Friday, August 11, 2006

How to select objective?

Objectives Canon

With the development of their system Canon EOS engineers Canon placed motors for the focusing and controls of diaphragm directly in the objective. Therefore in bayonet Canon EF there is no mechanical joining whatever, all information is transferred at a high speed by electronic method. Each focusing motor is developed in accordance with the characteristics of objective, which ensures optimum operating characteristics and speed.

At the present moment in the majority of objectives EF of middle class is used annular ultrasonic motor (ring-USM). It is direct-drive motor without the mechanisms of transfer; therefore its work is characterized by rapidity and reliability. The advantages of ultrasonic motors are not limited to an improvement in the performance characteristics of self-focusing. The majorities of objectives of the type EF USM are equipped with the function of the constant manual focusing FTM (full- Tim manual), with the aid of which at any moment of time it is possible to correct the focusing, determined automatically, which makes it possible to obtain excellent effectiveness in the work. Only low-order objectives Canon EF (such as Ef28-90 mm f/4-5,6 USM) is used the simplified version USM- motor - micro-USM. Such objectives do not permit implementation of manual self-focusing, without being switched into the manual regime of focusing, or they possess the lower speed of focusing. Only objective with the focusing motor micro-USM, which possesses possibility FTM - this EF 50/1.4.

Among objectives Canon EF it is worthwhile to isolate the professional high-quality objectives of series L, which use the most contemporary technologies and possessing the highest technical characteristics.

Objectives Ts- e of 24 mm f/3.shchL, Ts- e of 45 mm f/2,8 and Ts- e of 90 mm f/2,8 have manual focusing. Reduction "TS" in the names of these objectives designates "tilt-shift" (inclination- shift) and reveals the method of using the data of objectives. Objective Canon EF 135 mm f/2.8 soft-focus makes it possible by optical means to give softness to image. This property makes it possible to obtain very beautiful effects, for example, during the photographing of portraits.

Extension rings (Extension Tube EF12 and EF25) and adapter lenses (Close-Up Lens 250D, 500D, 500) will be necessary by you, if you want to remove from the distance of altogether only of several centimeters from the object and to obtain photographs with the high level of an increase. Specially for the surveys on a scale 1:1 with use EF 50 mm f/2,5 Compact Macro it is proposed Life-Size Converter EF. An even large selection of equipment becomes accessible with the use of adapters for macro objectives FD-EOS - Lens Mount Converter FD-EOS and Macro Lens Mount Converter FD-EOS.

By index "IS" (Image Stabilization, the stabilization of image) are designated the objectives, equipped with the stabilizer of image. The optical stabilizer of image makes it possible to use longer endurances during the photographing from the hands, without fearing to obtain "blurry". The stabilizer of image uses two gyro-sensors; signals from gyro-sensor are transferred to the compensating optical system, which neutralizes vibration.

One cannot fail to note the special protected version of bayonet O- ring. Canon EOS 1V with one of the new IS-superteleob7ektivov are connected practically air tightly because of it. This substantially improves the protection of camera and objective. For example, now they can completely safely be located even in the rain

Objectives Minolta

Quite high-aperture, best according to quality images and mechanical strengths objectives Minolta, intended for the use for professional purposes, are designated by index "G".

Objectives Minolta, which have in their name index (D), are equipped with the built-in decoder of the distance of sharp focusing, necessary for the valuable work on apparatuses Minolta Dynax 7, Minolta Dynax 5 and Minolta Dynax 4 systems ADI (Advanced Distance Integration) - control systems of the flash, which makes it possible to gain a maximally precise dosing of the light of flash under the most different conditions. Some of the objectives of series D (for example AF 24-105/3.5-4.5(D), AF 100-300/4.5-5.6(D) Apo, AF 100/2.8(D) macro and AF 85/1.4G(D)) - are equipped with the built-in mechanical switch, unlocking the drive of self-focusing with the focusing ring with the switched one auto-focus. This solution made it possible to make a ring of manual focusing sufficiently to wide and convenient, after avoiding inconveniences from the revolving ring of focusing with the use of auto-focus.

Abbreviation SSM in the name of recently announced professional objectives Minolta AF 28-70/2.8 G (D) SSM, Minolta AF 70-200/2.8 G (D) SSM and Minolta AF 300/2.8 G (D) SSM designates the presence in their construction of the built-in direct-drive ultrasonic motor of the type SSM (structurally close to the drives type USM, HSM and SWM from Canon, Sigma and Nikon respectively). This type of drive makes it possible to considerably improve dynamics and to increase the rate of conducting the process of self-focusing.

In long-distance objectives Minolta, which have in their name index "APO", special attention given the minimization of the chromatic aberrations, which worsen the clearness of the reproduction of small image details. Objective Minolta STF 135mm f/2.8 [T/4.5 ] - only in system Minolta Dynax objective with the manual focusing. This objective gives to photographer the unique possibility to govern smearing background independent of the diaphragm, with which the survey (first of all this possibility it is claimed in the portrait survey) is produced.

Objective AF 100mm f/2.8 SOFT FOCUS, also oriented in essence to the portrait survey, is capable to create image from the clear and the contrasting to the soft and the air. The adjustment of the degree of the "softening" of image is produced by the turning of ring on the objective, with

This degree of effect easily is checked on the image in the viewfinder. Zoom lenses Minolta of a series "- the xi", differ in terms of the ability to change focal length in the signals from the camera. The production of these objectives is at present ended, since none of the now produced cameras Minolta uses entirely the possibility of zooming motor.

Objectives Nikon

With marking of objectives Nikon adapt the following designations: D - the auto-focal objectives of series D transfer information about the distance of focusing into the camera. Therefore with the calculation of exposure the object distance of survey is considered that it helps to more accurately select the exposure parameters with the work with the flash.

G - in contrast to objectives D- type, objectives Nikkor of series G do not have ring of control of diaphragm, and, correspondingly, mechanically is not transferred the value of diaphragm to the camera. Therefore the objectives of series G cannot be exploited with the apparatuses with the manual focusing, but with the auto-focal apparatuses for earlier releases (F501, F601, F801/801s, F70, F90/90x) the objectives of series G they can be used only in the program regimes and the regime of the priority of endurance. The distance of focusing is transferred.

AF-S - in objectives Nikkor of the type AF-S is used the ultrasonic motor (Silent Wave Motor), with the aid of which is accomplished the self-focusing. Each motor is developed under the concrete objective, which makes it possible to in the best way ensure rapid and precise self-focusing.

M/A - in this regime objectives AF-S with can be practically instantly switched from the regime of self-focusing into the regime of manual focusing.

VR - the system of the suppression of vibration - one of the last novelties in objectives Nikkor, with its aid you will be able to remove from the hands without "blurry" the subjects, in which earlier could not be manage without the support.

DC (Defocus-image Control) - in these objectives is used the unique system for control of defocusing image. It makes possible for photographers to check the degree of spherical aberration in the front or rear track layout of rotating the established on the objective ring DC. in this case it is formed the round ring of defocusing, ideal for the portrait survey.

IF - system of internal focusing, because of it focusing is achieved due to the displacement of the internal groups of lenses. This makes it possible to decrease the overall sizes and the weight of objective, and to also produce survey on the shorter distances of focusing. The speed of self-focusing also grows.

RF - "rear" focusing. With use RF the focusing is achieved due to the displacement of rear, lightest, the groups of lenses. This also accelerates self-focusing.

CRC (Close- rank Correction) - correction for the survey at the close distance. This system assumes displacement with the focusing not only of the focusing lens component, but also independent from it displacement of the corrective component (usually locating v in the rear group of lenses). System CRC makes it possible to attain maximum image quality not only during the focusing to infinity, but also with the focusing to the closely spaced objects.

ED (Extra-Low Dispersion) - for decreasing the chromatic aberration in objectives Nikkor is used the specially developed glass- with the ultralow dispersion.

SIC (Super Integrated Coating) - the firm "super-integrated" multilayer coating of lenses decreases the effects of reflection and fulguration.

ASP - for eliminating the aberration are used aspherical elements.

Objectives Pentax

All objectives Pentax have the firm multilayer enlightenment SMC. the auto-focal objectives Pentax FA (in contrast to the earlier objectives Pentax F) they transfer into the apparatus the value of the diaphragm (for zoom obectives - with each focal length), with which frequency contrast characteristic (MTF) of objective will have maximum value. This information some apparatuses Pentax are used, selecting optimum diaphragm with the work in the program regimes.

Objectives Pentax FA power zoom have a control capability of the zooming process both of the apparatus and by hand - by the built-in motor or by the turning of the zooming ring by hand. Entirely the possibility of objectives Pentax FA power zoom it can use only removed recently from production apparatus Pentax Z -1P.

In the objectives, whose name includes index LD, are used lenses from the glass with the ultralow dispersion.

The application of aspherical lenses, which make it possible to improve the quality of the image of objective with a smaller number of lenses, is mapped into the name of objectives Pentax by marking AL. Index [ IF ] attests to the fact that the focusing of objective is produced by the displacement of the internal components of objective, but not by front component. Internal focusing makes it possible to accelerate the process of guidance to the sharpness (due to the smaller mass and the moment of the inertia of moving elements), and also - to make a front objective lens of fixed, giving the possibility of applying the light polarizing filters and effective "Cruciferae" of blends. Quite high-aperture, best according to quality images and mechanical strengths objectives Pentax, intended for the high(ly)-class professionals, have in their name a symbol "*".

The objectives of series Pentax FA Limited are characterized by uncommonly compact sizes and very rugged construction with the high quality of image.

Objectives Sigma

Company Sigma lets out now the rule of the specular cameras Sigma SA, change optics and flashes to them. However, it is most widely known as the most fruitful and most active of the "independent" producers of change optics to reflex camera of other stamps. The rule of objectives Sigma consists in essence of the zoom lenses of different class, high-aperture wide-angle, long-focus and macro- objectives. In the construction of optics Sigma find use all quite advanced technologies - for example aspherical optical elements and lens from the glass with the ultralow dispersion. Also, in the number of the first, company Sigma developed and injected direct-drive ultrasonic engine in the drive of self-focusing (HSM - HyperSonic Motor - analog USM (Canon) and SWM (Nikon)). On the exhibition Photokina-2002 passed recently by company Sigma is presented the objective with the optical stabilization (SIGMA AF80-400mm f/4.5-5.6 EX OS), which acts similarly to similar systems of IS (Canon) and VR (Nikon). The distinctive special feature of all objectives Sigma are the convenient rubber-lined ring of manual focusing, the scale of distances with the hyperfocal marks, metallic bayonet. Bulk of objectives Sigma they are completed by the special blend (perfect hood), and some - even and by convenient case for the transport and the storage.

In the names of objectives Sigma adapt the following indices:
Aspherical - indicates the application in the construction of the objective of one or several optical elements with the aspherical surfaces. Aspheric makes it possible to decrease the number of lenses in the construction of objective, and consequently - to decrease the mass and the dimensions of objective. Also the application of aspherical lenses can improve the definition characteristics of optics.

EX - Excellence. The objectives of series EX are characterized by professional characteristics - high candlepower, convenient control, intensified by construction, high quality of image. Is separated them from the remaining mass of optics Sigma and unique design.

APO - apochromatic design. In the objective- apochromats special attention is given to the elimination of the chromatic aberration, which leads to worsening in the sharpness and appearance of colored edging of small image details. Apochromatic correction is achieved due to the application in the construction of the objective of lenses from the glass with the ultralow dispersion (SLD - Super-Low Dispersion glass), and also the specially calculated optical diagram.

IF (or RF) - the focusing of this objective is produced with the aid of the displacement of small over the mass and the dimensions of internal (or rear) lens component. This diagram of focusing gives the possibility not only to accelerate focusing and to unload the engine of the drive of auto-focus, but also it makes it possible with the large convenience to use effective petalous blend, polarization and shading filters.

HSM - indicates the built-in the objective ultrasonic focusing motor (Hyper-Sonic Motor). This motor in the comparison with the traditional has the high speed of focusing, best dynamics, minimum noise with the work. The versions of objectives Sigma with HSM- motor are produced for the installation to apparatuses Sigma, Canon and Nikon.

UC - separately compact objective (Ultra Compact), which has minimal sizes and weight.

DL - Deluxe. The inexpensive objectives of this series are equipped at the level of more dear fellows, for example they have the valuable scale of distances with the markers of depth of focus and the indicator of focusing for the IR beams, metallic bayonet, special blend.

DF - Dual Focus (the double focusing). The objectives of series DF are conveniently use both in the regime of self-focusing and in the regime of manual focusing. "craftiness" consists in the special construction of the ring of manual focusing. In the regime AF it remains of fixed, while in the regime manual focusing ring automatically will be unblocked and has characteristic "oily" motion with a certain effort (as in objectives with the manual focusing).

HF - Helical Focus. In the objectives with the helicoid focusing the front focusing lens component with the focusing does not revolve, what gives the possibility to use the shaded and light polarizing filters, and also - effective "petalous" blend.

DEG - Digital Grade - a series of the wide-angle lenses, which are intended for the use both on the tape and on the digital cameras.

Macro - this objective can be used for the survey on a large scale (to 1:4 or to 1:2). Specialized macroobiectives Sigma (50/2.8 and 105/2.8) make it possible to gain scale 1:1.

OS - Optical Stabilisation - objective with the device of the optical stabilization of image.

Objectives Tamron

The Japanese company of Tamron obtained reputation not only as one of the "independent" producers of optics for the reflex cameras of other firms, but also as the producer of objectives for the sredneformatnykh specular and ranging apparatuses Zenza Bronica. Among the production of company Tamron are very interesting the objectives of professional class with the best optical and mechanical characteristics (series of optics SP - super performance). This series of optics absorbed into itself all best contemporary optical technologies and 50 years experience of the opticians of the company Of tamron. However, in the assortment of firm Tamron there is one additional separately interesting part - this of "superzoom" (compact objectives with the very broad zooming band). In the development of this category of production the company succeeded so, that superzoom from Tamron are already traditionally considered best in their class. As one additional proof that serves the close collaboration of companies Pentax and Tamron with creation and production of some amateurish objectives Pentax.

In the names of objectives Tamron adapt the following indices:

SP - Super Perfomance. Professional series of the objectives, which are characterized by maximum image quality, by high candlepower and by extra-heavy construction.

Xr- Extra Refractive Index. In the construction of objective are used the lenses from the glass of special it is quality, that are characterized by the superhigh refractive index of light. Such lenses are more compact and light, which makes it possible to decrease weight and overall sizes of entire objective.

LD - Low Dispersion Glass - indicates the application in the objective of lenses from the glass with the ultralow dispersion, which makes it possible to make a reproduction of outlines and fine details along entire image field clearer.

IF - Internal Focusing the focusing of this objective is produced with the aid of the displacement of small over the mass and the dimensions of internal (or rear) lens component.

Aspherical - indicates the application in the construction of the objective of one or several optical elements with the aspherical surfaces. Aspheric makes it possible to decrease the number of lenses in the construction of objective (and consequently - to decrease the mass and the dimensions of objective) with best image quality.

Objectives Tokina

Objectives Tokina it develops and is produced the Japanese concern THK (Tokina-Hoya-Kenko), known also on light filters Hoya and Kenko, lengthen rings and teles-converter Kenko. Optics Tokina of all series is characterized by extra-heavy construction because of the wide application of light metallic alloys for preparing the hull details of objectives. The special interest cause objectives Tokina of the professional series AT- X AF Pro and AT- X AF. In the objectives of these series widely adapt the most contemporary achievements of rasschetnoy optics - aspherical surfaces of lenses, lens from the glass with the ultralow dispersion, the "floating" with the focusing optical elements, internal and the "internal rear" focusing of objectives. Also is very remarkable the design of optics of series AT- X pro. Deep incision on the rubber revetment of the zooming rings and manual focusing, ergonomic "rough" surface of the housings of objectives, disconnected ring of manual focusing "Focus Clutch Mechanism" and other design and ergonomic special features of objectives Tokina AT- X pro add pleasures with the work by them. The basic carrying structural parts of objectives Tokina of series AT- X are made from duralumin with the special coating, the contiguous details are covered with special lubricant. Therefore the ease of the motion of all moving parts with the minimum gaps remains over a wide range of temperatures, and the construction of objectives Tokina of series AT- X easily maintains long-term usage with the professional loads.

In the construction, the names and the descriptions of objectives Tokina are encountered the following designations: AT- X ("Advanced Technology-Extra.") - the concept of uncompromising counting and production of optics, using all most contemporary and perfect methods and materials. The objectives of series AT- X have high optical characteristics, durable, long-lived construction, and they are designed for the lasting operation under the quite severe conditions.

Focus Clutch Mechanism - the system of manual focusing, which made it possible to use with the manual focusing wide and convenient ring with the smooth "oily" motion. With the self-focusing this ring remains fixed, it does not interfere with conveniently being held for the objective and does not overload the engine of self-focusing. For the switching from the regime of automatic focusing into the regime of manual focusing it suffices to only move the ring of focusing to itself (in the direction of vehicle). The special construction of this mechanism completely excludes the possibility of random switching. In the construction of some objectives of the last issue (for example At- X 280af PRO 28-.80mm f/2.8), designed for the operation with cameras Canon EOS and Nikon AF, is used the extended modification of this mechanism, which was called name "One-Touch Focus Clutch Mechanism", which made it possible to pass from the regime of manual focusing into the auto-focal regime by one motion of the ring of focusing, without the need for on/off the regime of self-focusing by separate switch on the apparatus or the objective.

IF (Internal Focus System) - the system of internal focusing, i.e., the focusing of objective by the motion of small throughout the mass and according to the sizes to the internal group of lenses. Therefore the process of self-focusing is conducted more rapid and it is more dynamic, with smaller noise and load on the AF- engine, is excluded the unbalance of objective in the process of focusing. Furthermore, internal focusing makes it possible to prepare more compact objectives, and also - with the large convenience to use the polarization and shading light filters, to use the effective "Cruciferae" by blends. IRF (Internal Rear Focus System) - the version of the system of the internal focusing, when focusing is achieved by displacement in the last group of lenses.

AS (Aspherical Lens - aspherical objective) - in the construction of objective are used optical elements with the aspherical surfaces. Aspheric makes it possible to decrease the number of lenses in the construction of objective, and consequently - to decrease the mass and the dimensions of objective. Also the application of aspherical lenses improves the definition characteristics of optics.

SD (Super-Low Dispersion Glass) - indicates the application in the objective of lenses from the glass with the ultralow dispersion. Such types of glass make it possible to considerably decrease the chromatic aberration, and it means - to make clear a reproduction of outlines and fine details not only on to center sequence, but also along entire image field.

Floating Element System (system with the floating elements) it makes it possible to avoid worsening in the sharpness with the focusing to the close distances. For this in the objective is provided one additional mobile ("floating") group of lenses, whose displacement with the focusing makes it possible to compensate aberration and to improve definition characteristic of objective during the photographing on any scale.




Post a Comment

<< Home