A toy camera is a simple, inexpensive film camera.
133-466: Despite the name, toy cameras are fully functional and capable of taking photographs, though with optical aberrations due to the limitations of their simple lenses . From the 1990s onward, there has been interest in the artistic use of such cameras or recreation of this style, both with cameras originally designed for children, and others originally intended as mass-market consumer cameras. Many professional photographers have used toy cameras and exploited
266-476: A camera or the camera is switched off, changing the focus is impossible. All stepping-motor lenses are marked with the letters "STM" on the front of the lens as part of the model designation. The image stabilization (IS) technology detects handheld motion and optically corrects it. It only corrects handheld motion; if the subject of the photograph is moving, IS will not stop it. It also can only stabilize so much motion, ranging from two to five stops, depending on
399-408: A certain number of aberrations is associated. This connection is only supplied by theories which treat aberrations generally and analytically by means of indefinite series. A ray proceeding from an object point O (fig. 5) can be defined by the coordinates (ξ, η). Of this point O in an object plane I, at right angles to the axis, and two other coordinates (x, y), the point in which the ray intersects
532-633: A constant maximum aperture. All L lenses are supplied complete with a hood and a pouch or case, which are not generally included with non-L lenses. Distinctive visual cues include a red ring around the lens and an off-white colour on longer-focal-length models. The latter also helps to reflect light and reduce heat absorption and subsequent internal expansion of lens components that can affect the image quality of long focal length lenses. All L lenses include at least one fluorite , ultra-low- dispersion glass element, super ultra-low- dispersion glass element, and/or certain types of aspherical elements . (Note that
665-441: A definite value, w*, zones of astigmatism, curvature of field and distortion, attend smaller values of w. The practical optician names such systems: corrected for the angle of aperture u* (the height of incidence h*) or the angle of field of view w*. Spherical aberration and changes of the sine ratios are often represented graphically as functions of the aperture, in the same way as the deviations of two astigmatic image surfaces of
798-512: A disk of confusion; this is similar to the confusion caused by two zones in spherical aberration. For infinitely distant objects the radius Of the chromatic disk of confusion is proportional to the linear aperture, and independent of the focal length ( vide supra , Monochromatic Aberration of the Axis Point ); and since this disk becomes the less harmful with an increasing image of a given object, or with increasing focal length, it follows that
931-443: A given object upon a given plane with given magnification (insofar as aberrations must be taken into account) could be dealt with by means of the approximation theory; in most cases, however, the analytical difficulties were too great for older calculation methods but may be ameliorated by application of modern computer systems. Solutions, however, have been obtained in special cases. At the present time constructors almost always employ
1064-518: A gold ring and the word "Ultrasonic" printed in gold on the lens barrel. L lenses with USM don't have the gold ring, but they still have the word "Ultrasonic" printed on the lens barrel. Canon announced stepping motor (STM) lenses first in June 2012, alongside the EOS 650D/Rebel T4i/Kiss X6i . Canon stated that this technology allows smooth and silent autofocus, and with compatible bodies (the first of which
1197-468: A high numerical aperture , and in characterizing optical systems with respect to their aberrations. The preceding review of the several errors of reproduction belongs to the Abbe theory of aberrations, in which definite aberrations are discussed separately; it is well suited to practical needs, for in the construction of an optical instrument certain errors are sought to be eliminated, the selection of which
1330-605: A manual connection, the aperture and focus controls of the lens cannot be controlled or read from the camera; the lens must be focused manually. Since the only possible metering is through-the-lens, the lens must be manually stopped down to accurately meter at anything less than full aperture. (This is called stop-down metering .) Compatible third-party lenses with the EF lens mount are manufactured by Yongnuo , Samyang , Schneider , Sigma , Tamron , Tokina , Cosina and Carl Zeiss . The manufacturers of these lenses have reverse engineered
1463-481: A number of controls, switches and physical features, used by the photographer to control the lens. The types and number of the controls can vary from lens to lens. With the most basic lenses having only a few, to the most complex having over a dozen different controls and switches. This is a list of the different controls and switches found on most Canon EF lenses, along with a detailed description on what they are used for. Lens mount index: This raised, round red mark
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#17328009846801596-485: A number of non-L lenses also use aspherical elements, and at least one non-L lens has a Super UD element.) Most L lenses feature an ultrasonic motor (USM) for focusing. In 1987 Canon was the first to use USM (Ultra Sonic Motor) with the Canon EF 300mm f/2.8L USM. In 1989 Canon was the first to create a full frame f/1.0 AF (AutoFocus) lens and the only one until today with the Canon EF 50mm f/1.0L USM. In 1993 Canon
1729-416: A plane between O' and O" a circle of least confusion. The interval O'O", termed the astigmatic difference, increases, in general, with the angle W made by the principal ray OP with the axis of the system, i.e. with the field of view. Two astigmatic image surfaces correspond to one object plane; and these are in contact at the axis point; on the one lie the focal lines of the first kind, on the other those of
1862-414: A point which subtends a finite angle at the system) is, in general, even then not sharply reproduced if the pencil of rays issuing from it and traversing the system is made infinitely narrow by reducing the aperture stop; such a pencil consists of the rays which can pass from the object point through the now infinitely small entrance pupil. It is seen (ignoring exceptional cases) that the pencil does not meet
1995-434: A portion of a plane perpendicular at O to the axis will be also concurrent, even if the part of the plane be very small. As the diameter of the lens increases (i.e., with increasing aperture), the neighboring point N will be reproduced, but attended by aberrations comparable in magnitude to ON. These aberrations are avoided if, according to Abbe, the sine condition, sin u'1/sin u1=sin u'2/sin u2, holds for all rays reproducing
2128-431: A resemblance to a comet having its tail directed towards or away from the axis. From this appearance it takes its name. The unsymmetrical form of the meridional pencil—formerly the only one considered—is coma in the narrower sense only; other errors of coma have been treated by Arthur König and Moritz von Rohr, and later by Allvar Gullstrand. If the above errors be eliminated, the two astigmatic surfaces united, and
2261-510: A set of fitting coefficients that individually represent different types of aberrations. These Zernike coefficients are linearly independent , thus individual aberration contributions to an overall wavefront may be isolated and quantified separately. There are even and odd Zernike polynomials. The even Zernike polynomials are defined as and the odd Zernike polynomials as where m and n are nonnegative integers with n ≥ m {\displaystyle n\geq m} , Φ
2394-409: A sharp image obtained with a wide aperture—there remains the necessity to correct the curvature of the image surface, especially when the image is to be received upon a plane surface, e.g. in photography. In most cases the surface is concave towards the system. Even if the image is sharp, it may be distorted compared to ideal pinhole projection . In pinhole projection, the magnification of an object
2527-528: A single pair of planes (e.g. for a single focus setting of an objective), however, the problem can in principle be solved perfectly. Examples of such a theoretically perfect system include the Luneburg lens and the Maxwell fish-eye . Practical methods solve this problem with an accuracy which mostly suffices for the special purpose of each species of instrument. The problem of finding a system which reproduces
2660-514: A single point after transmission through the system. Aberrations occur because the simple paraxial theory is not a completely accurate model of the effect of an optical system on light, rather than due to flaws in the optical elements. An image-forming optical system with aberration will produce an image which is not sharp. Makers of optical instruments need to correct optical systems to compensate for aberration. Aberrations are particularly impactful in telescopes, where they can significantly degrade
2793-573: A sufficiently large number of higher-order Zernike polynomials. However, wavefronts with very steep gradients or very high spatial frequency structure, such as produced by propagation through atmospheric turbulence or aerodynamic flowfields , are not well modeled by Zernike polynomials, which tend to low-pass filter fine spatial definition in the wavefront. In this case, other fitting methods such as fractals or singular value decomposition may yield improved fitting results. The circle polynomials were introduced by Frits Zernike to evaluate
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#17328009846802926-469: A thin positive lens, O'2 will lie in front of O'1 so long as the angle u2 is greater than u1 ( under correction ); and conversely with a dispersive surface or lenses ( over correction ). The caustic, in the first case, resembles the sign > (greater than); in the second < (less than). If the angle u1 is very small, O'1 is the Gaussian image; and O'1 O'2 is termed the longitudinal aberration, and O'1R
3059-469: Is "barrel distortion", in which the center of the image is magnified more than the perimeter (figure 3a). The reverse, in which the perimeter is magnified more than the center, is known as "pincushion distortion" (figure 3b). This effect is called lens distortion or image distortion , and there are algorithms to correct it. Systems free of distortion are called orthoscopic (orthos, right, skopein to look) or rectilinear (straight lines). This aberration
3192-537: Is a property of optical systems, such as lenses , that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration. Aberration can be defined as a departure of the performance of an optical system from the predictions of paraxial optics . In an imaging system, it occurs when light from one point of an object does not converge into (or does not diverge from)
3325-455: Is desired. The "set" button is used for saving the focus distance into memory. The focus preset ring is used for recalling the memory save point. It is a thin knurled ring, usually located in front of the Focusing ring . To use this feature, one must set the switch to either "on" or "on with sound", focus the lens to the desired distance, then press the "set" button. After this, when the feature
3458-445: Is doing infrared photography, as lenses typically focus infrared light at a different point than visible light, and therefore achieving correct focus using visible light will result in an out-of-focus infrared image. To make an adjustment, first focus the subject, then turn the Focusing ring so it matches the corresponding infrared index mark. Focus mode switch: This switch is found on most EF lenses that have an autofocus feature. It
3591-482: Is found on all EF lenses that feature an image stabilizer. It is used for turning the image stabilizer "on"( | ), or "off"( o ). Image stabilizer mode switch: This switch is found on many EF lenses that feature an image stabilizer, particularly those of longer focal lengths. The switch has two settings on most lenses: Mode 1 and Mode 2. The newest IS Mark II versions of certain EF super telephoto lenses (the 300mm f/2.8L, 400mm f/2.8L, 500mm f/4L, and 600mm f/4L ), plus
3724-403: Is found on all EF lenses. It is used for matching the EF lens mount to the mount on an EOS body, so one can connect the lens to the body quickly. Focusing ring: This control, found on most EF lenses, is used for focusing the lens. It is usually a ring on the lens body, that can be turned. Zoom ring: This control is found on most EF zoom lenses . It is used for changing the focal length of
3857-415: Is found on most super telephoto EF lenses. The focus preset feature uses one switch, one button, and one ring. It is used for presetting a given focus distance into memory, so that the photographer can quickly recall the focus distance, without the need for autofocus. The switch has three settings "off"( o ), "on"( | ), or "on with sound"( ( ( - ), and is used for turning on the feature, and deciding if sound
3990-462: Is inspired by the formerly state-run optics manufacturer, LOMO PLC of Saint Petersburg , Russia that created and produced the 35 mm LOMO LC-A Compact Automat camera, now central to Lomography. This camera was loosely based upon the Cosina CX-1 introduced in the early 1980s. The LOMO LC-A produces "unique, colorful, and sometimes blurry" images. The Lomographic Society International
4123-443: Is inversely proportional to its distance to the camera along the optical axis so that a camera pointing directly at a flat surface reproduces that flat surface. Distortion can be thought of as stretching the image non-uniformly, or, equivalently, as a variation in magnification across the field. While "distortion" can include arbitrary deformation of an image, the most pronounced modes of distortion produced by conventional imaging optics
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4256-456: Is justified by experience. In the mathematical sense, however, this selection is arbitrary; the reproduction of a finite object with a finite aperture entails, in all probability, an infinite number of aberrations. This number is only finite if the object and aperture are assumed to be infinitely small of a certain order ; and with each order of infinite smallness, i.e. with each degree of approximation to reality (to finite objects and apertures),
4389-540: Is named after the Soviet-era cameras produced by the L eningradskoye O ptiko- M ekhanicheskoye O byedinenie (LOMO). Lomography has been a highly social pursuit since 1992, with local and international events organised by The Lomographic Society International (Lomography, a commercial company selling analogue cameras, films and accessories). The company continues to promote the Lomographic style; however, it
4522-419: Is not necessary to use the company's products to take Lomographic photos. "Lomography" is claimed as a commercial trademark by The Lomographic Society International, associated with a photographic image style and a film camera movement and international Lomography Community. However, it has become a genericised trademark ; most camera phone photo editor apps include a "lomo" filter . The Lomography name
4655-400: Is odd. The first few Zernike polynomials, multiplied by their respective fitting coefficients, are: where ρ {\displaystyle \rho } is the normalized pupil radius with 0 ≤ ρ ≤ 1 {\displaystyle 0\leq \rho \leq 1} , ϕ {\displaystyle \phi } is the azimuthal angle around
4788-414: Is often employed provisionally, since its accuracy does not generally suffice. In order to render spherical aberration and the deviation from the sine condition small throughout the whole aperture, there is given to a ray with a finite angle of aperture u* (width infinitely distant objects: with a finite height of incidence h*) the same distance of intersection, and the same sine ratio as to one neighboring
4921-497: Is possible to mount lenses using the Nikon F mount , Olympus OM, Leica R and universal M42 lens mounts (among others) by the use of a mechanical adapter without electronic control of the aperture or autofocus. In contrast, parfocal adaptation of EF lenses to non-EF camera bodies is not possible with only a mechanical adapter that does not contain optical elements. EF mount lenses are somewhat compatible with newer Canon bodies, though
5054-423: Is quite distinct from that of the sharpness of reproduction; in unsharp, reproduction, the question of distortion arises if only parts of the object can be recognized in the figure. If, in an unsharp image, a patch of light corresponds to an object point, the center of gravity of the patch may be regarded as the image point, this being the point where the plane receiving the image, e.g., a focusing screen, intersects
5187-407: Is termed achromatic. A system is said to be chromatically under-corrected when it shows the same kind of chromatic error as a thin positive lens, otherwise it is said to be overcorrected. If, in the first place, monochromatic aberrations be neglected — in other words, the Gaussian theory be accepted — then every reproduction is determined by the positions of the focal planes, and the magnitude of
5320-415: Is the azimuthal angle in radians , and ρ is the normalized radial distance. The radial polynomials R n m {\displaystyle R_{n}^{m}} have no azimuthal dependence, and are defined as and R n m ( ρ ) = 0 {\displaystyle R_{n}^{m}(\rho )=0} if n − m {\displaystyle n-m}
5453-407: Is the 650D) will provide continuous autofocus in live view and video. Unlike USM, STM lenses use focus-by-wire to enable full-time manual mode. Two main disadvantages are linked to focus-by-wire: First, the need to computationally process the input before the intended action is executed leads to a sometimes perceptible lag. Second, using the motor requires power, so when an STM lens is not connected to
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5586-417: Is the angle u subtended by the entrance pupil at this point, the magnitude of the aberration will be determined by the position and diameter of the entrance pupil. If the system be entirely behind the aperture stop, then this is itself the entrance pupil ( front stop ); if entirely in front, it is the exit pupil ( back stop ). If the object point be infinitely distant, all rays received by the first member of
5719-417: Is the projection of a single plane onto another plane; but even in this, aberrations always occurs and it may be unlikely that these will ever be entirely corrected. Let S (fig. 1) be any optical system, rays proceeding from an axis point O under an angle u1 will unite in the axis point O'1; and those under an angle u2 in the axis point O'2. If there is refraction at a collective spherical surface, or through
5852-548: Is turned on, the photographer can turn the focus preset ring, and the lens will recall and focus quickly to the distance that was saved. This feature is useful for sports and birding photography (for instance, to allow rapid focusing on the goal or on a spot where the birds may perch). Filter mounting: This mount is used for attaching filters to EF lenses. There are three types: front threaded mount, inner drop-in mount, and rear gelatin holders. Front threaded filters are used on most lenses, and are attached by threading and tightening
5985-405: Is used for setting the lens to either autofocus mode, or manual focus. When set to autofocus mode (AF), the lens will autofocus when directed to by the camera. When set to manual focus (MF), the lens is focused using the Focusing ring . Some lenses support full-time manual focusing (FT-M), which allows the photographer to focus the lens manually even with the mode switch set to AF, without damaging
6118-581: Is used to bring down the cost of the lens. It is possible to implement FT-M even with micromotor USM; however, it requires additional mechanical components, and the vast majority of micro-USM lenses do not offer such capability. Nano USM was introduced in 2016 with the release of Canon's latest iteration of the EF-S 18–135mm lens . It is intended to offer the AF speed of ring-type USM with the quietness of STM mechanisms (see below). Some older USM lenses are identified with
6251-408: Is used. The most common monochromatic aberrations are: Although defocus is technically the lowest-order of the optical aberrations, it is usually not considered as a lens aberration, since it can be corrected by moving the lens (or the image plane) to bring the image plane to the optical focus of the lens. In addition to these aberrations, piston and tilt are effects which shift the position of
6384-408: Is useful to the photographer for determining, or setting, the lens's focus distance. It is used in conjunction with the Focusing ring . When rotated, the distance scale will also rotate to show the changing focus distance. On some lenses the distance scale also has an infrared index. These are shown as red markings below the distance scale. This is used for making focus adjustments when the photographer
6517-475: The Canon EF-S 18-200mm lens , are able to detect if they are being panned in either axis and will automatically disable the stabilization for the axis parallel to movement and therefore do not require this switch. Autofocus stop buttons: These buttons are found on some super telephoto EF lenses, evenly spaced around the front collar of the lens. They are used for temporarily stopping the autofocus feature of
6650-405: The characteristic function of the system and its differential coefficients, instead of by the radii, &c., of the lenses; these formulae are not immediately applicable, but give, however, the relation between the number of aberrations and the order. Sir William Rowan Hamilton (British Assoc. Report, 1833, p. 360) thus derived the aberrations of the third order; and in later times the method
6783-409: The lateral aberration of the pencils with aperture u2. If the pencil with the angle u2 is that of the maximum aberration of all the pencils transmitted, then in a plane perpendicular to the axis at O'1 there is a circular disk of confusion of radius O'1R, and in a parallel plane at O'2 another one of radius O'2R2; between these two is situated the disk of least confusion. The largest opening of
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#17328009846806916-616: The new achromats, and were employed by P. Rudolph in the first anastigmats (photographic objectives). Canon EF lens mount The EF lens mount is the standard lens mount on the Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens. Mechanically, it is a bayonet-style mount , and all communication between camera and lens takes place through electrical contacts; there are no mechanical levers or plungers. The mount
7049-500: The object space is reproduced in an image space. The introduction of simple auxiliary terms, due to Gauss , named the focal lengths and focal planes , permits the determination of the image of any object for any system. The Gaussian theory, however, is only true so long as the angles made by all rays with the optical axis (the symmetrical axis of the system) are infinitely small, i.e., with infinitesimal objects, images and lenses; in practice these conditions may not be realized, and
7182-531: The vignetting , blur , light leaks , and other distortions of their inexpensive lenses for artistic effect to take award-winning pictures. Toy camera photography has been widely exhibited at many popular art shows, such as the annual "Krappy Kamera" show at the Soho Photo Gallery in the Tribeca neighborhood of New York City. Various publications such as Popular Photography magazine have extolled
7315-436: The 200–400mm f/4L IS and 100–400mm f/4–5.6L IS II, have a third setting, Mode 3. Mode 1 is normal mode, used for typical photography, where the subject does not move. Mode 2 is used for panning; this is useful for sports or wildlife photography, where the subject moves constantly and one will need to pan. Mode 3, intended to track action, is similar to Mode 2 in that it ignores panning; however, it only applies stabilization when
7448-478: The EF 400 mm f / 4 DO IS USM, its updated Mark II version, and the EF 70–300 mm f / 4.5–5.6 DO IS USM contain DO elements. DO lenses have a green ring on the barrel. Top range Canon EF lenses are designated "L-series", or "Luxury" lenses. L series lenses are compatible with the full range of EF or EF-S mounts and, as they are aimed at the high-end user, most also include environmental or weather sealing and
7581-530: The EOS electronics—except Zeiss, which does not have the rights to use the autofocus or the electronic aperture control of EOS cameras . The use of these third-party lenses is not supported by Canon. Sometimes compatibility problems arise, as no third party has access to Canon's specifications for camera-to-body communication. These compatibility issues mostly occur when using a newer body with an older third-party lens. Over time, most of these issues have been resolved by
7714-619: The Smartphone Film Scanner; and several lenses such as the Daguerreotype Achromat lens collection for analogue and digital SLR cameras with Canon EF , Nikon F or Pentax K mounts, inspired by 19th century Daguerreotype photography. In 2013, together with Zenit, Lomography produced a new version of the Petzval Lens designed to work with Canon EF and Nikon F mount SLR cameras. Some have questioned
7847-419: The aberration increases with the distance of the ray from the center of the lens, the aberration increases as the lens diameter increases (or, correspondingly, with the diameter of the aperture), and hence can be minimized by reducing the aperture, at the cost of also reducing the amount of light reaching the image plane. A point O (fig. 2) at a finite distance from the axis (or with an infinitely distant object,
7980-410: The aberrations belonging to ξ, η and x, y, and are functions of these magnitudes which, when expanded in series, contain only odd powers, for the same reasons as given above. On account of the aberrations of all rays which pass through O, a patch of light, depending in size on the lowest powers of ξ, η, x, y which the aberrations contain, will be formed in the plane I'. These degrees, named by J. Petzval
8113-406: The additional setting usually being near focus range (from minimum focus distance to halfway point of focus range). Longer focal length lenses and macro lenses have a relatively long travel distance for the focusing mechanism inside the lens; this feature shortens the autofocus time. When the photographer knows they will not need a certain part of the focus distance range, limiting it will help shorten
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#17328009846808246-423: The aperture stop and the object O, projects an image of the diaphragm, termed by Abbe the entrance pupil ; the exit pupil is the image formed by the component S2, which is placed behind the aperture stop. All rays which issue from O and pass through the aperture stop also pass through the entrance and exit pupils, since these are images of the aperture stop. Since the maximum aperture of the pencils issuing from O
8379-435: The autofocus time, and possibly prevent "focus hunting". Soft focus ring: This ring is found only on the 135 mm 'Soft Focus' prime lens, and enables a variable soft focus effect from completely sharp (0) to very soft (2), although it has little effect when used with apertures over f/5.6. Although the ring can be set to any position, two 'stops' are implemented at positions 1 and 2. Image stabilizer switch: This switch
8512-470: The axis (u* or h* may not be much smaller than the largest aperture U or H to be used in the system). The rays with an angle of aperture smaller than u* would not have the same distance of intersection and the same sine ratio; these deviations are called zones, and the constructor endeavors to reduce these to a minimum. The same holds for the errors depending upon the angle of the field of view, w: astigmatism, curvature of field and distortion are eliminated for
8645-846: The camera body, and each FD lens provided a breech-lock receptacle to register and fasten the lens to the bayonet. The EF mount reverses this logic, providing the bayonet on each lens, and a receptacle on the camera body. When the EF mount was introduced in 1987, it had the largest mount diameter (54 mm internal) among all 35 mm SLR cameras. The EF series includes over eighty lenses, encompassing focal lengths from 8 to 1200 mm. Many EF lenses include such features as Canon's ultrasonic motor (USM) drive, an image stabilization system (IS), diffractive optics (DO) and, particularly for L-series lenses, fluorite and aspherical lens elements. Its large diameter and relatively short flange focal distance of 44.0 mm allows mechanical adaptation of EF camera bodies to many types of non-EF lenses. It
8778-403: The conditions are maintained that any one constant of reproduction is equal for two different colors, i.e. this constant is achromatized. For example, it is possible, with one thick lens in air, to achromatize the position of a focal plane of the magnitude of the focal length. If all three constants of reproduction be achromatized, then the Gaussian image for all distances of objects is the same for
8911-417: The construction of an achromatic collective lens ( f {\displaystyle f} positive) it follows, by means of equation (4), that a collective lens I. of crown glass and a dispersive lens II. of flint glass must be chosen; the latter, although the weaker, corrects the other chromatically by its greater dispersive power. For an achromatic dispersive lens the converse must be adopted. This is, at
9044-418: The correct view from a false conception of the achromatism of the eye; this was determined by Chester More Hall in 1728, Klingenstierna in 1754 and by Dollond in 1757, who constructed the celebrated achromatic telescopes. (See telescope .) Glass with weaker dispersive power (greater v {\displaystyle v} ) is named crown glass ; that with greater dispersive power, flint glass . For
9177-488: The corresponding axes parallel, then by changing the signs of ξ, η, x, y, the values ξ', η', x', y' must likewise change their sign, but retain their arithmetical values; this means that the series are restricted to odd powers of the unmarked variables. The nature of the reproduction consists in the rays proceeding from a point O being united in another point O'; in general, this will not be the case, for ξ', η' vary if ξ, η be constant, but x, y variable. It may be assumed that
9310-566: The crown glass must have the greater refractive index for astigmatic and plane images. In all earlier kinds of glass, however, the dispersive power increased with the refractive index; that is, v {\displaystyle v} decreased as n {\displaystyle n} increased; but some of the Jena glasses by E. Abbe and O. Schott were crown glasses of high refractive index, and achromatic systems from such crown glasses, with flint glasses of lower refractive index, are called
9443-447: The deterioration of the image is proportional to the ratio of the aperture to the focal length, i.e. the relative aperture. (This explains the gigantic focal lengths in vogue before the discovery of achromatism.) Examples: Newton failed to perceive the existence of media of different dispersive powers required by achromatism; consequently he constructed large reflectors instead of refractors. James Gregory and Leonhard Euler arrived at
9576-443: The diaphragm in the ratio of their size, and presenting the same curvature to it (hemisymmetrical objectives); in these systems tan w' / tan w = 1. The constancy of a'/a necessary for this relation to hold was pointed out by R. H. Bow (Brit. Journ. Photog., 1861), and Thomas Sutton (Photographic Notes, 1862); it has been treated by O. Lummer and by M. von Rohr (Zeit. f. Instrumentenk., 1897, 17, and 1898, 18, p. 4). It requires
9709-417: The distances of intersection, of magnifications, and of monochromatic aberrations. If mixed light be employed (e.g. white light) all these images are formed and they cause a confusion, named chromatic aberration; for instance, instead of a white margin on a dark background, there is perceived a colored margin, or narrow spectrum. The absence of this error is termed achromatism, and an optical system so corrected
9842-404: The entrance pupil, i.e. the plane II. Similarly the corresponding image ray may be defined by the points (ξ', η'), and (x', y'), in the planes I' and II'. The origins of these four plane coordinate systems may be collinear with the axis of the optical system; and the corresponding axes may be parallel. Each of the four coordinates ξ', η', x', y' are functions of ξ, η, x, y; and if it be assumed that
9975-404: The exit pupil after the last refraction. From this it follows that correctness of drawing depends solely upon the principal rays; and is independent of the sharpness or curvature of the image field. Referring to fig. 4, we have O'Q'/OQ = a' tan w'/a tan w = 1/N, where N is the scale or magnification of the image. For N to be constant for all values of w, a' tan w'/a tan w must also be constant. If
10108-406: The field of view and the aperture be infinitely small, then ξ, η, x, y are of the same order of infinitesimals; consequently by expanding ξ', η', x', y' in ascending powers of ξ, η, x, y, series are obtained in which it is only necessary to consider the lowest powers. It is readily seen that if the optical system be symmetrical, the origins of the coordinate systems collinear with the optical axis and
10241-475: The field, if the collective lens has a greater refractive index (this follows from the Petzval equation; see L. Seidel, Astr. Nachr., 1856, p. 289). Should the cemented system be positive, then the more powerful lens must be positive; and, according to (4), to the greater power belongs the weaker dispersive power (greater v {\displaystyle v} ), that is to say, crown glass; consequently
10374-503: The filter. Inner, drop-in filter mounts are used on super telephoto EF lenses. They are attached by first pressing the two buttons on the filter mount, and pulling it out. Then either a round threaded filter is attached, or one can use a gelatin filter. Rear gelatin filter holders are used by cutting out a sheet of gelatin, to the size shown on the back of the lens and then sliding it into the holder. Filter mounts are useful for all types of photography, and every EF lens has either one or two of
10507-448: The focal lengths, or if the focal lengths, as ordinarily happens, be equal, by three constants of reproduction. These constants are determined by the data of the system (radii, thicknesses, distances, indices, etc., of the lenses); therefore their dependence on the refractive index, and consequently on the color, are calculable. The refractive indices for different wavelengths must be known for each kind of glass made use of. In this manner
10640-519: The focal point. Piston and tilt are not true optical aberrations, since when an otherwise perfect wavefront is altered by piston and tilt, it will still form a perfect, aberration-free image, only shifted to a different position. Chromatic aberration occurs when different wavelengths are not focussed to the same point. Types of chromatic aberration are: In a perfect optical system in the classical theory of optics , rays of light proceeding from any object point unite in an image point ; and therefore
10773-435: The geometry of the lens or mirror and occur both when light is reflected and when it is refracted. They appear even when using monochromatic light , hence the name. Chromatic aberrations are caused by dispersion , the variation of a lens's refractive index with wavelength . Because of dispersion, different wavelengths of light come to focus at different points. Chromatic aberration does not appear when monochromatic light
10906-413: The image plane of the axis point are represented as functions of the angles of the field of view. The final form of a practical system consequently rests on compromise; enlargement of the aperture results in a diminution of the available field of view, and vice versa. But the larger aperture will give the larger resolution. The following may be regarded as typical: In optical systems composed of lenses,
11039-428: The images projected by uncorrected systems are, in general, ill-defined and often blurred if the aperture or field of view exceeds certain limits. The investigations of James Clerk Maxwell and Ernst Abbe showed that the properties of these reproductions, i.e., the relative position and magnitude of the images, are not special properties of optical systems, but necessary consequences of the supposition (per Abbe) of
11172-594: The introduction of the EF 300 mm f / 2.8L USM lens in 1987. Canon was the first camera maker to successfully commercialise the USM technology. EF lenses equipped with USM drives have fast, silent and precise autofocus operations, and consume less power compared to other AF drive motors. There are three types of USMs: ring-type USM , micromotor USM , and Nano USM . Ring-type USM allows for full-time manual focus (FT-M) operations without switching out of AF mode. Micromotor USM
11305-597: The inverse method: they compose a system from certain, often quite personal experiences, and test, by the trigonometrical calculation of the paths of several rays, whether the system gives the desired reproduction (examples are given in A. Gleichen, Lehrbuch der geometrischen Optik , Leipzig and Berlin, 1902). The radii, thicknesses and distances are continually altered until the errors of the image become sufficiently small. By this method only certain errors of reproduction are investigated, especially individual members, or all, of those named above. The analytical approximation theory
11438-526: The lens (as could happen if a lens without FT-M is manually focused while in AF mode). Focusing distance range limiter switch: This switch is found on most longer focal length lenses, and macro lenses. It is used for limiting the focusing distance range of the lens when using it in autofocus mode. Most lenses have two settings; these are usually full focus range (from minimum focus distance to infinity), and distant focus range (from halfway point of focus range to infinity ). Other lenses have three settings, with
11571-411: The lens and come together at a single point in the image plane (or, more generally, the image surface ). Real lenses do not focus light exactly to a single point, however, even when they are perfectly made. These deviations from the idealized lens performance are called aberrations of the lens. Aberrations fall into two classes: monochromatic and chromatic . Monochromatic aberrations are caused by
11704-487: The lens. Only one button needs to be pressed to activate the feature. To use this button, one must first have the autofocus active, then when one wishes to halt autofocus, one presses and holds the button. To resume autofocus, one releases the button. Some newer bodies allow these buttons to be assigned to perform other functions; for instance, the Canon EOS 7D allows the photographer to set these buttons to perform any of six functions. Focus preset: The focus preset feature
11837-401: The lens. The zoom ring usually has certain, common, focal lengths marked on it. To set the zoom ring to any given focal length, one must turn the ring so that the marked focal length matches the zoom index. The zoom index is typically a white, or black, line found next to the zoom ring. Distance scale window: This feature is found on many EF lenses. This feature, while not a control or switch,
11970-703: The major third-party brands. Due to the high market penetration of EF-mount lenses, other camera manufacturers began to offer EF-mount cameras. Since the EF-mount was created for SLR cameras with their long focal flange distance, mirrorless interchangeable-lens cameras can use EF lenses with a mechanical adaptor that bridges the distance. Red Digital Cinema Company offers various camera models that can be equipped with an electronic EF-mount. Many Blackmagic Design cameras are sold in EF-mount variants. For Sony E-mount various adaptors enable using EF-mount lenses with full electronic control. Canon EF lenses typically have
12103-539: The middle of the aperture stop to be reproduced in the centers of the entrance and exit pupils without spherical aberration. M. von Rohr showed that for systems fulfilling neither the Airy nor the Bow-Sutton condition, the ratio a' cos w'/a tan w will be constant for one distance of the object. This combined condition is exactly fulfilled by holosymmetrical objectives reproducing with the scale 1, and by hemisymmetrical, if
12236-489: The numerical orders of the image, are consequently only odd powers; the condition for the formation of an image of the mth order is that in the series for Dξ' and Dη' the coefficients of the powers of the 3rd, 5th...(m-2)th degrees must vanish. The images of the Gauss theory being of the third order, the next problem is to obtain an image of 5th order, or to make the coefficients of the powers of 3rd degree zero. This necessitates
12369-401: The optimum focal plane. An extended theory that allows the calculation of the point image amplitude and intensity over a much larger volume in the focal region was recently developed ( Extended Nijboer-Zernike theory ). This Extended Nijboer-Zernike theory of point image or 'point-spread function' formation has found applications in general research on image formation, especially for systems with
12502-782: The original LOMO LC-A was discontinued. Its replacement, the LOMO LC-A+, was introduced in 2006. The new camera, made in China rather than Russia, featured the original Russian lens manufactured by LOMO PLC. This changed as of mid-2007 with the lens now made in China as well. In 2012 the LC-A+ camera was re-released as a special edition. It costs ten times the original secondhand value of the old LOMO LC-A. The Lomographic Society International (Lomography) has moved on to produce their own range of analogue cameras, films and accessories. Lomography has also released products catered to digital devices, such as
12635-411: The pencils, which take part in the reproduction of O, i.e., the angle u, is generally determined by the margin of one of the lenses or by a hole in a thin plate placed between, before, or behind the lenses of the system. This hole is termed the stop or diaphragm ; Abbe used the term aperture stop for both the hole and the limiting margin of the lens. The component S1 of the system, situated between
12768-496: The plane containing the principal ray and the axis of the system, i.e. in the first principal section or meridional section , and the other at right angles to it, i.e. in the second principal section or sagittal section. We receive, therefore, in no single intercepting plane behind the system, as, for example, a focusing screen, an image of the object point; on the other hand, in each of two planes lines O' and O" are separately formed (in neighboring planes ellipses are formed), and in
12901-411: The planes I' and II' are drawn where the images of the planes I and II are formed by rays near the axis by the ordinary Gaussian rules; and by an extension of these rules, not, however, corresponding to reality, the Gauss image point O' 0 , with coordinates ξ' 0 , η' 0 , of the point O at some distance from the axis could be constructed. Writing Dξ'=ξ'-ξ' 0 and Dη'=η'-η' 0 , then Dξ' and Dη' are
13034-513: The point O. If the object point O is infinitely distant, u1 and u2 are to be replaced by h1 and h2, the perpendicular heights of incidence; the sine condition then becomes sin u'1/h1=sin u'2/h2. A system fulfilling this condition and free from spherical aberration is called aplanatic (Greek a-, privative, plann, a wandering). This word was first used by Robert Blair to characterize a superior achromatism, and, subsequently, by many writers to denote freedom from spherical aberration as well. Since
13167-431: The point image of an aberrated optical system taking into account the effects of diffraction . The perfect point image in the presence of diffraction had already been described by Airy , as early as 1835. It took almost hundred years to arrive at a comprehensive theory and modeling of the point image of aberrated systems (Zernike and Nijboer). The analysis by Nijboer and Zernike describes the intensity distribution close to
13300-462: The position, magnitude and errors of the image depend upon the refractive indices of the glass employed (see Lens (optics) and Monochromatic aberration , above). Since the index of refraction varies with the color or wavelength of the light (see dispersion ), it follows that a system of lenses (uncorrected) projects images of different colors in somewhat different places and sizes and with different aberrations; i.e. there are chromatic differences of
13433-477: The present day, the ordinary type, e.g., of telescope objective; the values of the four radii must satisfy the equations (2) and (4). Two other conditions may also be postulated: one is always the elimination of the aberration on the axis; the second either the Herschel or Fraunhofer Condition, the latter being the best vide supra, Monochromatic Aberration ). In practice, however, it is often more useful to avoid
13566-399: The pricing of Lomography's plastic "toy" cameras, which run from $ 100 to $ 400 US. Cameras that have been marketed by Lomography: The company produces 35 mm , 120 and 110 film in color negative, black and white as well as redscale . Lomography also produces its own range of experimental color-shifting film called LomoChrome. Optical aberration In optics , aberration
13699-481: The pupil with 0 ≤ ϕ ≤ 2 π {\displaystyle 0\leq \phi \leq 2\pi } , and the fitting coefficients a 0 , … , a 8 {\displaystyle a_{0},\ldots ,a_{8}} are the wavefront errors in wavelengths. As in Fourier synthesis using sines and cosines , a wavefront may be perfectly represented by
13832-452: The quality of observed celestial objects. Understanding and correcting these optical imperfections are crucial for astronomers to achieve clear and accurate observations. Aberration can be analyzed with the techniques of geometrical optics . The articles on reflection , refraction and caustics discuss the general features of reflected and refracted rays . With an ideal lens , light from any given point on an object would pass through
13965-437: The ratio a'/a be sufficiently constant, as is often the case, the above relation reduces to the condition of Airy , i.e. tan w'/ tan w= a constant. This simple relation (see Camb. Phil. Trans., 1830, 3, p. 1) is fulfilled in all systems which are symmetrical with respect to their diaphragm (briefly named symmetrical or holosymmetrical objectives ), or which consist of two like, but different-sized, components, placed from
14098-411: The ray passing through the middle of the stop. This assumption is justified if a poor image on the focusing screen remains stationary when the aperture is diminished; in practice, this generally occurs. This ray, named by Abbe a principal ray (not to be confused with the principal rays of the Gaussian theory), passes through the center of the entrance pupil before the first refraction, and the center of
14231-402: The refracting or reflecting surface at right angles; therefore it is astigmatic (Gr. a-, privative, stigmia, a point). Naming the central ray passing through the entrance pupil the axis of the pencil or principal ray, it can be said: the rays of the pencil intersect, not in one point, but in two focal lines, which can be assumed to be at right angles to the principal ray; of these, one lies in
14364-500: The reproduction of all points of a space in image points, and are independent of the manner in which the reproduction is effected. These authors showed, however, that no optical system can justify these suppositions, since they are contradictory to the fundamental laws of reflection and refraction. Consequently, the Gaussian theory only supplies a convenient method of approximating reality; realistic optical systems fall short of this unattainable ideal. Currently, all that can be accomplished
14497-469: The reverse is not true: Lenses for the earlier Canon FD lens mount are not usable for general photography on an EF mount cameras, unless adapters with optical elements are used because they are made for a flange focal distance of only 42.0 mm. Infinity focus would be lost with an adapter which lacks optical elements. The Canon FD-EOS adapter is rare and is only usable with certain FD telephoto lenses. With
14630-480: The satisfying of five equations; in other words, there are five alterations of the 3rd order, the vanishing of which produces an image of the 5th order. The expression for these coefficients in terms of the constants of the optical system, i.e. the radii, thicknesses, refractive indices and distances between the lenses, was solved by L. Seidel ; in 1840, J. Petzval constructed his portrait objective, from similar calculations which have never been published. The theory
14763-409: The scale of reproduction be equal to the ratio of the sizes of the two components. Circular wavefront profiles associated with aberrations may be mathematically modeled using Zernike polynomials . Developed by Frits Zernike in the 1930s, Zernike's polynomials are orthogonal over a circle of unit radius. A complex, aberrated wavefront profile may be curve-fitted with Zernike polynomials to yield
14896-410: The second condition by making the lenses have contact, i.e. equal radii. According to P. Rudolph (Eder's Jahrb. f. Photog., 1891, 5, p. 225; 1893, 7, p. 221), cemented objectives of thin lenses permit the elimination of spherical aberration on the axis, if, as above, the collective lens has a smaller refractive index; on the other hand, they permit the elimination of astigmatism and curvature of
15029-477: The second. Systems in which the two astigmatic surfaces coincide are termed anastigmatic or stigmatic. Sir Isaac Newton was probably the discoverer of astigmation; the position of the astigmatic image lines was determined by Thomas Young; and the theory was developed by Allvar Gullstrand . A bibliography by P. Culmann is given in Moritz von Rohr's Die Bilderzeugung in optischen Instrumenten . By opening
15162-399: The shortest proof of the practical (Seidel) formulae. A. Gullstrand (vide supra, and Ann. d. Phys., 1905, 18, p. 941) founded his theory of aberrations on the differential geometry of surfaces. The aberrations of the third order are: (1) aberration of the axis point; (2) aberration of points whose distance from the axis is very small, less than of the third order — the deviation from
15295-545: The shutter is released—the viewfinder image is not stabilized. One should not use Mode 1 for panning as this will typically cause blurred photographs; the image stabilizer will attempt to correct for all motion, including the panning motion, but cannot do so due to the limited range of motion of the IS mechanism. Older lenses that have an image stabilizer, but do not feature this switch, are permanently in Mode 1. Some newer lenses, such as
15428-585: The sine condition and coma here fall together in one class; (3) astigmatism; (4) curvature of the field; (5) distortion. The classical imaging problem is to reproduce perfectly a finite plane (the object) onto another plane (the image) through a finite aperture. It is impossible to do so perfectly for more than one such pair of planes (this was proven with increasing generality by Maxwell in 1858, by Bruns in 1895, and by Carathéodory in 1926, see summary in Walther, A., J. Opt. Soc. Am. A 6 , 415–422 (1989)). For
15561-488: The sole distributor of all LOMO LC-A cameras outside of the former Soviet Union . The new company reached an agreement with the deputy mayor of St Petersburg, the future Russian Prime Minister and President, Vladimir Putin , to receive a tax break in order to keep the LOMO factory in the city open. Since the introduction of the original LOMO LC-A, Lomography has produced a line of their own film cameras. In 2005, production of
15694-610: The specific IS in the lens. Canon has released several versions of the IS system, including the following: All EF lenses that support IS have the words "Image Stabilizer" written on the lens. On some of Canon's larger telephoto lenses, the words "Image Stabilizer" are etched onto a metal plate affixed to the lens. Diffractive optics (DO) are special lens elements that are used in some lenses. DO lenses are usually smaller and lighter and are better at handling chromatic aberration , compared to conventional lenses of similar focal length and aperture value. They are more expensive to make. Only
15827-411: The stop wider, similar deviations arise for lateral points as have been already discussed for axial points; but in this case they are much more complicated. The course of the rays in the meridional section is no longer symmetrical to the principal ray of the pencil; and on an intercepting plane there appears, instead of a luminous point, a patch of light, not symmetrical about a point, and often exhibiting
15960-408: The system are parallel, and their intersections, after traversing the system, vary according to their perpendicular height of incidence, i.e. their distance from the axis. This distance replaces the angle u in the preceding considerations; and the aperture, i.e., the radius of the entrance pupil, is its maximum value. If rays issuing from O (fig. 1) are concurrent, it does not follow that points in
16093-407: The three types used. Lens hood mount: This feature is found on most EF lenses. This mount is used for attaching the lens hood . The hood mount is of a bayonet style on most EF lenses, though a clip-on style hood mount is used for a small selection of current lenses. Tripod collar: This feature is found on most longer focal length lenses, and macro lenses. The tripod collar is used for attaching
16226-465: The tripod ring matches the index mark on the distance scale. The tripod ring is used for attaching a tripod/monopod near to the point of balance of the lens-body combination, more conveniently than the camera body. In the case of larger and heavier lenses, there is also less strain on the lens mount if the body is supported by the tripod-mounted lens than if the lens were to be supported by a tripod-mounted body. Ultrasonic motor (USM) lenses appeared with
16359-409: The tripod ring. There are two main styles of tripod rings. One type is opened up, placed on the lens' tripod collar, then closed and tightened. The other type does not open, but instead is slid up the lens from the mount end (which can only be done when the lens is not mounted on a camera body) and tightened. To set the tripod ring so that it is level with the lens, rotate the ring until the index mark on
16492-426: The two colors, and the system is said to be in stable achromatism. In practice it is more advantageous (after Abbe) to determine the chromatic aberration (for instance, that of the distance of intersection) for a fixed position of the object, and express it by a sum in which each component conlins the amount due to each refracting surface. In a plane containing the image point of one color, another colour produces
16625-430: The unpredictable, non-standard optical traits of toy cameras (such as light leaks and irregular lens alignment), and non-standard film processing techniques for aesthetic effect. Similar-looking techniques with digital photography, often involving "lomo" image filters in post-processing, may also be considered Lomographic. While cheap plastic toy cameras using film were and are produced by multiple manufacturers, Lomography
16758-531: The virtues of the Diana camera in its own right as an "art" producing image maker. Several books have also featured the work of toy cameras such as The Friends of Photography's The Diana Show, Iowa by Nancy Rexroth , and Angels at the Arno by Eric Lindbloom. Lomography is a photographic style which involves taking spontaneous photographs with minimal attention to technical details. Lomographic images often exploit
16891-536: Was elaborated by S. Finterswalder, who also published a posthumous paper of Seidel containing a short view of his work; a simpler form was given by A. Kerber. A. Konig and M. von Rohr have represented Kerber's method, and have deduced the Seidel formulae from geometrical considerations based on the Abbe method, and have interpreted the analytical results geometrically. The aberrations can also be expressed by means of
17024-450: Was first introduced in 1987. Canon claims to have produced its 100-millionth EF-series interchangeable lens on April 22, 2014. The EF mount replaces its predecessor, the FD mount . The standard autofocus lens mounting technology of the time used a motor in the camera body to drive the mechanics of the focus helicoid in the lens by using a transfer lever. The key innovation of the EF series
17157-691: Was founded in 1992 by a group of Viennese students interested in the LC-A, a camera created by LOMO PLC of Saint Petersburg, Russia. Lomography started as an art movement through which the students put on exhibitions of photos; the art movement then developed into the Lomographische AG, a commercial enterprise. Lomography is a commercial company headquartered in Vienna, Austria, which sells cameras, accessories, and film. Lomography signed an exclusive distribution agreement with LOMO PLC in 1995 — becoming
17290-443: Was pursued by Clerk Maxwell ( Proc. London Math. Soc., 1874–1875; (see also the treatises of R. S. Heath and L. A. Herman), M. Thiesen ( Berlin. Akad. Sitzber., 1890, 35, p. 804), H. Bruns ( Leipzig. Math. Phys. Ber., 1895, 21, p. 410), and particularly successfully by K. Schwarzschild ( Göttingen. Akad. Abhandl., 1905, 4, No. 1), who thus discovered the aberrations of the 5th order (of which there are nine), and possibly
17423-404: Was the Canon EF 400mm f/4 DO IS USM. Canon in 2008 created the first lens with SWC technology (Subwavelength Structure Coating). That lens was the Canon EF 24mm f/1.4L II USM. Canon in 2009 created the first lens with Hybrid IS (Image Stabilization) which compensates both angle camera shake and shift camera shake with the Canon EF 100mm f/2.8L Macro IS USM. Canon in 2010 was the first to create
17556-473: Was the first to create an interchangeable 10× superzoom lens for SLR cameras. That lens was Canon EF 35-350mm f/3.5-5.6L USM. In 1993 Canon created the first Super UD (Ultra low Dispersion) lens with the Canon EF 400mm f/5.6L USM. In 1995 Canon created the first lens with IS (Image Stabilization). That lens was the Canon EF 75-300mm f/4-5.6 IS USM. Canon in 2001 was the first to create a lens with DO (multi layered Diffractive Optical element) element. That lens
17689-426: Was to use a motor inside the lens itself for focusing. This allowed for autofocusing lenses which did not require mechanical levers in the mount mechanism, only electrical contacts to supply power and instructions to the lens motor. The motors were designed for the particular lens they were installed in. The EF mount reversed the mechanical logic of the FD mount. The FD mount provided the three-eared bayonet fitting on
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