In Figure 5, a linear polarizer was placed in front of the lens in a machine vision system to remove obfuscating glare such that an electronic chip could be clearly seen. The left image (without polarizer) shows randomly polarized light scattering off of the many glass surfaces between the object and the camera sensor. Much of the chip is obscured by Fresnel reflection of the unpolarized light. The image on the right (with polarizer) shows the chip without glare obscuring any of the object details, allowing the chip to be viewed, analyzed, and measured without obstruction.

Unstressed clear objects between crossed polarizers should yield a completely dark field, however, when internal material stress is present, the localized changes in refractive index rotate the angle of polarization, resulting in transmission variations.

The lens aperture controls how much light enters the camera through the lens. It also affects the depth of field. Aperture settings are called f-stops. It might seem counterintuitive, but a high f-number means a smaller aperture opening with less light coming through, while a low f-number means a wider aperture and more light hitting the sensor.

All lenses are said to have at least some amount of chromatic aberration, but some have more than others. Fortunately, it is easily removed or reduced in post-processing in Lightroom and other editing programs.

Dichroic polarizers absorb a specific polarization of light, transmitting the rest; modern nanoparticle polarizers are dichroic polarizers.

When looking at the specs of a camera lens, you may have noticed that the manufacturer often shares the number of lens elements and the number of groups those elements are arranged in.

Unpolarized light can be considered a rapidly varying random combination of p- and s-polarized light. An ideal linear polarizer will only transmit one of the two linear polarizations, reducing the initial unpolarized intensity I0 by half,

Parfocal lenses are generally more expensive than varifocal lenses. Advantages of parfocal zoom lenses may also include an increased zoom range, smaller dimensions, and lower weight.

In order to select a specific polarization of light, polarizers are used. Polarizers can be broadly divided into reflective, dichroic, and birefringent polarizers. More detailed information on which type of polarizer is right for your application can be found in our Polarizer Selection Guide.

UV coatings: These coatings help to block ultraviolet (UV) light, which can cause color shifts in images and can be harmful to the human eye.

Lenses have either a focus-by-wire or linear focusing system. Focus-by-wire is an electronic focusing system while linear focusing is a mechanical system.

Anti-reflective coatings: These coatings help to reduce the amount of light that is reflected off the lens surface, which can help to reduce flare and ghosting in images.

Camera lens componentsexplained

Mustache distortion is a combination and barrel and pincushion distortion. Straight lines toward the center of the image bow outward away from the center, while those on the edges bow inward toward the center.

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Reflective polarizers transmit the desired polarization while reflecting the rest. Wire grid polarizers are a common example of this, consisting of many thin wires arranged parallel to each other. The light that is polarized along these wires is reflected, while light that is polarized perpendicular to these wires is transmitted. Other reflective polarizers use Brewster’s angle. Brewster’s angle is a specific angle of incidence under which only s-polarized light is reflected. The reflected beam is s-polarized and the transmitted beam becomes partially p-polarized.

DSLR vs. Mirrorless. There’s also a difference between DSLR and mirrorless lenses, and lenses made for APS-C and full-frame cameras. DSLR and mirrorless cameras also have different mounts, even when made by the same manufacturer, so make sure you’re buying the right lens. Canon and Nikon make adapters that allow you to use one of their DSLR lenses on one of their mirrorless cameras without a problem. There are also some third-party manufacturers that also make adapters. However, they don’t always work as well as in-house adapters.

If you expect to be doing a lot of photography indoors or in other low-light settings, you probably want a “fast” lens. This is a lens with a low f-stop setting such as f2.8, f2 or lower. Also, some zoom lenses have variable apertures. For example, a 100-400mm zoom might be f/4.5-5.6. This means that it will go down to f4.5 at its shortest focal length, but will only go to f5.6 as you zoom in and go to longer focal lengths.

Light is an electromagnetic wave, and the electric field of this wave oscillates perpendicularly to the direction of propagation. Light is called unpolarized if the direction of this electric field fluctuates randomly in time. Many common light sources such as sunlight, halogen lighting, LED spotlights, and incandescent bulbs produce unpolarized light. If the direction of the electric field of light is well defined, it is called polarized light. The most common source of polarized light is a laser.

Nikoncamera lens components

Everybody shakes. This can result in camera shake and blurry pictures for still photographers and jitter in video. This is especially true with long shutter speeds or with large and heavy telephoto lenses. Many lenses now come with some form of image stabilization, a system designed to compensate for shaking and help you get a sharp image. Image stabilization also lets you use a longer shutter speed so you can get sharp images in low-light situations.

Water- and oil-repellent coatings: These coatings help to prevent water and oil from adhering to the lens surface, which can make it easier to clean the lens and can help to improve image quality.

Another characteristic way to see how polarizers reduce reflective glare is by viewing water surfaces. In Figure 7, the surface of the water appears reflective in the left image, obscuring what is below the surface. On the right, however, the rocky debris on the floor of the body of water is much more clearly visible.

Glass lens elements may struggle with chromatic aberration, so manufacturers may include some low-dispersion elements created with other materials (e.g. fluorite) with lower refractive indexes in order to reduce those aberrations.

Using a parfocal lens allows you to zoom in to a subject for focusing but then zoom out again for creating your desired composition without worrying that your focus will be thrown off in the process.

Where θ is the angle between the incident linear polarization and the polarization axis. We see that for parallel axes, 100% transmission is achieved, while for 90° axes, also known as crossed polarizers, there is 0% transmission. In real-world applications the transmission never reaches exactly 0%, therefore, polarizers are characterized by an extinction ratio, which can be used to determine the actual transmission through two crossed polarizers.

Edmund Optics® offers a wide variety of polarizers, waveplates, polarizing beamsplitters, and other polarization-manipulating optics.

Lens manufacturers have added stabilization modes to improve performance in special situations. Most telephoto lenses come with a Mode 1 and a Mode 2. Mode one is general purpose and best for stationary subjects. Mode 2 is for panning – following subjects moving in a straight line such as a car or runner. Some lenses have a Mode 3. This is for photographing subjects that moving erratically such as athletes on the field or birds in flight.

We hope this beginner’s guide to lens features was helpful as you try to wrap your head around the difference between various lenses on the market.

Lens mounts. Most camera manufacturers have a proprietary lens mount, which means you can’t mix and match lenses from different camera manufacturers. Canon lenses won’t fit on Nikon or Sony cameras and vice versa.

There’s more to consider than focal length and price when buying a new lens. Lenses come with an assortment of features such as stabilization and weather sealing, plus issues like distortion and bokeh. Here is a guide to help you understand some of the topics and help you make the right choice in your next lens.

Despite the overwhelming presence of and preference for autofocus lenses, there are plenty of manual focus lenses available. These are mostly used in special situations such as night, macro, and landscape photography when super-precise focusing is required or autofocus may not work properly. Manual focus lenses are usually less expensive than autofocus lenses.

Lens coatings are thin layers of material that are applied to the surface of camera lenses to improve their performance. There are several types of lens coatings, each of which serves a specific purpose. Some common types of lens coatings include:

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The two orthogonal linear polarization states that are most important for reflection and transmission are referred to as p- and s-polarization. P-polarized (from the German parallel) light has an electric field polarized parallel to the plane of incidence, while s-polarized (from the German senkrecht) light is perpendicular to this plane.

Molecular compounds that have the same type and number of atoms, but different molecular arrangements are called stereoisomers. These stereoisomers are “optically active” and will rotate polarized light in different directions. The amount of rotation is determined by the nature and the concentration of the compound, allowing polarimetry to detect and quantify the concentration of these compounds. This is the premise for identifying which stereoisomer may be present in a sample, which is important because stereoisomers can have vastly different chemical effects. For example, the stereoisomer limonene is the chemical that gives oranges and lemons their characteristic scents.

Camera lensparts diagram

The angular difference between the axes of polarization of the two polarizers is directly related to the amount of overall light attenuation of the set of polarizers. By changing the angle offset, the optical density of the polarizer set can be varied, achieving a similar effect to using a neutral density filter. This ensures that the overall field is evenly illuminated.

Certain shapes may be used in other elements to improve image quality in other ways. For example, aspherical lens elements are often used to combat distortion in wide-angle lenses and to reduce spherical aberrations in fast lenses.

The same phenomenon can be seen in the Figure 6. In the left image (without polarizer), unpolarized light from the sun is interacting with the windows of the Edmund Optics building and most of this light is reflecting off the windows. In the right image, a polarizing filter has been applied such that the reflected light, rich in one polarization type, is being blocked from the camera sensor and the photographer, using the other polarization type, can see into the building more easily.

With a focus-by-wire system, when you adjust the focus ring you send a signal to adjust the optics and focus the lens. With a linear system, you actually adjust the optics when you turn the focusing ring.

APS-C vs. Full frame. Lenses made for full-frame cameras will work perfectly on APS-C cameras, but lenses made for APS-C won’t work on full-frame cameras because of the smaller field of view.

You’ll see this most often in astrophotography when stars along the outer edges of the image look more like comets than points of light. You can’t correct coma in post-processing, but you can reduce it by using a higher f-stop. However, you probably don’t want to use a high f-stop if you’re photographing the night sky. Look for a lens with little or no coma if you plan to shoot the stars.

About the author: John Tunney is a fine-art photographer and instructor living on Cape Cod in Massachusetts. You can find his work on his website and on Instagram.

Camera lens componentsdiagram

Figure 11 shows a photo taken of Edmund Optics Headquarters and the variation in the color of the sky, grass, and foliage from using or not using a polarizer in front of a camera lens. Because electrons in air molecules scatter light in many directions, the appearance of the sky without a polarizer is a lighter shade of blue, as seen in the left image (without polarizer). Additionally, the surface of leaves of trees and on blades of grass are very slightly reflective. Using a polarizer filters out some of the light reflected from these surfaces, darkening the perceived color of these surfaces.

Polarization control is also very important in the chemical, pharmaceutical, and food and beverage industries. Many important organic chemical compounds, such as active pharmaceutical ingredients or sugars, have multiple orientations. The study of molecules with multiple orientations is called stereochemistry.

The analyzer only transmits light that has experienced a specimen-induced phase shift and continues to block all the unaffected light from the source which was originally polarized by the polarizer. If the birefringence of the specimen is known, it can then be used to determine the specimen thickness. If the specimen thickness is known, it can be used to deduce the birefringence of the specimen. A convenient chart used for this purpose is known as the Michel-Levy interference color chart in Figure 14.

A lens with “bad” bokeh will show distinct edges around the circle of light and may even display “onion ring’ bokeh – a bright point of light will have rings within it, like the rings within an onion or tree.

Ring light guides are popular illumination sources due to their even, diffuse illumination. However, glare or reflection of the ring itself may occur. Polarizing the ring light output and the lens separately can reduce these effects, and bring out surface details as seen in Figure 9.

Camera lensparts and functions

Understanding and manipulating the polarization of light is crucial for many optical applications. Optical design frequently focuses on the wavelength and intensity of light, while neglecting its polarization. Polarization, however, is an important property of light that affects even those optical systems that do not explicitly measure it. The polarization of light affects the focus of laser beams, influences the cut-off wavelengths of filters, and can be important to prevent unwanted back reflections. It is essential for many metrology applications such as stress analysis in glass or plastic, pharmaceutical ingredient analysis, and biological microscopy. Different polarizations of light can also be absorbed to different degrees by materials, an essential property for LCD screens, 3D movies, and glare-reducing sunglasses.

In a simple polarization microscope system, a linear polarizer is placed in front of a microscope light source, below the specimen stage, to polarize the light entering the system. Another linear polarizer placed above the specimen stage is referred to as an “analyzer,” as this polarizer is rotated to achieve the desired effect when analyzing the sample and while the first polarizer is kept stationary. The analyzer is then rotated such that the polarization planes of the analyzer and polarizer are 90° apart. When this has been achieved, the microscope has a minimum transmission (crossed polarizers); the amount of light transmission will be proportional to the extinction ratio of the polarizer and analyzer.

There are a couple of exceptions. Leica, Sigma, and Panasonic created the L-mount alliance, which means their customers can mix and match lenses with their L-mount cameras. Olympus and Panasonic created the Micro Four-Thirds camera. Their customers can use lenses from either manufacturer.

Camera lenses have three types of optical distortion: barrel, pincushion, and mustache. An image with barrel distortion looks fine in the center but starts to curve toward the edges. Lines on opposite sides of the center appear to bow outward like the edges of a barrel. You’ll see this effect with wide-angle lenses.

Expenses lenses geared toward professionals typically exhibit less focus breathing than cheaper, lower-end lenses aimed at beginners.

Parts of alensPhysics

Pincushion distortion is the opposite. Lines away from the center start to bow inward toward the center. It’s an effect you’ll see with telephoto lenses.

Once the analyzer has been aligned perpendicularly to the polarizer, an anisotropic, or birefringent, the specimen is placed on the specimen stage. The specimen rotates the polarized light a designated amount, proportional to the specimen thickness (and thus the optical path distance) and the specimen birefringence, before its light reaches the analyzer.

Implementing polarization control can be useful in a variety of imaging applications. Polarizers are placed over a light source, lens, or both, to eliminate glare from light scattering, increase contrast, and eliminate hot spots from reflective objects. This either brings out more intense color or contrast or helps to better identify surface defects or other otherwise hidden structures.

Adding image stabilization to a lens makes the lens a little heavier, which somewhat ironically increases the need for image stabilization.

Finally, there are also some brands, such as Sigma and Tamron, that produce 3rd-party lenses compatible with cameras from major manufacturers. These lenses typically aim to provide equal (or even better) image quality and features at a lower price point compared to the camera manufacturer’s own lenses.

While polarizers select certain polarizations of light, discarding the other polarizations, ideal waveplates modify existing polarizations without attenuating, deviating, or displacing the beam. They do this by retarding (or delaying) one component of polarization with respect to its orthogonal component. To help you determine which waveplate is best for your application, read Understanding Waveplates. Correctly chosen waveplates can convert any polarization state into a new polarization state and are most often used to rotate linear polarization, to convert linearly polarized light to circularly polarized light, or vice versa.

Birefringent polarizers rely on the dependence of the refractive index on the polarization of light. Different polarizations will refract at different angles and this can be used to select certain polarizations of light.

In amorphous solids such as glass and plastic, stress from temperature and pressure profiles in the material imparts localized variations and gradients in the material properties, making the material birefringent and nonhomogeneous. This can be quantified in transparent objects using the photoelastic effect, as stress and its related birefringence can be measured with polarized light methodologies.

Focus-by-wire systems focus more quickly than linear systems when using autofocus. However, they can be harder to focus when trying to focus manually. With a linear system, each position of the focus ring corresponds to a specific distance from the lens. This allows the manufacturers to put distance markers on the lenses, which is very helpful in some situations. With focus-by-wire, the position of the focus ring doesn’t correspond to a specific distance.

For linearly polarized light with intensity I0, the intensity transmitted through an ideal polarizer, I, can be described by Malus’ law,

Higher-end lenses often come with weather sealing, which is designed to keep out water and dust. It usually involves seals around switches, connections, and other areas that might allow the elements to sneak in. However, there’s no standard definition of weather sealing and weather sealing doesn’t mean weatherproof. Nonetheless, it’s a good idea to check for weather sealing when buying a lens if you plan to shoot outdoors in a challenging environment.

There’s also in-body image stabilization (IBIS). This is a system built into the camera to reduce camera shake, which is helpful when using a lens without image stabilization. Some systems combine IBIS with lens stabilization for better overall stabilization.

A parfocal lens is a type of camera lens that is able to maintain its focus plane even when the lens is zoomed in or out. This means that when the focal length of the lens is changed, the point of focus will remain the same, which can be useful in certain photography situations, such as when photographing a moving subject.

Most lenses these days are autofocus lenses. There is usually a switch on the lens, or an option in the camera’s menu, to change to manual focus if you want to fine-tune your focus or if the autofocus isn’t functioning properly, which can sometimes happen in low light situations if there isn’t enough contrast in the scene.

Digitalcamera lens components

While a lens can be as simple as a pinhole or a single lens element, modern camera lenses are typically created using multiple lenses in different groupings. These lenses have different shapes, materials, and qualities, and each group can have a different function within the entire lens system.

You may be able to limit it while shooting, too, by shooting at a higher f-stop. For example, on a lens with bad chromatic aberration, you’ll probably see more of it at lower f-stops than at higher f-stops. For example, you’ll get more fringing at f/4 than you will at f/16.

Many different types of microscopy techniques such as differential interference contrast (DIC) microscopy utilize polarizers to achieve a variety of effects.

Bokeh is a Japanese word meaning blur. It refers to the quality of the blurry areas of an image. Good bokeh has a smooth, creamy look to it while bad bokeh has a rougher look with distinct edges. For example, the edges of a bright point of light will blend smoothly into the background if a lens has “good” bokeh.

Camera lens componentsand functions

Lens manufacturers use different terms for image stabilization. Canon, for example, calls it Image Stabilization (IS). Nikon calls it Vibration Reduction (VR). For Sony, it’s Optical Steady Shot (OSS). Tamron uses Vibration Compensation (VC) and Sigma uses Optical Stabilization (OS). It’s all pretty much the same thing.

By cross-polarizing light with two linear polarizers that are oriented perpendicularly, hot spots can be reduced or eliminated altogether.

Hot spots are highly reflective portions of a field within a more diffuse reflecting field. In Figure 8, a polarizer is placed in front of the lens of a camera as well as over the light source illuminating the scene to reduce hot spots.

Lenses ideally exhibit minimal focus breathing, as it can result in changes in composition for still photographers, and an unwanted visual effect when shooting video.

Lens coatings can be applied to the front and/or rear elements of a lens and can be made from a variety of materials including polymers, metals, and ceramics.

Focus breathing is when the angle of view of a lens changes as the focus is changed. The name comes from the appearance of a lens “breathing” in and out as a photographer adjusts the focus ring back and forth.

A lens element is a single piece of glass or other transparent material that is used in a camera lens to refract (bend) light. Camera lenses can contain one or more lens elements, and the number and type of elements can vary depending on the design of the lens.