Camera lens

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 . 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. A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and 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: A pinhole camera with a large aperture is blurry because each pixel is essentially the shadow of the aperture stop, so its size is no smaller than the size of the aperture (third image). Here a pixel is the area of the detector exposed to light from a point on the object. Making the pinhole smaller improves resolution (up to a limit), but reduces the amount of light captured. At a certain point, shrinking the hole does not improve the resolution because of the diffraction limit. Beyond this limit, making the hole smaller makes the image blurrier as well as darker. 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?".