A greatly simplified view of the human eye is shown below. The pupil is a little hole which allows light to pass into the eye. Behind the pupil lies the eye's lens. Muscles in the eye control the size of the pupil and the shape of the lens, thereby adjusting the amount of light that enters they eye and the focus of the lens.
The retina is a sensitive layer of nerves at the back of the eyeball; incident light upon the retina is translated into a coherent image by the brain. Many people do not have perfect vision; that is, a lot of people have eyes whose lenses do not focus light properly on the retina. Two well-known vision problems correctible via eyeglasses are nearsightedness picture a above and farsightedness picture c.
Nearsightedness focusses rays of light in front of the retina, while farsightedness focusses rays behind the retina. A diverging lens can correct nearsightedness by bending incoming light rays outwards, so that the eye's lens which usually bends incoming rays too much focusses the light closer to the retina picture b.
A converging lens similarly corrects farsightedness picture d 1. In our study of lenses, we saw that if the source was placed within a focal length of a converging lens, the lens yielded a magnified image on the same side of the lens as the source.
This is, of course, the detective's best friend, the magnifying glass. The amount of magnification, as we know from our treatment of lenses, depends on the distance of the source from the lens, and the refractive index of the lens material.
The aperture, which lets light into the inside of the camera, corresponds to the pupil. The system of lenses in a camera performs the same function as the lens of the eye. However, whereas the lens of the eye changes shape to change focus, glass lenses are not very forgiving of shape changes. Instead, the lens system can be slid along its optical axis in order to focus on the film.
Of course, the film plays the role of the retina. In addition, cameras have a shutter, which opens and closes quickly so that the film does not get inundated with light.
This produces a more or less clear image of the instant that the photographer shoots. Simple microscopes use lens systems to magnify very small objects, as illustrated in the following diagram.
An object S 1 too small to examine with the naked eye is placed just outside the focus F o of the objective lens in the microscope above. Tracing the infinite and central rays as we have before, we can find the location of the image I 1.As a photographer, you have a vast selection of lens options to choose from. Wide angle lenses are a popular choice, but what is a wide angle lens used for?
Is wide angle the best lens choice for you? Product links on ExpertPhotography are referral links. If you use one of these and buy something we make a little bit of money.
Need more info? See how it all works here. The most common description is that a wide angle lens displays a wider field of view than our vision. So, What mm is a wide angle lens? The popular definition is that a lens below, or equivalent to 35mm is considered a wide angle lens.
This is roughly 65 degrees of diagonal field of view. All lenses, including wide angle lenses, come in either a prime or a zoom version. A prime lens has a fixed short focal lengthmeaning you have to get closer to a subject by moving physically.
Primes are generally lighter, faster, cheaper and produce better image quality. A zoom lens has a variable focal length zoom range. Most zoom lenses are more specific, giving you one or two of these.
What Is a Wide Angle Lens (And When to Use One!)
Zoom lenses very versatile, allowing to keep your gear to a minimum. But, generally, a zoom lens is heavier and more expensive, due to extra mechanisms and glass inside the lens. Kit lenses are exceptions, but they often come with compromises. Their image quality is often surpassed by prime lenses. They are very much a jack of all trades, master of none. We have to make a disclaimer here. Smaller sensors crop out the centre portion of any lens, resulting in a tighter field of view. For simplification, all focal lengths mentioned here are full-frame equivalent.
If you want to know how these translate to your camera, divide them by 1. We know that wide angle means anything below 35mm. But what is the best size for a wide angle lens?
The most popular wide angle zoom range is mm. Most kit or standard zoom lenses go down to 24mm or 28mm. The widest lenses on the market are 10mm rectilinear and 8mm fisheye. Fish-eye lenses are special ultra-wide angle lenses.A camera lens also known as photographic lens or photographic objective is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.
There is no major difference in principle between a lens used for a still cameraa video cameraa telescopea microscopeor other apparatus, but the details of design and construction are different. A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengthsaperturesand other properties. While in principle a simple convex lens will suffice, in practice a compound lens made up of a number of optical lens elements is required to correct as much as possible the many optical aberrations that arise.
Some aberrations will be present in any lens system. It is the job of the lens designer to balance these and produce a design that is suitable for photographic use and possibly mass production. Typical rectilinear lenses can be thought of as "improved" pinhole "lenses". As shown, a pinhole "lens" is simply a small aperture that blocks most rays of light, ideally selecting one ray to the object for each point on the image sensor.
Pinhole lenses have a few severe limitations:. Practical lenses can be thought of as an answer to the question: "how can a pinhole lens be modified to admit more light and give a smaller spot size? A first step is to put a simple convex lens at the pinhole with a focal length equal to the distance to the film plane assuming the camera will take pictures of distant objects . This allows the pinhole to be opened up significantly fourth image because a thin convex lens bends light rays in proportion to their distance to the axis of the lens, with rays striking the center of the lens passing straight through.
The geometry is almost the same as with a simple pinhole lens, but rather than being illuminated by single rays of light, each image point is illuminated by a focused "pencil" of light rays. Principle of a pinhole camera. Light rays from an object pass through a small hole to form an image. With a small pinhole light is reduced, but diffraction prevents the image spot from getting arbitrarily small.
From the front of the camera, the small hole the aperturewould be seen. If one were inside the camera, one would see the lens acting as a projector.
The Uses of Lenses in Optical Devices
The virtual image of the aperture from inside the camera is the lens's exit pupil. In this simple case, the aperture, entrance pupil, and exit pupil are all in the same place because the only optical element is in the plane of the aperture, but in general these three will be in different places. Practical photographic lenses include more lens elements. The additional elements allow lens designers to reduce various aberrations, but the principle of operation remains the same: pencils of rays are collected at the entrance pupil and focused down from the exit pupil onto the image plane.
A camera lens may be made from a number of elements: from one, as in the Box Brownie 's meniscus lens, to over 20 in the more complex zooms. These elements may themselves comprise a group of lenses cemented together. The front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion, flareand surface reflectanceand to adjust color balance.
To minimize aberration, the curvature is usually set so that the angle of incidence and the angle of refraction are equal. In a prime lens this is easy, but in a zoom there is always a compromise. The lens usually is focused by adjusting the distance from the lens assembly to the image plane, or by moving elements of the lens assembly. To improve performance, some lenses have a cam system that adjusts the distance between the groups as the lens is focused.All DSLR systems offer a dizzying selection of lenses for their cameras.
Next is to find out what their budget is. The cost of the lens depends on several things. Less expensive lenses will generally have variable apertures, meaning as you zoom, the maximum aperture gets smaller. More expensive lenses have a fixed aperture. The good news is that all major camera and lens manufacturers offer a variety of focal lengths to satisfy most budgets.Converging and Diverging Lens
After those two questions are answered it becomes more difficult. I started my career as a sports photographer and rarely used anything shorter than aoften going for mm f2. As I began shooting landscapes as more of a hobby, I began to discover the magic of wide angles.
Wide angles give a wide expansive view, and when used correctly, can wrap you in the scene. Wide angles should be used when prominent foreground objects are present.
The primary mistake made by new photographers is to use wide angles incorrectly- by not being close enough, having no interest in the foreground, or by trying to include too much in the scene.
Wide angles are also handy in tight areas, like small rooms, cars, caves, etc.
They can give volume to the small area. Wide angles have the potential to drastically change your photography. Standard lenses tend to range from about 35mm up to around 85mm. Lenses in the standard zoom range will cover moderate wide angles- typically 24mm to 35mm, to moderate telephoto lengths- around 70mm and up to about mm.
They are versatile, allowing both for wide angle work such as a landscape, or zooming in to the telephoto end of the lens to take a great portrait. Standard zooms are generally included in many SLR kits that come with lenses. However, there are also standard prime lenses. Prime lenses are lenses that are just one focal length. When I was a student, everyone in the class started with a 50mm lens. Whether you choose a zoom or a prime is up to you.
More often than not, when I speak to neophyte photographers looking to purchase their next lens, they are looking for something on the telephoto end.
The most popular seems to be various flavors of mm or mm. These lenses are excellent when used properly. However, too often, telephoto zooms allow the photographer to become lazy.
Uses of Mirrors & Lenses
Telephoto lenses compress distance, making everything appear closer, as opposed to wide angles which distort perspective and make things look further away. This can be useful for landscapes when you want the sun or moon to appear large in comparison to other objects in the image. In this shot of Shenandoah Valley at sunset, the telephoto lens compresses the distance, making the layers of mountains and mist look almost flat.
Of course, telephoto lenses are also excellent for sports, nature, and wildlife, where it can be difficult to get close. Sports, however, presents its own set of challenges. To be able to stop action without blurring, you need to use a fast shutter speed. Typically, faster telephoto lenses are required. Faster telephoto lenses have larger maximum apertures. These lenses are great for getting you closer to the action, but you need to be sure your shutter speed is fast enough.The lens is the transparent medium that refracts the light and it is limited with two spherical surfacesThe lens is usually made of the glass or the plasticThe lens is the transparent optical device that affects the focus of a light beam through the refraction.
A simple lens consists of a single piece of material while a compound lens consists of several simple lenses the elementsusually along a common axis. The devices that similarly refract radiation other than visible light are also called the lenses such as the microwave lenses or the acoustic lenses. Convex lens and concave lens. The lenses are used in many thingsThey are used in the medical eye glasses either for reading or walkingThey are used in the warsthe leaders use the binoculars to follow the battles.
The person who fixes the watches use a magnifier lens to see the minute parts of the watchesThe lenses are used in the manufacture of many things as the projectorthe cameras and the magnifying lenses. The lenses are used in designing some of optical devices such as Telescopes which are used for formation enlarged images for the heavenly bodies.
The lenses are used in Microscopes which are used for formation magnified images of the tiny bodies that can not be seen with the naked eye and they are used in making of medical glasses to treat the vision defects. There are two types of the lenses which are the convex lens and the concave lens. The convex lens is thick at the center and less thickness at the tipsIt collects the light rays falling on itSoit is called the converging lens.
The concave lens is thin at its center and more thick at the tipsIt separates the light raysSoit is called the diverging lens. T he center of the curvature of the lens face C is the center of the spherewhere this face is a part of itThe optical center of the lens is a point inside the lens lies on the principal axis in the mid distance between its faces. T he focus of the lens F the principal focus is the point of collection of the refracted light rays in the convex lens or their extensions in the concave lensIt is produced when a beam of parallel rays falls parallel to the principal axis of a lens.
The lens has two centers of curvature and it has two foci because it has two circular surfaces. Properties of the formed images by convex lens and concave lens. The uses of lenses to treat the vision defects. November 29, June 10, January 16, Your email address will not be published. Uses of the concave mirror and the convex mirror in our daily life.
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Windows 10 advantages and disadvantages.Lensin opticspiece of glass or other transparent substance that is used to form an image of an object by focusing rays of light from the object. A lens is a piece of transparent material, usually circular in shape, with two polished surfaces, either or both of which is curved and may be either convex bulging or concave depressed.
The curves are almost always spherical; i. A lens has the valuable property of forming images of objects situated in front of it. Single lenses are used in eyeglassescontact lenses, pocket magnifiers, projection condensers, signal lights, viewfinders, and on simple box cameras.
More often a number of lenses made of different materials are combined together as a compound lens in a tube to permit the correction of aberrations. Compound lenses are used in such instruments as cameras, microscopes, and telescopes. A lens produces its focusing effect because light travels more slowly in the lens than in the surrounding air, so that refractionan abrupt bending, of a light beam occurs both where the beam enters the lens and where it emerges from the lens into the air.
A single lens has two precisely regular opposite surfaces; either both surfaces are curved or one is curved and one is plane. Lenses may be classified according to their two surfaces as biconvex, plano-convex, concavo-convex converging meniscusbiconcave, plano-concave, and convexo-concave diverging meniscus. Because of the curvature of the lens surfaces, different rays of an incident light beam are refracted through different angles, so that an entire beam of parallel rays can be caused to converge on, or to appear to diverge from, a single point.
This point is called the focal pointor principal focus, of the lens often depicted in ray diagrams as F. Refraction of the rays of light reflected from or emitted by an object causes the rays to form a visual image of the object. This image may be either real —photographable or visible on a screen—or virtual —visible only upon looking into the lens, as in a microscope.
The image may be much larger or smaller than the object, depending on the focal length of the lens and on the distance between the lens and the object. The focal length of a lens is the distance from the centre of the lens to the point at which the image of a distant object is formed. A long-focus lens forms a larger image of a distant object, while a short-focus lens forms a small image.
Usually the image formed by a single lens is not good enough for precise work in such fields as astronomy, microscopy, and photography; this is because the cone of rays emitted by a single point in a distant object is not united in a perfect point by the lens but instead forms a small patch of light. To correct such aberrations, it is often necessary to combine in one mount several lens elements single lensessome of which may be convex and some concave, some made of dense high-refractive or high-dispersive glass, and others made of low-refractive or low-dispersive glass.
The lens elements may be cemented together or mounted at carefully calculated separations to correct the aberrations of the individual elements and obtain an image of acceptable sharpness see also aberration.
The precise mounting also ensures that all lenses are properly centred; that is, the centres of curvature of all the lens surfaces lie on a single straight line called the principal axis of the lens. A frequently used measure of the quality of any lens system is its ability to form an image that is sharp enough to separate, or resolve, two very close dots or lines in an object. Resolving power depends on how well the various aberrations in a lens system are corrected.
The simplest compound lens is a thin cemented combination of two single lenses, such as that used in the objective the lens nearest the object of a small refracting telescope.
Microscope objectives may contain as many as eight or nine elements, some of which may be made of different materials in order to bring all colours of light to a common focus, and thus prevent chromatic aberration.
The objective lenses used in cameras may contain from two to 10 elements, while a so-called zoom or variable-focal length lens may have as many as 18 or 20 elements in several groups, the different groups being movable along the axis by levers or cams in order to produce the desired change in focal length without a shift of the focal plane.Follow-up on this answer.
Related Questions. Still Curious? Lenses are used to focus light. Because focusing light is so important, you can find lenses in many places. Perhaps the most common lens that we see are the ones in peoples glasses. There is a small lens in each of our eyes. When that lens isn't shaped quite right, light doesn't focus clearly and it's hard to see things. Glasses put another lens in front of the eye to help focus the light better for us. Then we can see clearly.
Choosing Lenses: When to Use Which Lens and Why
Another place to find a lens in in a CD player. A CD player works by shining a laser which is a type of light onto a disc. The lens in the CD player helps focus the laser onto the disc. Without that lens, the CD player can't read anything.
Lenses are also used in telescopes. When we look up at the sky, we see lots of stars. But we can use a telescope to look at a specific star. The lenses in the telescope focus the light from a single star so that the star we're looking at appears larger so it is easier to see.
What are the uses of concave and convex lens in day to day life? Hi, Mayank. It should come as no surprise to you that convex lenses are much more widely used than concave in day-to-day life. This is because convex lenses magnify images, or make them appear larger. For this reason, a single convex lens fitted to a frame or handle is called a magnifying glass or magnifying lens. Convex lenses cause incident light rays to convergecreating a point of greater light intensity as seen below.
For this reason, large convex lenses have been used since antiquity as burning-glasses.