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Siglas das Lentes

15 de junho de 2009

Você sabe o que a sigla que existe na sua lente quer dizer? neste tópico mais técnico quero compartilhar alguma das variações que existem. Entender o que uma lente VR faz, ou uma DX ou uma AF-S vai ajudar e muito na hora de escolher ou trocar a sua lente.

 

Lentes zoom
Possuem a habilidade de variar a distância focal e com isso mudar a ampliação da imagem simplesmente girando um anel no corpo da lente.
Por exemplo: uma lente 28-200mm torna possível fotografar em grande angular e em tele à partir do mesmo lugar.

Lentes de distancia focal fixa
As lentes de distância focal fixa oferecem um único ângulo de visão. Isso quer dizer que não é possível alterar o tamanho da imagem sem mudar a posição do local de onde se fotografa.
Entretanto as lentes de distância focal fixa oferecem aberturas maiores foco mais simples e são projetadas para um fim específico. Por isso produzem efeitos e resultados melhores para o fim aos quais foram projetadas.

Lentes macro

Usam ótica avançada para gravar imagens em tamanho real ou maiores. Estas características estão disponíveis em lentes com distancia focal fixa ou zoom.
Por exemplo: Uma lente macro com razão de 1:1 produz imagens em tamanho real no filme, 1:2 produz imagens com metade do tamanho real e 1:3 um terço do tamanho real.

ASP
Aspherical Lenses: Os elementos não esféricos de uma lente podem reduzir o numero total de elementos necessários em um tipo de lente. Eles podem melhorar o desempenho e ao mesmo tempo reduzir o peso e o tamanho da lente.
As lentes Aspherical maximizam a qualidade ótica e minimizam o tamanho e o peso das mesmas. As lentes Aspherical reduzem alguns problemas normalmente associados com grande angulares e zooms, tais como flare e distorções das bordas.

APO (apochromatic)
Estas lentes apresentam um projeto apocromático e vidros especiais de baixa disperssão (SLD – Special Low Dispersion) para uma aberração cromática mínima e alta qualidade em telefotografia oferecendo contraste e nitidez.
Lentes (APO) Apochromatic minimizam enormemente as aberrações cromáticas (fenomeno que ocorre quando a lente não é capaz de focar ondas de cores de diferentes comprimento no mesmo ponto. Isto provoca a formação de imagens em ponstos ligeiramente diferentes resultando em imagem de baixa qualidade).

RF IF (Internal and Rear Focusing)
O foco automático convencional é feito movimentando-se todo o conjunto de lentes ou apenas movendo o grupo de lentes frontal.
Para as lentes Tele e Macro a Sigma desenvolveu um sistema de foco interno que move um grupo de elementos dentro do tubo da lente, melhorando significativamente as capacidades macro. Para as super grande angulares com diametro frontal amplo criou o sistema de foco traseiro (Rear Focusing System) que move apenas o grupo de elementos traseiro.
Para as lentes de médio alcance usa o sistema de foco interno que move o grupo de elementos interno para permitir uma distancia focal mínima mais curta. Tudo mantendo um comprimento físico constante do corpo das lentes.

HSM (Hypersonic Motor)
Permite auto e manual foco de resposta rápica, virtualmente silencioso, como também sobreposição de foco somente manual

UC – Ultra Compact (Ultra compacta)
São as menores e mais leves lentes do seu genero disponíveis.

DG – Digital
As lentes com esta sigla são projetadas especialmente para câmeras digitais
SLR. Entretanto podem ser usadas normalmente em câmeras 35mm.

DL – Deluxe
As lentes DL são lentes completas a despeito de seu preço modesto. Como outras lentes Sigma elas são distribuidas com parassol original e incremento de 1/2 ponto em abertura manual scala de profundidade de campo e marca de correção de infravermelho.

DF – (Dual Focus)
As lentes Dual Focus (DF) são mais fáceis de segurar porque o anel de foco não gira durante o Auto Foco e mesmo assim proporciona rotação adequada do anel de focagem quando o sistema de foco estiver em modo manual.

HF – Helical focus
Este sistema elimimina a rotação da parte frontal da lente permitindo o uso de um parassol completo e facilitando o uso de filtros polarizadores.

EX – Excellence
Linha de lentes profissionais da Sigma. Estas lentes apresentam a sigla EX e o logo EX no corpo da lente.

DC
These are special lenses designed so that the image circle matches the smaller size of the image sensor of most digital SLR cameras. Their specialized design gives these lenses the ideal properties for digital cameras, the compact and lightweight construction is an added bonus ! including compact and lightweight construction.

APO MACRO Super
Tipo de lente Sigma Zoom Macro, desenvolvida para encurtar a distância focal minima e ao mesmo tento ter as caracteristicas de qualidade APO.

OS (Optical Stabilizer) Function
Estabilizador óptico nas lentes Sigma (IS nas canon)
Post Inicial: ftomas | CANON

EF (extended focus)
Canon electronic lens mount, used in all Canon camera since 1987. The previous mechanical lens mount carried the letters FD.

EF-S
The ‘S’ in the EF-S nomenclature stands for the term ‘short back focus’. This describes the system that allows the rear lens element of EF-S lenses to be positioned closer than normal to the image sensor of APS-C sensor cameras

DO
Stands for Diffractive Optic and is used on Canon lenses which utilize a unique diffraction grating to control chromatic aberration and reduce lens size and weight.

IS
Indicates that the lens utilizes Image Stabilization, which reduces vibration as much as 3 stops, allowing hand holding of long lenses at much lower shutter speeds than would otherwise be possible.

USM
stands for Ultrasonic Motor, a technology that uses sound waves to position the lens elements when focusing. This reduces size, weight and power consumption of the autofocus mechanism as well as increasing speed and allowing for manual override.

L
Canon’s designation for their top-of-the-line lenses is the letter L. These lenses are the best that the company knows how to make at any given focal length and aperture, and of course for a given price (which in the case of L series lenses is usually high).
Post Inicial: ftomas | TAMRON

IF
Internal Focusing, system that maintains the overall length of the lens during focusing

ASL
Aspherical

LD
Low Dispersion, Chromatic aberration is a form of optical noise that reduces the sharpness of an image. LD elements are made from special glass materials with extremely low dispersion indices that effectively compensate for chromatic aberration that is particularly a problem at the telephoto end

AD
Anomalous Dispersion, Anomalous Dispersion glass is a special optical glass that delivers an abnormally large partial dispersion ratio relative to a specific wavelength zone

XR
Extra Refractive Glass, Extra Refractive Index glass is said to bend light more effectively than normal or lower refractive index glass and can compensate for specific aberrations within an optical design.

DI
Digitally Integrated Design, is a designation Tamron puts on lenses featuring optical systems designed to meet the performance characteristics of digital SLR cameras

DI II
Lenses for Digital SLR Cameras Only – Lenses are designed for exclusive use on digital cameras with smaller-size imagers and inherit all of the benefits of our Di products. These lenses are not designed for 35mm film cameras and digital cameras with image sensors larger than 24mm x 16mm.

AF
These were the first generation of Nikon AF lenses. All Nikon autofocus SLR cameras are compatible with Nikon AF lenses which contain a CPU (central processing unit). These lenses are easy to recognise as the letters ‘AF’ can be is identified on the lens and they have CPU contacts on the rear of the lens as shown in the image below.
Early Nikon camera bodies which employ AF technology support basic autofocus but later cameras manufactured since 1996 with advanced metering systems require D (distance) information for exposure metering (see AF-D below). Cameras that support advanced 3D Matrix Metering require distance information to be transmitted from the lens, if a standard AF lens is used an abridged version of the metering system will be employed.

AF-D
Nikon introduced AF-D series lenses in 1996, while these lenses look similar to AF lenses they contained an encoding microchip that transmits focusing distance information to the camera body, this information is used to enhance the accuracy of the cameras exposure and flash metering systems. Cameras with advanced 3D matrix metering systems require AF-D compatible lenses to take full advantage of this technology. All current Nikon autofocus lenses transmit distance information to compatible cameras and are therefore AF-D compatible, AF-D lenses are recognised by the D designation marked on the lens as illustrated in the image below.

AF-G
AF-G lenses where introduced in 2000, these lenses are similar to AF-D lenses and offer the same functionality as AF-D lenses but do not feature an aperture ring. (an aperture ring is only required by older Nikon SLR cameras which can’t detect this information from the lens). For more information on AF-G lenses Click Here.

AF-S (AF-I)
Nikon AF-S lenses and it’s predecessor AF-I offer the same functionality as AF-D or AF-G lenses. The difference between these lenses is that AF-S / AF-I lenses contain a focusing motor built in to the lens, rather than using the auto focus motor built in to the camera body. This system enables faster focusing and in the case of the AF-S lenses near silent auto focusing.

DX
Nikon announced the introduction of DX lenses in 2002 incorporating technology from earlier lens types but offering better performance for Digital SLR users. DX lenses produce a small image circle which does not cover the 135 film area, therefore they are not recommended for use with film SLR cameras as cropping may occur. Their advanced design enables high quality optics and extended zoom ranges to be incorporated into compact lenses designs.

IF – Internal Focusing
Imagine being able to focus a lens without it changing in size, Nikon’s IF technology enables just that. Previously to 1977 when Nikon introduced IF lenses telephoto lenses required large amounts of turning the focus ring to move the front lens elements back and forth to allow focusing making the lens longer as you focused. With some large telelphoto lenses speacial screwing handles could be added to make focusing easier. Using IF designs all internal optical movement is limited to the interior of the none extending lens barrel.
This allows for a more compact lightweight construction as well as a closer focusing distance. In addition, a smaller and lighter focusing lens group is employed to ensure faster focusing. The IF system is featured in most Nikkor telephoto and selected Nikkor zoom lenses. Among these are the AF-S Nikkors which have virtually become standard equipment for fast-breaking sports photography around the world.

RF – Rear Focusing
Nikon’s rear focusing (RF) system, all the lens elements are divided into specific lens groups, with only the rear lens group moving for focusing.
Since rear lens groups are smaller than front lens groups, especially in high-speed telephoto lenses, RF technology makes it possible to drive the lens smoother and faster. RF also contributes to high optical performance.

VR – Vibration Reduction
This innovative system minimises image blur caused by camera shake, and offers the equivalent of shooting at a shutter speed three stops faster. It allows handheld shooting at dusk, at night and even in poorly lit interiors. The VR system also detects automatically when the photographer pans – no special mode is required.

ED – Extra-low Dispersion
Developed by Nikon optical designers and Nikon glass specialists, ED (Extra-low Dispersion) glass used in selected telephoto and telephoto zoom lenses provides superior superior sharpness and colour correction by effectively minimizes chromatic aberration to a degree that is remarkable in telephoto lenses

Aspherical Optics
A standard lens is made up of a combination of spherical lens elements. Individual “lenses” within the lens are commonly referred to as “elements”. A spherical element has an even curve to the surface of the glass. However, there can be problems with such elements; light entering the center of the lens and light entering at the edge may not be perfectly focused at the same point. This is called spherical aberration. More advanced computer assisted optical designs are creating lenses with more spherical elements. More spherical elements within a lens means a greater risk of spherical aberration having a negative impact on optical quality.
Wide-angle zoom lenses and wide-angle lenses with large apertures are especially at risk for spherical aberration.
To eliminate spherical aberration, Tokina employs aspherical all-glass elements in many of its optical designs to correct this problem. The aspherical shaped surface of the lens element focuses light rays entering both the center and edge of the element correctly at the film plane for an accurately focused image. In addition to correcting spherical aberration, these elements fully correct light quantity and distortion at the edge of the image and provide excellent results when used in combination with a floating element design.
Through a close collaboration with Hoya Corporation, the world’s largest optical glass manufacturer, Tokina has succeeded in producing high quality precision molded all glass elements with a greater aspherical shape than any other lens manufacturer. This technique is unparalleled in its technological sophistication and precision.

F&R Aspherical
This lens, the AT-X 235 AF PRO encompasses Tokina’s new F&R aspherical molded glass elements of an exceptionally large 50 mm diameter in the front and 20 mm diameter element at the rear. The 50 mm front element is one of the largest aspherical elements being employed in optical designs today. These give outstanding performance with very even illumination in the corners and correction of spherical aberration across the image area.

SD Super Low Dispersion
When standard optical glass is used in telephoto lenses, a phenomenon called chromatic aberration can occur. Chromatic aberration is the inherent tendency for glass to disperse (separate) a ray of light into the colors of the rainbow. The rainbow effect created by a glass prism is the most dramatic demonstration of chromatic aberration. In lenses, it is much less pronounced, but still creates slightly out of focus colors, akin to an “optical noise” that has a negative impact on the quality of the picture. To eliminate chromatic aberration, Tokina employs expensive, special glass material having super- low dispersion (SD) properties.
Lenses in the Tokina line-up with the SD mark incorporate these Super-Low Dispersion glass elements, minimizing the secondary spectrum or optical noise caused by chromatic aberration.

HLD
Tokina’s wide-angle and standard zoom lenses feature a higher quality of optical glass known as Tokina HLD (High-refraction, Low Dispersion) glass. Having higher refractive index and lower dispersion properties, HLD glass is far less likely than standard optical glass to create lateral chromatic aberration, which is often a problem with conventionally designed wide-angle lenses.

Multi-Coating
Reflections off the surface of lens elements are the enemy to any photographer and to every lens manufacturer. They are reduced or eliminated by bonding multiple layers of a transparent anti-reflection chemical to the surface of the glass. Tokina has developed and perfected a unique coating technique for all of its optics so that they will maintain faithful color reproduction and render clean, sharp images.

Floating Element System
When designing a lens, Tokina calibrated its astigmatism at all points between minimum focus distance and infinity so that it will give the best image results at all settings. However, when there are large differences between the focus limits, effect calibration is not possible. A floating element system incorporates optical elements that move in proportion to the focus setting of the lens. This allows astigmatism to be corrected. Many Tokina lenses employ floating element systems to provide optimum correction of astigmatism from minimum focus distance to infinity.

Internal Focus System
The two most used methods of focusing a lens are either the complete straight forward movement of lens elements (used mainly with single focal length lenses) or the rotation of the entire lens barrel group (used mainly with zoom lenses). The internal focusing system used by Tokina move each element group within the lens, but does not change the overall length of the lens. This is especially useful with telephoto designs.
The internal focusing system has a number of advantages including;
1. Faster focusing
2. Improved handling due to fewer movements near the center of gravity
3. More compact lens designs
4. Superior use of filters because the barrel with the filter thread does not rotate.

IFS (Internal Focus System)
By movement of the forward elements within the stationary main barrel: AT-X 235 AF PRO, AT-X 287 AF PRO SV, AT-X 280 AF PRO, AT-X 828 AF PRO

IRF (Internal Rear Focus System) Optical Pat.
By movement of rear elements only: AT-X 300 AF PRO

Focus Clutch Mechanism
Tokina AT-X PRO series lenses all feature the patented “Focus Clutch” Mechanism for switching the lens between auto focus and manual focus modes.
The manual focusing ring can move (be snapped) back and forth between an AF and MF position. When the focusing ring is forward in the AF position, it is not engaged to any of the internal focus gearing and will turn freely. Without the added weight of the metal ring the camera can auto focus the lens more quickly and smoothly.
For manual focus, simply rotate the focus ring all the way to one side or the other on the focus travel, either infinity or it’s closest focusing distance, then pull back (towards the mount plate) on the manual focus ring. While pulling back, rotate the ring from one side of the focus travel to the other. When the gears align, the focus ring will snap back into the MF position and the lens can be focused manually.
To return the manual focus ring to auto focus mode, simply snap the ring forward from any point.

One Touch Focus Clutch Mechanism
A refinement of the focus clutch mechanism has been incorporated in the AT-X 280 AF PRO Nikon and Canon mount, so that now the lens’ focus ring can be snapped back to the manual focus position at any time, from any position. This improvement means it is not necessary to change the AF/MF switch (on the body with Nikon or the lens with Canon) every time the lens is changed from auto focus to manual focus mode.
F – Objectivas originais bayonet F
AI – Auto Index
AIP – Com microchip
AIS – Ultimas de focagem manual
Series E – Serie mais Economica da Nikon, não se chamam Nikkor mas sim Nikon. Muitas das objectivas Auto-focus derivam desta serie, como a ainda produzida 50/1,8.
F3AF – Primeira tentativa AF da Nikon, nem vale a pena falar disso!
OP – Orthographic, objectiva sem perspectiva
Noct – A objectiva mais luminosa fabricada pela Nikon para 35mm, especialmente estudada para dar mais rendimento a 1,2, uma verdadeira lente nocturna!
PC – Perspective control, objectiva descentrável
DC – Diffusion/defocus control
GN – Regula o flash através do anel das aberturas

UV Nikkor – Transmite os comprimentos de onda dos raios ultra-violetas
Nas objectivas antigas, é ainda possivel encontral letras junto na descrição da objectiva. A nikon, indicava em latim, o número de lentes que compunham, por exemplo, a objectiva 28/2 N (nove elementos) ou 135/3,5 Q quatro elementos).

RS – Minolta
Stands for re-styled. Most lenses in Minola AF lineup are divided in two "categories"; original and RS (or new). Original lens versions are made mostly before 1990. At that time Minolta has started releasing restyled (RS) version of many original designs (like 50/1.7, 50/1.4). Mostly, new RS versions have introduced rubber focusing grip, circular blades etc. Original design isn’t changed.

G – Minolta; Sony
Stands for Gold and is supposed to describe lenses of the highest quality. It’s a marketing mark that Minolta introduced at the same time as RS lenses.
Minolta is describing G-series lenses as:
"G-series lenses are Minolta’s high-performance class optics. They have the best specifications, feature special advanced technology, and offer the best image quality of all Minolta lenses. G-series lenses are designed to meet the high expectations of the most demanding professional. The quality of the image they produce is among the finest in the industry.
Since G mark has started to be used after original version lenses have been produced no original lens model is labelled as G lens. However, there are original version lenses that with no doubt are deserving the same status as later G lenses (original 85/1.4, 200/2.8, 100/2 …)
Minolta has created a lot of confusion with naming and labelling their lenses. G-series lenses have never had G letter on the lens itself (there was rather a tinny "gold" ring on the lens). Sony, as a company of far superior marketing experiences has finally started labelling lenses properly and G mark is engraved on the lens.

D – Minolta; Sony, other lens manufacturer
D-Series lenses include distance-encoding device which enables improved calculation for flash exposure when used on cameras with ADI (Advanced Distance Integration) support. We know that even old lenses do provide subject distance info, but D lenses are very likely to do this more precisely.
As far we know ADI support is found on most modern AF lenses for Minolta a mount and you can recognize them by 8 lens contacts on the mount ( while older lenses have only 5 contacts). Whether or not ADI is bringing any significant improvement to flash exposure is debatable and users opinion are different.
A very common misunderstanding is that D mark means "Digital" which is absolutely wrong. D series lenses are in no way optimised better for digital cameras than non D lenses.

DT – Minolta; Sony
DT stands for "digital technology" and is supposed to describe lenses particularly optimized for digital cameras. In practice there is only one important thing about DT lenses you should be aware of; unlike non DT lenses these are covering image circle smaller than conventional 35mm lenses and are made with APS-C sized sensors. While you can mount these lenses on FF (film) cameras you will get severe vignetting due to reduced image circle. It is worth saying that DT lenses are in no aspects better than newer full frame lenses (like KM 17-35/2.8-4 of or 28-75/2. when image quality is concerned and it’s more a marketing buzz than anything else.

xi – Minolta
With the introduction of Minolta Dynax 7xi camera, Minolta has released new xi lenses. Xi lenses use electronic motors for both zooming and focusing and both are controlled by the camera.
While xi are working on our digital cameras image quality and overall usability was never embraced by most Minolta users which has made them more of an unsuccessful Minolta experiment than any improvement over original designs.

HS – Minolta
Stands for "high speed".
In 1998 Minolta introduced new HS versions of 200/2.8 (Minolta 200 F2.8 G APO HS), 300/2.8 (Minolta AF 300 F2.8 G APO HS) and 600/4 (MInolta AF 600 F4 APO G HS) lenses (followed by Minolta AF 80-200 F2.8 G APO HS (1993), Minolta AF 300 F4 G APO HS (1994) and Minolta AF 400 F4.5 G APO HS (1995) ) with a new high speed focusing gearing. This effort has resulted in faster AF performance compared to original design and while isn’t so silent as with SSM technology many do agree that HS lenses are (near) as fast as new SSM lenses.

SSM – Minolta; Sony
Stands for Supersonic-wave Motor.
At PMA 2003 Minolta has announced two new lenses; a new lenses AF 300 F2.8 APO G D SSM (has replaced Minolta AF 300 F2.8 G APO HS) and a completely new design AF 70-200 F2.8 APO G (D) SSM (replacement for the Minolta AF 80-200 F2.8 G APO HS ).
"SSM lenses uses the nature of piezo-electric element, which changes shape when voltage is applied. Compared to conventional DC motors, the supersonic-wave motor has characteristics that fit the lens drive, such as producing high torque from slow rotation and providing quick start and stop responses. By employing this motor, the SSM lenses provide ultra-quiet, ultra-smooth and superior AF operation".
SSM technology is providing fast, accurate and silent operation and it’s Minolta equivalent to Canon USM technology.
Sony did keep these lenses and introduced Sony variants; Sony AF 70-200 F2.8 G SSM and Sony AF 300 F2.8 G SSM

Fonte: Forum Fotrografia

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