- 12-24mm focal length.
- f/4 to f/22 aperture.
- Multi-layer coatings.
- Rotary type zooming system.
- Designed for digital cameras with APS-C sized CMOS and CCD sensors (DX).
Tokina Lens AT-X124ProDX Mark 2 (Canon)
Tokina Lens AT-X124ProDX Mark 2 (Canon)
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The AT-X 124 AF PRO DX lens is Tokina's first lens designed for
use exclusively on Canon and Nikon Digital SLR cameras having an
APS-C sized sensor.
This lens gives the Digital Photographer an ultra wide-angle zoom
lens that has the equivalent of an 18-36mm zoom range on a 35mm
film camera while maintaining a bright constant aperture of f/4.
Specifcations:
--------------
* Focal range: 12-24mm
* Maximum aperture: F/4
* Minimum aperture: F/22
* Optical construction: 13 elements in 11 groups
* Coatings; Multi layer
* Angle of view: 99 degrees - 61 degrees
* Minimum focus distance: 11.8 ins
* Magnification ratio: 1:8
* Zoom system: Rotary type zoom
* Aperture blades: 9
* Filter size: 77mm
* Dimensions: 84mm diameter
* Dimensions: 89.5mm length
* Weight: 540g
* Lens hood included: BH-777 Star bayonet
Features:
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Non-Rotating Filter Thread
--------------------------
Non-rotating 77mm filter threads mean special effect filters will
not change when the lens' focus is changed.
One Touch Focus Clutch
----------------------
Fast internal focusing with Tokina's One-Touch focus clutch
mechanism allows the lens to AF focus faster and sw
between auto and manual focus is as easy as snapping the focus
ring back and forth.
Automatic Correcting of Aspherical Abberation
---------------------------------------------
2 sharp-cut aspherical elements accurately correct aspherical
aberration usually associated with ultra-wide angle lenses.
Wide Aperture
-------------
Bright, constant f/4 aperture allows plenty of light to enter the
camera for shooting in a wide variety of photographic situations.
Materials Chosen for Ease of Use
--------------------------------
Chrome plated brass plate and all-metal zoom unit can stand
up to regular use while advanced polycarbonate outer lens barrels
reduce the weight of the lens.
Tokina Optical Technology
-------------------------
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-X124 AF PRO DX encompasses Tokina's new F&R
aspherical molded glass elements. 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 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.
Mechanical Technology
---------------------
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;
* Faster focusing
* Improved handling due to fewer movements near the center of
gravity
* More compact lens designs
* Superior use of filters because the barrel with the filter
thread does not rotate.
Focus Clutch Mechanism
----------------------
Tokina AT-X PRO series lenses all feature the patented "Focus
Clutch" Mechanism for sw 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
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.