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Film Plane
A film plane is the surface of an image recording device such as a camera, upon which the lens creates the focused image. In cameras from different manufacturers, the film plane varies in distance from the lens. Thus each lens used has to be chosen carefully to assure that the image is focused on the exact place where the individual frame of film or digital sensor is positioned during exposure. It is sometimes marked on a camera body with the 'Φ' symbol where the vertical bar represents the exact location. Movie cameras often also have small focus hooks where the focus puller can attach one side of a tape measure to quickly gauge the distance to objects that the operator intends to bring into focus on the film. The measurement is taken from the film plane to the subject and effectively the film plane is the point in the camera where the film sits in the gate. Light measurements can also be taken at the film plane. Due to Petzval field curvature, the film plane upon which a lens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camera Lens
A camera lens, photographic lens or photographic objective is an optical lens (optics), lens or assembly of lenses (compound lens) used in conjunction with a camera body and mechanism to Imaging, make images of objects either on photographic film or on other media capable of storing an image Photosensitivity, chemically or Image sensor, electronically. 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 lens camera, interchangeable with lenses of different focal lengths, apertures, and other properties. While in principle a simple lens, 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 prese ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus (optics)
In geometrical optics, a focus, also called an image point, is a point where ray (optics), light rays originating from a point on the object vergence (optics), converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the circle of confusion, blur circle. This non-ideal focusing may be caused by optical aberration, aberrations of the imaging optics. Even in the absence of aberrations, the smallest possible blur circle is the Airy disc caused by diffraction from the optical system's aperture; diffraction is the ultimate limit to the light focusing ability of any optical system. Aberrations tend to worsen as the aperture diameter increases, while the Airy circle is smallest for large apertures. An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, and defocus aberration, out of focus if light is not well converged. The border between these is sometimes define ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photographic Film
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, and image resolution, resolution of the film. Film is typically segmented in ''frames'', that give rise to separate photographs. The emulsion will gradually darken if left exposed to light, but the process is too slow and incomplete to be of any practical use. Instead, a very short exposure (photography), exposure to the image formed by a camera lens is used to produce only a very slight chemical change, proportional to the amount of light absorbed by each crystal. This creates an invisible latent image in the emulsion, which can be chemically photographic processing, developed into a visible photograph. In addition to visible light, all films are sensitive to ultraviolet light, X-rays, gamma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Sensor
A digital sensor is an electronic or electrochemical sensor, where data is digitally converted and transmitted. Sensors are often used for analytical measurements, e.g. the measurement of chemical and physical properties of liquids. Examples of measured parameters are pH value, conductivity, oxygen, redox potentials. Such measurements are used in the industrialized world and give vital input for process control. Analog sensors were used in the past, but digital sensors have come to dominate in the age of microprocessors. The differences between the two types, and the reasons for the development of digital sensors are discussed: General aspects Digital sensors are the modern successors of analog sensors. Digital sensors replace analog sensors stepwise, because they overcome the traditional drawbacks of analog sensor systems (cf chapter 3 –which book?) History Electronic and electrochemical sensors are typically one part of a measuring chain. A measuring chain comprises the se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exposure (photography)
In photography, exposure is the amount of light per unit area reaching a frame (photography), frame of photographic film or the surface of an electronic image sensor. It is determined by shutter speed, lens f-number, and scene luminance. Exposure is measured in unit of measurement, units of lux-seconds (symbol lxs), and can be computed from exposure value (EV) and scene luminance in a specified region. An "exposure" is a single shutter cycle. For example, a long-exposure photography, long exposure refers to a single, long shutter cycle to gather enough dim light, whereas a multiple exposure involves a series of shutter cycles, effectively layering a series of photographs in one image. The accumulated ''photometric exposure'' (''H''v) is the same so long as the total exposure time is the same. Definitions Radiant exposure Radiant exposure of a ''surface'', denoted ''H''e ("e" for "energetic", to avoid confusion with Photometry (optics), photometric quantities) and measured in , i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Movie Camera
A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either onto film stock or an image sensor, in order to produce a moving image to display on a screen. In contrast to the still camera, which captures a single image at a time, the movie camera takes a series of images by way of an intermittent mechanism or by electronic means; each image is a ''frame'' of film or video. The frames are projected through a movie projector or a video projector at a specific frame rate (number of frames per second) to show the moving picture. When projected at a high enough frame rate (24 frames per second or more), the persistence of vision allows the eyes and brain of the viewer to merge the separate frames into a continuous moving picture. History A forerunner to the movie camera was the machine invented by Francis Ronalds at the Kew Observatory in 1845. A photosensitive surface was drawn slowly past the aper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus Puller
A focus puller or first assistant camera (1st AC) is a member of a film crew's camera department whose primary responsibility is to maintain the camera lens's optical focus on whatever subject or action is being filmed. "Pulling focus" refers to the act of changing the camera lens's focus distance to a moving subject's distance from the focal plane, or the changing distance between a stationary object and a moving camera. For example, if an actor moves from to away from the focal plane, the focus puller changes the lens's distance setting in precise relation to the actor's changing position. The focus puller may also shift focus from one subject to another as the shot requires, a process called "rack focusing". Focus pulling There is often very little room for error, depending on the parameters of a given shot. The focus puller's role is extremely important to a film production. In most circumstances, a "soft" image is considered unusable, as such an error can't be corrected i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tape Measure
A tape measure or measuring tape is a long, flexible ruler used to measure length or distance. It usually consists of a ribbon of cloth, plastic, fibreglass, or metal (usually - hard steel alloy) strip with linear measurement markings. Types Tape measures are often designed for specific uses or trades. Tapes may have different scales, be made of different materials, and be of different lengths depending on the intended use. Tape measures used in sewing, tailoring are called "sewing tape". Originally made from flexible cloth or plastic, fiberglass is now the preferred material due to its resistance from stretching or tearing. Sewing tape is mainly used for the measuring of the subject's waist line.Measuring tapes designed for carpenter, carpentry or construction often use a curved metallic ribbon that can remain stiff and straight when extended, but can also retract into a coil for convenient storage. This type of tape measure will have a hook on the end to aid measuring. The hoo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petzval Field Curvature
Petzval field curvature, named for Joseph Petzval, describes the optical aberration in which a flat object normal to the optical axis (or a non-flat object past the hyperfocal distance) cannot be brought properly into focus on a flat image plane. Field curvature can be corrected with the use of a '' field flattener'', designs can also incorporate a curved focal plane like in the case of the human eye in order to improve image quality at the focal surface. Analysis Consider an "ideal" single-element lens system for which all planar wave fronts are focused to a point at distance ''f'' from the lens. Placing this lens the distance ''f'' from a flat image sensor, image points near the optical axis will be in perfect focus, but rays off axis will come into focus before the image sensor, dropping off by the cosine of the angle they make with the optical axis. This is less of a problem when the imaging surface is spherical, as in the human eye The human eye is a sensory organ in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photographic Plate
Photographic plates preceded film as the primary medium for capturing images in photography. These plates, made of metal or glass and coated with a light-sensitive emulsion, were integral to early photographic processes such as heliography, daguerreotypes, and photogravure. Glass plates, thinner than standard window glass, became widely used in the late 19th century for their clarity and reliability. Although largely replaced by film during the 20th century, plates continued to be used for specialised scientific and medical purposes until the late 20th century. History Glass plates were far superior to film for research-quality imaging because they were stable and less likely to bend or distort, especially in large-format frames for wide-field imaging. Early plates used the wet collodion process. The wet plate process was replaced late in the 19th century by gelatin dry plates. A view camera nicknamed "The Mammoth" weighing was built by George R. Lawrence in 1899, sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Focus
In a photograph, the area of critical focus is the portion of the picture that is optically in focus. This does not relate to depth of field which describes apparent sharpness. Reducing the size of the aperture will increase the depth of field but the plane of critical focus will not change. Depth of field extends away from the plane of critical sharpness. The image is only critically in focus within a plane. The formula that describes the relationship between plane of sharpness, lens and film is :1/I+1/O = 1/F, where I is the film to lens distance, O is the distance from the lens to the plane of critical focus (in the object space), and F is the focal length of the lens. 'Critical Focus' is also the title of a regular column by Brian J. Ford in the American magazin''The Microscope'' See also *Sharpness (visual) In photography, acutance describes a subjective perception of visual acuity that is related to the edge contrast of an image. Acutance is related to the magnitu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cardinal Point (optics)
In Gaussian optics, the cardinal points consist of three pairs of Point (geometry), points located on the optical axis of a Rotational symmetry, rotationally symmetric, focal, optical system. These are the ''Focus (optics), focal points'', the principal points, and the nodal points; there are two of each. For ''ideal'' systems, the basic imaging properties such as image size, location, and orientation are completely determined by the locations of the cardinal points. For simple cases where the medium on both sides of an optical system is air or vacuum four cardinal points are sufficient: the two focal points and either the principal points or the nodal points. The only ideal system that has been achieved in practice is a plane mirror, however the cardinal points are widely used to the behavior of real optical systems. Cardinal points provide a way to analytically simplify an optical system with many components, allowing the imaging characteristics of the system to be approximatel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
