Misplaced Pages

#947052

93-500: The SLX was discontinued shortly after the Rolleiflex 6006 was released in 1984. After the introduction of the all-mechanical SL66 in 1966, Rollei began designing a successor which would incorporate electronics to enable contemporary features from small-format photography, including autoexposure and motorized film transport. The prototypes initially were designated SLC66 , then SLX66 , and finally were revealed at photokina '74 as

186-574: A Polaroid back was available The SLX uses conventional helicoids for focusing instead of the extending focusing bellows on the camera body of the SL66. In addition, SLX lenses all are equipped with in-lens leaf shutters . Because of this, SLX and SL66 lenses are not compatible. A 10-pin interface is provided to transmit signals between the lens and camera body. The leaf shutter and aperture leaves are driven by voice coil motors , which Rollei called "linear motors". The aperture control ring on each lens has

279-489: A centre-weighted average metering pattern; compared to the SLX, these cameras add an off-the-film sensor for TTL flash metering. The 6008 and 6003 add aperture-priority and program autoexposure modes; in addition, the metering pattern can be switched between centre-weighted multi-zone and spot, covering approximately 1% of the overall image area. A multi-spot metering pattern was added to later 6008/6003 cameras. The 6001 drops

372-432: A constant light (from a fixed lens), one flash per minute (from a rotating lens with eight panels), and two per minute (16 panels). In late 1825, to reduce the loss of light in the reflecting elements, Fresnel proposed to replace each mirror with a catadioptric prism, through which the light would travel by refraction through the first surface, then total internal reflection off the second surface, then refraction through

465-414: A conventional lens by dividing the lens into a set of concentric annular sections. An ideal Fresnel lens would have an infinite number of sections. In each section, the overall thickness is decreased compared to an equivalent simple lens. This effectively divides the continuous surface of a standard lens into a set of surfaces of the same curvature, with stepwise discontinuities between them. In some lenses,

558-455: A cylindrical form while retaining the property of reflecting light from a single point back to that point. Reflectors of this form, paradoxically called "dioptric mirrors", proved particularly useful for returning light from the landward side of the lamp to the seaward side. As lighthouses proliferated, they became harder to distinguish from each other, leading to the use of colored filters, which wasted light. In 1884, John Hopkinson eliminated

651-449: A depth-of-field preview button (stop-down) are next to the main switch. The opposite side of the camera has a strap lug, hotshoe, and a slot to accommodate the rechargeable NiCd battery; advertised stamina is 1000 exposures per charge. It measures 75×30×36 mm (3.0×1.2×1.4 in) (LWH) and operates at 9.6 V with a capacity of 450 mA-hr. The battery has an integrated 20 mm cartridge fuse (0.8 A / 250 V) to protect

744-402: A detachable film back which accommodated the same film inserts as the 6002; the 6003 back also could be removed completely and fitted with the 6006/6008 film magazines. The Rollei Digital ScanPack is a back with a scanning linear image sensor which was available for the 6000 System cameras. It was tethered to a computer via SCSI . The image recorded was 41.2×35 mm (1.62×1.38 in) with

837-401: A focal length of 920 mm ( 36 + 1 ⁄ 4  in) and stands about 2.59 m (8 ft 6 in) high, and 1.8 m (6 ft) wide. The smallest (sixth) order has a focal length of 150 mm (6 in) and a height of 433 mm ( 17 + 1 ⁄ 16  in). The largest Fresnel lenses are called hyperradiant (or hyper-radial). One such lens was on hand when it

930-435: A hole which is 85 mm in diameter as an adaptable interface for the lens and back; Rollei sold adapters that would accept a limited selection of 6000 System lenses, viewfinders, and backs, and additional adapters were available for backs from competing medium format systems, including Hasselblad V-system, Mamiya RB, and Horseman 6×9, or a T2 adapter for use with 135 film and digital SLRs. When using 6000 System lenses,

1023-527: A knob operated by the photographer's right hand and range from 30 to 1 ⁄ 500  sec in whole steps; cameras released after the PQS series add a faster 1 ⁄ 1000  sec speed. Since lenses are focused by helicoid extension, the traditional focusing knob on the left side of Rolleiflex SL66 and TLR cameras is not present. The 6006 uses a interchangeable film magazine with integrated dark slide to accommodate mid-roll film changes. In addition to

SECTION 10

#1732793092948

1116-548: A lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. Because of its use in lighthouses, it has been called "the invention that saved a million ships". The first person to focus a lighthouse beam using a lens was apparently the London glass-cutter Thomas Rogers, who proposed the idea to Trinity House in 1788. The first Rogers lenses, 53   cm in diameter and 14   cm thick at

1209-417: A maximum resolution of 5850×5000 pixels. The 6000 series uses lenses that are physically compatible with earlier SLX lenses. These lenses use conventional helicoids for focusing instead of the extending focusing bellows on the camera body of the SL66. In addition, SLX/6000 lenses all are equipped with in-lens leaf shutters . Because of this, SLX/6000 and SL66 lenses are not compatible. A 10-pin interface

1302-414: A metal housing, a reflector, a lamp assembly, and a Fresnel lens. Many Fresnel instruments allow the lamp to be moved relative to the lens' focal point , to increase or decrease the size of the light beam. As a result, they are very flexible, and can often produce a beam as narrow as 7° or as wide as 70°. The Fresnel lens produces a very soft-edged beam, so is often used as a wash light. A holder in front of

1395-859: A position. Perhaps the most widespread use of Fresnel lenses, for a time, occurred in automobile headlamps , where they can shape the roughly parallel beam from the parabolic reflector to meet requirements for dipped and main-beam patterns, often both in the same headlamp unit (such as the European H4 design). For reasons of economy, weight, and impact resistance, newer cars have dispensed with glass Fresnel lenses, using multifaceted reflectors with plain polycarbonate lenses. However, Fresnel lenses continue in wide use in automobile tail, marker, and reversing lights. Glass Fresnel lenses also are used in lighting instruments for theatre and motion pictures (see Fresnel lantern ); such instruments are often called simply Fresnels . The entire instrument consists of

1488-399: A replacement for the SLX, with a non-interchangeable back; the 6008/6003 are positioned similarly. Rollei released numerous sub-variants of each model. Broadly, the 6000 System can be divided into two distinct generations: the 6006/6002, which bear some similarities to the preceding SLX, and the 6008/6003/6001, which introduced upgraded metering and shutters. Like the preceding SLX, the 6006

1581-486: A rotating array outside the fixed array. Each panel of the rotating array was to refract part of the fixed light from a horizontal fan into a narrow beam. Also in 1825, Fresnel unveiled the Carte des Phares ('lighthouse map'), calling for a system of 51 lighthouses plus smaller harbor lights, in a hierarchy of lens sizes called "orders" (the first being the largest), with different characteristics to facilitate recognition:

1674-428: A selectable interval between 0.1 and 1.5 seconds. It was supplied with a 2 m (6 ft 7 in) cable as standard, and a 10 m (33 ft) cable was available as an accessory. Fresnel lens A Fresnel lens ( / ˈ f r eɪ n ɛ l , - n əl / FRAY -nel, -⁠nəl ; / ˈ f r ɛ n ɛ l , - əl / FREN -el, -⁠əl ; or / f r eɪ ˈ n ɛ l / fray- NEL )

1767-516: A separate setting at "A", which puts the camera into shutter-priority autoexposure. Extension tubes and a bellows unit were available for close-up work. As standard equipment, the SLX comes with a folding waist-level finder with a built-in magnifier and a ground glass focusing screen with a central split-image rangefinder spot surrounded by a microprism collar, grid lines etched at regular intervals, and an integrated Fresnel lens . The viewfinder displays an image 55×55 mm (2.2×2.2 in), which

1860-557: A substantial reduction in thickness (and thus mass and volume of material) at the expense of reducing the imaging quality of the lens, which is why precise imaging applications such as photography usually still use larger conventional lenses. Fresnel lenses are usually made of glass or plastic; their size varies from large (old historical lighthouses, meter size) to medium (book-reading aids, OHP viewgraph projectors) to small ( TLR / SLR camera screens, micro-optics). In many cases they are very thin and flat, almost flexible, with thicknesses in

1953-608: A system similar to Condorcet's in 1811, and by 1820 was advocating its use in British lighthouses. The French Commission des Phares  [ FR ] (Commission of Lighthouses) was established by Napoleon in 1811, and placed under the authority of French physicist Augustin-Jean Fresnel 's employer, the Corps of Bridges and Roads. As the members of the commission were otherwise occupied, it achieved little in its early years. However, on 21 June 1819—three months after winning

SECTION 20

#1732793092948

2046-513: A way to remove defects by reheating and remolding the glass. Arago assisted Fresnel with the design of a modified Argand lamp with concentric wicks (a concept that Fresnel attributed to Count Rumford ), and accidentally discovered that fish glue was heat-resistant, making it suitable for use in the lens. The prototype, finished in March 1820, had a square lens panel 55   cm on a side, containing 97 polygonal (not annular) prisms—and so impressed

2139-541: Is 93% of the area recorded on the film. The magnifying lens in the viewfinder could be changed. Other available viewfinders include: The screen could be changed to one of several alternatives, which are shared with the SL66: Rollei offered the ME-1 multi-exposure control unit for the SLX; it allows the photographer to record up to ten images on a single frame, at a selectable interval between 0.1 and 1.5 seconds. It

2232-543: Is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections. The simpler dioptric (purely refractive ) form of the lens was first proposed by Georges-Louis Leclerc, Comte de Buffon , and independently reinvented by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses . The catadioptric (combining refraction and reflection) form of

2325-446: Is now integrated into the camera body, instead of being housed in an accessory viewfinder. In addition, the SLX back is integrated into the camera and cannot be removed; film is loaded into an interchangeable holder, but these are not protected by a dark slide. The main switch falls under the photographer's right hand, and has three rotary positions for "O"ff, "S"ingle, or "C"ontinuous exposures. A 14-pin interface for remote operation and

2418-459: Is on. They attach to the passenger-side window. Another automobile application of a Fresnel lens is a rear view enhancer, as the wide view angle of a lens attached to the rear window permits examining the scene behind a vehicle, particularly a tall or bluff-tailed one, more effectively than a rear-view mirror alone. Fresnel lenses have been used on rangefinding equipment and projected map display screens. Fresnel lenses have also been used in

2511-399: Is provided to transmit signals between the lens and camera body. The leaf shutter and aperture leaves are driven by voice coil motors , which Rollei called "linear motors". The aperture control ring on each lens has a separate setting at "A", which puts the camera into shutter-priority autoexposure. Extension tubes and a bellows unit were available for close-up work. The 6000 System uses

2604-475: Is the double-flashing lens of the Point Arena Light , which was in service from 1908 to 1977. The development of hyper-radial lenses was driven in part by the need for larger light sources, such as gas lights with multiple jets, which required a longer focal length for a given beam-width, hence a larger lens to collect a given fraction of the generated light. The first hyper-radial lens was built for

2697-414: The École Polytechnique , in order to save his remaining time and energy for his lighthouse work. In the same year he designed the first fixed lens—for spreading light evenly around the horizon while minimizing waste above or below. Ideally the curved refracting surfaces would be segments of toroids about a common vertical axis, so that the dioptric panel would look like a cylindrical drum. If this

2790-478: The 1 to 5 mm ( 1 ⁄ 32 to 3 ⁄ 16  in) range. Most modern Fresnel lenses consist only of refractive elements. Lighthouse lenses, however, tend to include both refracting and reflecting elements, the latter being outside the metal rings seen in the photographs. While the inner elements are sections of refractive lenses, the outer elements are reflecting prisms, each of which performs two refractions and one total internal reflection , avoiding

2883-513: The Isle of May , Scotland, on 22 September 1836. The first large catadioptric lenses were made in 1842 for the lighthouses at Gravelines and Île Vierge , France; these were fixed third-order lenses whose catadioptric rings (made in segments) were one metre in diameter. Stevenson's first-order Skerryvore lens, lit in 1844, was only partly catadioptric; it was similar to the Cordouan lens except that

Rolleiflex SLX - Misplaced Pages Continue

2976-560: The Meta Quest Pro , have switched to a pancake lens design due to its smaller form factor and less chromatic aberration than Fresnel lenses. Multi-focal Fresnel lenses are also used as a part of retina identification cameras, where they provide multiple in- and out-of-focus images of a fixation target inside the camera. For virtually all users, at least one of the images will be in focus, thus allowing correct eye alignment. Canon and Nikon have used Fresnel lenses to reduce

3069-697: The Rolleiflex Hy6 , a hybrid medium format SLR camera which accepted both analog film backs or backs with digital sensors, using the Rolleiflex SLX/6000 lens mount. The Hy6 was developed by Jenoptik and sold simultaneously by Rollei and other brands, including Leaf (as the AFi) and Sinar (as the Hy6). The 6000 System was discontinued in 2015. Like the Rolleiflex TLR, SL66 , and SLX ,

3162-514: The Sinclair TV80 . They are also used in traffic lights . Fresnel lenses are used in left-hand-drive European lorries entering the UK and Republic of Ireland (and vice versa, right-hand-drive Irish and British trucks entering mainland Europe) to overcome the blind spots caused by the driver operating the lorry while sitting on the wrong side of the cab relative to the side of the road the car

3255-488: The transverse wave hypothesis. Shortly after the Cordouan lens was lit, Fresnel started coughing up blood. In May 1824, Fresnel was promoted to Secretary of the Commission des Phares , becoming the first member of that body to draw a salary, albeit in the concurrent role of Engineer-in-Chief. Late that year, being increasingly ill, he curtailed his fundamental research and resigned his seasonal job as an examiner at

3348-441: The 6000 series uses 120 or 220 rollfilm to produce frames of up to 6×6 cm (nominal); the actual image size is based on imperial units , measuring 2 + 1 ⁄ 4 × 2 + 1 ⁄ 4  in (57×57 mm). The camera has a modular design; the central camera body incorporates the single-lens reflex mirror and exposure controls, with interfaces accommodating interchangeable lenses, viewfinders, and focusing screens. Most of

3441-420: The 6008 integral (1995), 6003 professional (1996), and 6008 E (1997); improvements included the addition of a multi-spot metering mode and a faster motor drive. In 1998, Rollei released the 6001 professional, which was a studio-only version of the 6003 professional, dropping the ambient light meter entirely, as it was intended to be used with flash lighting. The final 6000 series cameras were released in 2002;

3534-463: The 6008 integral2 included improvements to the flash metering system, and the 6008 AF built on that by adding an autofocus system along with a new line of AF lenses. Rollei released the X-Act 2 in 2008, which is a monorail view camera with a full range of rise/fall, shift, and swing movements for both the lens (front) and film (rear) standards. The front and rear standards each are fitted with

3627-576: The Commission that Fresnel was asked for a full eight-panel version. This model, completed a year later in spite of insufficient funding, had panels 76   cm square. In a public spectacle on the evening of 13 April 1821, it was demonstrated by comparison with the most recent reflectors, which it suddenly rendered obsolete. Soon after this demonstration, Fresnel published the idea that light, including apparently unpolarized light, consists exclusively of transverse waves , and went on to consider

3720-464: The Rogers mirror of 60 years earlier, except that it subtended a whole hemisphere). Light radiated into the forward hemisphere but missing the bull's-eye lens was deflected by the paraboloid into a parallel beam surrounding the bull's-eye lens, while light radiated into the backward hemisphere was reflected back through the lamp by the spherical reflector (as in Rogers' arrangement), to be collected by

3813-418: The SLX, but retaining the updated TTL/OTF light meter. In addition, the 6002 added multiple exposure capability, which subsequently was added with the updated 6006 in 1989. In 1988, Rollei released the 6008 professional, which eventually replaced the 6006. Externally, the 6008 moves the on/motor mode switch to a location coaxial with the shutter speed knob. An updated 6008 (branded 6008 professional SRC1000)

Rolleiflex SLX - Misplaced Pages Continue

3906-423: The SLX, the 6000 series cameras incorporate electronic autoexposure and motorized film transport , competing directly with the line of similar integrated-motor Hasselblad V-system cameras which started with the 500EL. The 6006 was followed by the 6002 (1986), 6008 (1988), 6003 (1996), 6001 (1998), and 6008 AF (2002). The 6002 may be regarded as a simplified version of the 6006, or alternatively as

3999-531: The SLX. The SLX reached retail markets in Spring 1976. Internal updates aimed to improve reliability were rolled out as an SLX Mark II in 1978 and the original SLX was discontinued in 1979. The updated cameras may be distinguished by the color of the trim plate surrounding the power/drive mode dial and 14-pin DIN interface on the right side of the camera. On the original SLX, this is an unpainted aluminum plate, while on

4092-467: The Stevensons in 1885 by F. Barbier & Cie of France, and tested at South Foreland Lighthouse with various light sources. Chance Brothers (Hopkinson's employers) then began constructing hyper-radials, installing their first at Bishop Rock Lighthouse in 1887. In the same year, Barbier installed a hyper-radial at Tory Island . But only about 30 hyper-radials went into service before

4185-527: The United States by the 1870s. In 1858 the company produced "a very small number of pressed flint-glass sixth-order lenses" for use in lighthouses—the first Fresnel lighthouse lenses made in America. By the 1950s, the substitution of plastic for glass made it economic to use Fresnel lenses as condensers in overhead projectors. The Fresnel lens reduces the amount of material required compared to

4278-438: The accessories for the SLX may be interchanged with the SL66, including the focusing screens. With the standard (80 mm) lens and folding waist-level finder, the SLX measures 153×138×85 mm (6.0×5.4×3.3 in) (L×H×W) and weighs 1.8 kg (4.0 lb). Compared to the SL66, the SLX adds shutter-priority autoexposure capability and drops the manual crank for motorized film advance and shutter charging. The light meter

4371-557: The actors and the camera, distorting the scale and composition of the scene to humorous effect. The Pixar movie Wall-E features a Fresnel lens in the scenes where the protagonist watches the musical Hello, Dolly! magnified on an iPod . Virtual reality headsets, such as the Meta Quest 2 and the HTC Vive Pro use Fresnel lenses, as they allow a thinner and lighter form factor than regular lenses. Newer devices, such as

4464-440: The ambient light meter entirely, but supports TTL OTF flash metering. The main switch falls under the photographer's right hand on the 6006/6002, and has three rotary positions for "O"ff, "S"ingle, or "C"ontinuous exposures. A 14-pin interface for remote operation and a depth-of-field preview button (stop-down) are next to the main switch. For the 6008 and later cameras, the main switch and depth-of-field preview have been moved to

4557-471: The area recorded on the film. The magnifying lens in the viewfinder could be changed. Other available viewfinders include: The screen could be changed to one of several alternatives, which are shared with the SL66: Rollei offered the ME-1 multi-exposure control unit using the 14-pin DIN connector first released with the SLX; it allows the photographer to record up to ten images on a single frame, at

4650-421: The cameras accommodate interchangeable film backs. Nearly all of the accessories and components for the SLX could be used with the 6006, aside from the back and body. Like the SLX, all 6000 System cameras have manual ambient light metering and shutter-priority autoexposure capability, along with motorized film advance and shutter charging. The light meter is integrated into the camera body. The 6006 and 6002 have

4743-510: The center, were installed at the Old Lower Lighthouse at Portland Bill in 1789. Behind each lamp was a back-coated spherical glass mirror, which reflected rear radiation back through the lamp and into the lens. Further samples were installed at Howth Baily , North Foreland , and at least four other locations by 1804. But much of the light was wasted by absorption in the glass. In 1748, Georges-Louis Leclerc, Comte de Buffon

SECTION 50

#1732793092948

4836-405: The center. The result was an all-glass holophote, with no losses from metallic reflections. James Timmins Chance modified Thomas Stevenson's all-glass holophotal design by arranging the double-reflecting prisms about a vertical axis. The prototype was shown at the 1862 International Exhibition in London. Later, to ease manufacturing, Chance divided the prisms into segments, and arranged them in

4929-512: The completion of Augustin Fresnel's original Carte des Phares . Thomas Stevenson (younger brother of Alan) went a step beyond Fresnel with his "holophotal" lens, which focused the light radiated by the lamp in nearly all directions, forward or backward, into a single beam. The first version, described in 1849, consisted of a standard Fresnel bull's-eye lens, a paraboloidal reflector, and a rear hemispherical reflector (functionally equivalent to

5022-631: The curved surfaces are replaced with flat surfaces, with a different angle in each section. Such a lens can be regarded as an array of prisms arranged in a circular fashion with steeper prisms on the edges and a flat or slightly convex center. In the first (and largest) Fresnel lenses, each section was actually a separate prism. 'Single-piece' Fresnel lenses were later produced, being used for automobile headlamps, brake, parking, and turn signal lenses, and so on. In modern times, computer-controlled milling equipment (CNC) or 3-D printers might be used to manufacture more complex lenses. Fresnel lens design allows

5115-428: The depth of the 6006, compared to the SLX. A second version of the 6006 was released in 1989 with minor updates. Externally, the mechanical cable release socket was removed; on the original 6006, this was centered on the bottom front of the body between the two microswitch shutter releases. The 6006 was supplemented by the 6002 (1986), which was a simplified 6006, reverting back to the interchangeable film magazines of

5208-549: The development of more compact bright lamps rendered such large optics unnecessary (see Hyperradiant Fresnel lens ). Production of one-piece stepped dioptric lenses—roughly as envisaged by Buffon—became feasible in 1852, when John L. Gilliland of the Brooklyn Flint-Glass Company patented a method of making lenses from pressed and molded glass. The company made small bull's-eye lenses for use on railroads, steamboats, and docks; such lenses were common in

5301-475: The exact date on which Fresnel formally recommended lentilles à échelons is unknown. Much to Fresnel's embarrassment, one of the assembled commissioners, Jacques Charles , recalled Buffon's suggestion. However, whereas Buffon's version was biconvex and in one piece, Fresnel's was plano-convex and made of multiple prisms for easier construction. With an official budget of 500 francs, Fresnel approached three manufacturers. The third, François Soleil, found

5394-572: The field of popular entertainment. The British rock artist Peter Gabriel made use of them in his early solo live performances to magnify the size of his head, in contrast to the rest of his body, for dramatic and comic effect. In the Terry Gilliam film Brazil , plastic Fresnel screens appear ostensibly as magnifiers for the small CRT monitors used throughout the offices of the Ministry of Information. However, they occasionally appear between

5487-417: The film transport motor from overcurrent in case of a jammed mechanism. Two separate shutter releases are provided on the bottom front corners of the camera, which may be operated by the photographer's right or left hand. Shutter speeds are selected by a knob operated by the photographer's right hand and range from 30 to 1 ⁄ 500  sec in whole steps. Since lenses are focused by helicoid extension,

5580-478: The forward components. The first unit was installed at North Harbour, Peterhead , in August 1849. Stevenson called this version a "catadioptric holophote", although each of its elements was either purely reflective or purely refractive. In the second version of the holophote concept, the bull's-eye lens and paraboloidal reflector were replaced by a catadioptric Fresnel lens—as conceived by Fresnel, but expanded to cover

5673-481: The handheld LensControl S was used to control shutter speed and aperture. The X-Act also was designed to accept large format lenses for maximum image coverage and movement flexibility; Rollei also sold its own leaf shutter units, branded ElectronicShutter, for use with lenses with size 0 or size 1 shutters. The ElectronicShutter units also were controlled using the LensControl S. In 2007, Rollei began selling

SECTION 60

#1732793092948

5766-433: The implications for double refraction and partial reflection. Fresnel acknowledged the British lenses and Buffon's invention in a memoir read on 29 July 1822 and printed in the same year. The date of that memoir may be the source of the claim that Fresnel's lighthouse advocacy began two years later than Brewster's; but the text makes it clear that Fresnel's involvement began no later than 1819. Fresnel's next lens

5859-502: The lens can hold a colored plastic film ( gel ) to tint the light or wire screens or frosted plastic to diffuse it. The Fresnel lens is useful in the making of motion pictures not only because of its ability to focus the beam brighter than a typical lens, but also because the light is a relatively consistent intensity across the entire width of the beam of light. Aircraft carriers and naval air stations typically use Fresnel lenses in their optical landing systems . The "meatball" light aids

5952-403: The lens, entirely invented by Fresnel, has outer prismatic elements that use total internal reflection as well as refraction to capture more oblique light from the light source and add it to the beam, making it visible at greater distances. The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by

6045-468: The light loss that occurs in reflection from a silvered mirror. Fresnel designed six sizes of lighthouse lenses, divided into four orders based on their size and focal length. The 3rd and 4th orders were sub-divided into "large" and "small". In modern use, the orders are classified as first through sixth order. An intermediate size between third and fourth order was added later, as well as sizes above first order and below sixth. A first-order lens has

6138-460: The light source. The light path through these elements can include an internal reflection , rather than the simple refraction in the planar Fresnel element. These lenses conferred many practical benefits upon the designers, builders, and users of lighthouses and their illumination. Among other things, smaller lenses could fit into more compact spaces. Greater light transmission over longer distances, and varied patterns, made it possible to triangulate

6231-555: The lower slats were replaced by French-made catadioptric prisms, while mirrors were retained at the top. The first fully catadioptric first-order lens, installed at Pointe d'Ailly in 1852, also gave eight rotating beams plus a fixed light at the bottom; but its top section had eight catadioptric panels focusing the light about 4 degrees ahead of the main beams, in order to lengthen the flashes. The first fully catadioptric lens with purely revolving beams—also of first order—was installed at Saint-Clément-des-Baleines in 1854, and marked

6324-402: The main beam, increasing the duration of the flash. Below the main panels were 128 small mirrors arranged in four rings, stacked like the slats of a louver or Venetian blind . Each ring, shaped like a frustum of a cone , reflected the light to the horizon, giving a fainter steady light between the flashes. The official test, conducted on the unfinished Arc de Triomphe on 20 August 1822,

6417-428: The middle of the 20th centuries; most lighthouses have now retired glass Fresnel lenses from service and replaced them with much less expensive and more durable aerobeacons , which themselves often contain plastic Fresnel lenses. Lighthouse Fresnel lens systems typically include extra annular prismatic elements, arrayed in faceted domes above and below the central planar Fresnel, in order to catch all light emitted from

6510-476: The need for filters by inventing the "group-flashing" lens, in which the dioptric and/or the catadioptric panels were split so as to give multiple flashes—allowing lighthouses to be identified not only by frequency of flashes, but also by multiplicity of flashes. Double-flashing lenses were installed at Tampico (Mexico) and Little Basses (Sri Lanka) in 1875, and a triple-flashing lens at Casquets Lighthouse ( Channel Islands ) in 1876. The example shown (right)

6603-423: The number of segments increases, the two types of lens become more similar to each other. In the abstract case of an infinite number of segments, the difference between curved and flat segments disappears. Imaging lenses can be classified as: Non-imaging lenses can be classified as: High-quality glass Fresnel lenses were used in lighthouses, where they were considered state of the art in the late 19th and through

6696-634: The physics Grand Prix of the Academy of Sciences for his celebrated memoir on diffraction —Fresnel was "temporarily" seconded to the commission on the recommendation of François Arago (a member since 1813), to review possible improvements in lighthouse illumination. By the end of August 1819, unaware of the Buffon-Condorcet-Brewster proposal, Fresnel made his first presentation to the commission, recommending what he called lentilles à échelons ('lenses by steps') to replace

6789-412: The pilot in maintaining proper glide slope for the landing. In the center are amber and red lights composed of Fresnel lenses. Although the lights are always on, the angle of the lens from the pilot's point of view determines the color and position of the visible light. If the lights appear above the green horizontal bar, the pilot is too high. If it is below, the pilot is too low, and if the lights are red,

6882-399: The pilot is very low. Fresnel lenses are also commonly used in searchlights , spotlights , and flashlights . Fresnel lenses are used as simple hand-held magnifiers . They are also used to correct several visual disorders, including ocular-motility disorders such as strabismus . Fresnel lenses have been used to increase the visual size of CRT displays in pocket televisions , notably

6975-431: The reflectors then in use, which reflected only about half of the incident light. Another report by Fresnel, dated 29 August 1819 (Fresnel, 1866–70, vol. 3, pp. 15–21), concerns tests on reflectors, and does not mention stepped lenses except in an unrelated sketch on the last page of the manuscript. The minutes of the meetings of the Commission go back only to 1824, when Fresnel himself took over as Secretary. Thus

7068-404: The same viewfinders as the preceding SLX; the standard viewfinder fitted has a folding waist-level finder with a built-in magnifier and a ground glass focusing screen with a central split-image rangefinder spot surrounded by a microprism collar, grid lines etched at regular intervals, and an integrated Fresnel lens . The viewfinder displays an image 55×55 mm (2.2×2.2 in), which is 93% of

7161-415: The shutter speed knob. The opposite side of the camera has a strap lug, hotshoe, and a slot to accommodate the rechargeable NiCd battery. Advertised stamina is approximately 500 to 600 exposures per charge. Two separate electronic shutter releases are provided on the bottom front corners of the camera, which may be operated by the photographer's right or left hand. Shutter speeds are selected by

7254-415: The size of telephoto lenses. Photographic lenses that include Fresnel elements can be much shorter than corresponding conventional lens design. Nikon calls the technology Phase Fresnel . The Polaroid SX-70 camera used a Fresnel reflector as part of its viewing system. View and large format cameras can utilize a Fresnel lens in conjunction with the ground glass , to increase the perceived brightness of

7347-418: The standard 6×6 back, a 645 back was available; both of these took film inserts. A bulk 70 mm perforated film back and a Polaroid (packfilm) back also were available. As shipped from the factory, the 6002 was fitted with a fixed film back which used the same interchangeable film inserts as the SLX. The 6008 continued using the same film magazine system as the 6006. The 6003 was fitted as standard with

7440-696: The test of the Cordouan lens in Paris, a committee of the Academy of Sciences reported on Fresnel's memoir and supplements on double refraction—which, although less well known to modern readers than his earlier work on diffraction, struck a more decisive blow for the wave theory of light. Between the test and the reassembly at Cordouan, Fresnel submitted his papers on photoelasticity (16 September 1822), elliptical and circular polarization and optical rotation (9 December), and partial reflection and total internal reflection (7 January 1823), essentially completing his reconstruction of physical optics on

7533-534: The third surface. The result was the lighthouse lens as we now know it. In 1826 he assembled a small model for use on the Canal Saint-Martin , but he did not live to see a full-sized version: he died on 14 July 1827, at the age of 39. The first stage of the development of lighthouse lenses after the death of Augustin Fresnel consisted in the implementation of his designs. This was driven in part by his younger brother Léonor—who, like Augustin,

7626-411: The traditional focusing knob on the left side of Rolleiflex SL66 and TLR cameras is not present. Film is loaded into interchangeable film holders, which are inserted into the hinged back at the rear of the camera. Both 6×6 and 645 rollfilm holders were available; the 645 back produces images that are 1 + 3 ⁄ 4 × 2 + 1 ⁄ 4  in (44×57 mm) in landscape orientation. In addition,

7719-660: The updated models, this is painted black. Like the Rolleiflex TLR, SL66, and the Hasselblad SLR, the SLX uses 120 or 220 rollfilm to produce frames of up to 6×6 cm (nominal); the actual image size is based on imperial units , measuring 2 + 1 ⁄ 4 × 2 + 1 ⁄ 4  in (57×57 mm). The camera has a modular design; the central camera body incorporates the single-lens reflex mirror and exposure controls, with interfaces accommodating interchangeable lenses, viewfinders, and focusing screens. Some of

7812-410: The whole forward hemisphere. The third version, which Stevenson confusingly called a "dioptric holophote", was more innovative: it retained the catadioptric Fresnel lens for the front hemisphere, but replaced the rear hemispherical reflector with a hemispherical array of annular prisms, each of which used two total internal reflections to turn light diverging from the center of the hemisphere back toward

7905-407: Was a rotating apparatus with eight "bull's-eye" panels, made in annular arcs by Saint-Gobain , giving eight rotating beams—to be seen by mariners as a periodic flash. Above and behind each main panel was a smaller, sloping bull's-eye panel of trapezoidal outline with trapezoidal elements. This refracted the light to a sloping plane mirror, which then reflected it horizontally, 7 degrees ahead of

7998-593: Was decided to build and outfit the Makapuu Point Light in Hawaii. Rather than order a new lens, the huge optic construction, 3.7 metres (12 ft) tall and with over a thousand prisms, was used there. There are two main types of Fresnel lens: imaging and non-imaging . Imaging Fresnel lenses use segments with curved cross-sections and produce sharp images, while non-imaging lenses have segments with flat cross-sections, and do not produce sharp images. As

8091-499: Was designed to marry features from modern small format SLRs, including motorized film transport and autoexposure, with the larger film size of medium format cameras. The first camera released was the 6006 (1984), which had features similar to the SLX, adding through-the-lens (TTL) off-the-film (OTF) flash metering and a fully-interchangeable film back. The film back introduced with the 6006 had an integrated, flexible dark slide ; it adds approximately 3 ⁄ 4  in (19 mm) to

8184-501: Was released in 1993, which added compatibility with PQS lenses; these feature an increased shutter speed of 1 ⁄ 1000  sec. Similar to the 6002, Rollei released the 6003 SRC1000 as a simplified companion to the 6008 in 1994. The 6003 removes the mechanical cable release socket and self timer; in addition, the default camera back takes interchangeable film inserts, but the standard back can be removed and used with 6008 film backs. The original 6008/6003 models were replaced with

8277-447: Was supplemented by reflecting ( catoptric ) rings above and below the refracting (dioptric) parts, the entire apparatus would look like a beehive. The second Fresnel lens to enter service was indeed a fixed lens, of third order, installed at Dunkirk by 1 February 1825. However, due to the difficulty of fabricating large toroidal prisms, this apparatus had a 16-sided polygonal plan. In 1825 Fresnel extended his fixed-lens design by adding

8370-515: Was supplied with a 2 m (6 ft 7 in) cable as standard, and a 10 m (33 ft) cable was available as an accessory. Rolleiflex 6000 System The Rolleiflex 6000 System is a line of medium format single lens reflex cameras made by Rollei , in regular production starting from 1983 with the 6006 . The 6006 was derived from the earlier SLX (1976) and retains compatibility with its lenses and accessories, adding an interchangeable film back with an integral dark slide . Like

8463-578: Was the first to replace a convex lens with a series of concentric annular prisms, ground as steps in a single piece of glass, to reduce weight and absorption. In 1790 (although secondary sources give the date as 1773 or 1788 ), the Marquis de Condorcet suggested that it would be easier to make the annular sections separately and assemble them on a frame; but even that was impractical at the time. These designs were intended not for lighthouses, but for burning glasses . David Brewster , however, proposed

8556-595: Was trained as a civil engineer but, unlike Augustin, had a strong aptitude for management. Léonor entered the service of the Lighthouse Commission in 1825, and went on to succeed Augustin as Secretary. The first fixed lens to be constructed with toroidal prisms was a first-order apparatus designed by the Scottish engineer Alan Stevenson under the guidance of Léonor Fresnel, and fabricated by Isaac Cookson & Co. using French glass; it entered service at

8649-511: Was witnessed by the Commission—and by Louis XVIII and his entourage—from 32 kilometres (20 mi) away. The apparatus was stored at Bordeaux for the winter, and then reassembled at Cordouan Lighthouse under Fresnel's supervision—in part by Fresnel's own hands. On 25 July 1823, the world's first lighthouse Fresnel lens was lit. As expected, the light was visible to the horizon, more than 32 kilometres (20 mi) out. The day before

#947052