LensA lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic and are ground, polished, or molded to the required shape. A lens can focus light to form an , unlike a prism, which refracts light without focusing.
Camera lensA 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 . There is no major difference in principle between a lens used for a still camera, a video camera, a telescope, a microscope, or other apparatus, but the details of design and construction are different.
Zoom lensA zoom lens is a system of camera lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed-focal-length (FFL) lens (prime lens). A true zoom lens or optical zoom lens is a type of parfocal lens, one that maintains focus when its focal length changes. Most consumer zoom lenses do not maintain perfect focus, but are still nearly parfocal. Most camera phones that are advertised as having optical zoom actually use a few cameras of different but fixed focal length, combined with digital zoom to make a hybrid system.
MicrolensA microlens is a small lens, generally with a diameter less than a millimetre (mm) and often as small as 10 micrometres (μm). The small sizes of the lenses means that a simple design can give good optical quality but sometimes unwanted effects arise due to optical diffraction at the small features. A typical microlens may be a single element with one plane surface and one spherical convex surface to refract the light. Because micro-lenses are so small, the substrate that supports them is usually thicker than the lens and this has to be taken into account in the design.
Wide-angle lensIn photography and cinematography, a wide-angle lens refers to a lens whose focal length is substantially smaller than the focal length of a normal lens for a given film plane. This type of lens allows more of the scene to be included in the photograph, which is useful in architectural, interior, and landscape photography where the photographer may not be able to move farther from the scene to photograph it.
F-numberAn f-number is a measure of the light-gathering ability of any optical system like a camera lens or even the human eye. It is calculated by dividing the system's focal length by the diameter of the entrance pupil. The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, rate of light scattering, and exposure of a photograph. The f-number is dimensionless that is usually expressed using a lower-case hooked f with the format N, where N is the f-number.
Depth of fieldThe depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera. For cameras that can only focus on one object distance at a time, depth of field is the distance between the nearest and the farthest objects that are in acceptably sharp focus. "Acceptably sharp focus" is defined using a property called the "circle of confusion". The depth of field can be determined by focal length, distance to subject, the acceptable circle of confusion size, and aperture.
Diffraction-limited systemIn optics, any optical instrument or system a microscope, telescope, or camera has a principal limit to its resolution due to the physics of diffraction. An optical instrument is said to be diffraction-limited if it has reached this limit of resolution performance. Other factors may affect an optical system's performance, such as lens imperfections or aberrations, but these are caused by errors in the manufacture or calculation of a lens, whereas the diffraction limit is the maximum resolution possible for a theoretically perfect, or ideal, optical system.
Ray (optics)In optics, a ray is an idealized geometrical model of light or other electromagnetic radiation, obtained by choosing a curve that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow. Rays are used to model the propagation of light through an optical system, by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of ray tracing. This allows even very complex optical systems to be analyzed mathematically or simulated by computer.
Telephoto lensA telephoto lens, in photography and cinematography, is a specific type of a long-focus lens in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special lens group known as a telephoto group that extends the light path to create a long-focus lens in a much shorter overall design. The angle of view and other effects of long-focus lenses are the same for telephoto lenses of the same specified focal length.
