corners of an image. It can be caused by limitations in the lens design or when using filters or lens hoods that obstruct some of the light entering the lens.

The images below show the difference between using wide angle and telephoto on the same scene. The first was shot standing close to the grass with a 24mm focal length, while the second was shot from across the road using a 105mm focal length.

An example is the refraction of light through a prism. The phase velocity pertains to the speed at which individual light waves (of specific colours) travel, while the group velocity pertains to the speed at which the change in light intensity (caused by the superposition of light waves) travels.

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This type of distortion causes straight lines to appear curved outward as if they were wrapped around the surface of a barrel. It is most commonly associated with curvilinear wide-angle lenses and can make images look bulging in the centre.

When they do, it’s called a full-frame sensor (i.e., equal to 35mm film). Other sensors are smaller and commonly known as cropped sensors. These sensors have a crop factor, for example, 1.5x crop factor.

You can use this effect to accentuate features of a subject, add or create drama to a scene or make things look funny. Here are some uses:

Moreover, the phenomenon of signal distortion in radio and TV communications arises due to group velocity dispersion, where different frequencies in the signal travel at varying speeds, reaching the receiver at different times.

In the telephoto, the grass is a bit smaller, but more importantly, the church now looks bigger in the picture and closer to the grass.

Group Velocity Dispersion (GVD) is a wave phenomenon that refers to the broadening of wave packets due to the frequency dependence of the group velocity. This variation of group velocity with frequency results in frequency components of a wave moving at different speeds, causing the wave to disperse or spread out over time.

So, a cropped sensor’s equivalent standard field of view will be 50 / crop factor. So, for our 1.5x, it will be 50 / 1.5 = 33mm.

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When the aperture is set to a very small size, such as F22, light waves passing through it can be bent when they encounter an obstacle, like a small aperture.

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Sep 9, 2023 — Barrel and eyepiece: The precise construction and function of the microscope. KNOWLEDGE. In the complex world of microscopy, the barrel and the ...

The dictionary definition of distortion is—“The act of twisting or altering something out of its true, natural, or original state.”

As seen above, you can shoot from below to accentuate the height of a building or multiple buildings in a city to create a sense of drama.

The formula for calculating group velocity is \( v_g = \frac{d\omega}{dk} \), whereby \( \omega \) relates to the wave's frequency and \( k \) to the wavelength. This implies that the group velocity is the rate of change of the wave's frequency with respect to its wavelength.

Aside from injecting water into the burger to puff it up a bit, they also get right up close with a wide angle to make the meat look much bigger than it is.

In optical fibres used for internet transmission, light pulses can become dispersed due to variation in group velocity, diminishing the quality of data received. But intriguingly, changes in cable material or light wavelength can be used to manipulate the group velocity, establishing a more consistent signal and improving data transfer rates.

However, there are several distinctive features of distortion caused by the technical aspects of a lens. And these are what we will look at more specifically in this article.

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That said, you will lose sharpness and end up with a softer image. So be sure to only use a high ISO whenever there is no other choice.

You may have seen those classic images of a rabbit or a stag with a giant moon behind. This is not done using Photoshop but using a 1000mm focal length.

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If you wish to avoid or minimise this effect, you must move back and higher to shoot more straight at a higher perspective.