聚焦系统
| 焦距 |
12 - 28 mm |
| 对角线视角（最大） |
99.37 ° |
| 对角线视角（最小） |
54.73 ° |
| 最近聚焦距离 |
0.25 m |
| 光阑叶片数量 |
9 |
| 固定焦距 |
56 mm |
| 最大光圈 |
22 |
| 最小光圈 |
4 |
AT-X 12-28 Pro DX, F4/22, 14 Elements / 12 Groups
<b>Wide Zoom Range</b>
The new Tokina AT-X 12-28mmF/4lens has a super-wide to standard zoom range while maintaining a constant fast f/4.0 aperture. This makes ita very versatile lens for different photo applications such as scenery, street scenes photography and event coverage. The lens is designed for DSLR cameras with APS-C (DX) sized sensors.
<b>New Optical Design</b>
A new optical design using aspherical elements and super-low dispersion glass matches even the highest mega-pixel DX sensors cameras available today.
One asphericallenselement is positioned in the front group. This together with another precision molded glass aspherical lens element placed in the rear group ideally focuses marginal light rays andmaintains sharpness at the edgeswhile also correcting distortion. The use of two different SD(Super-low Dispersion)glass elements,typeFK01 and FK03,correctschromatic aberration. The combination of all these specialized elements in the optical design yield excellent sharpness and color.
<b>New auto focus mechanism</b>
The new AF “GMR magnetic precision” control sensor is capable offastauto-focus. Tokina placed the new sensor closerto the drive unit in the lens for faster communicationbetween the controller and AF motor. This combined with the motor's high-precision focus control yields faster, more accurate auto-focus.
Additionally, a brand new “SD-M” (Silent Drive-Module) has greatly lowered the sounds emitted by the auto focusdrive system allowing for much quieter AF. Both Canon and Nikon mounts have a built-in AF motor to make them auto-focus compatible with all current camera bodies.
<b>Compact body design</b>
The Tokin AT-X 12-28mmF/4 compact designmakes the lens easy to carry and handle. Manual focus is achieved through Tokina's one-touch focus clutch AF/MF mechanism. Simply slide the manual focus ring forward for auto-focus or back for manual focus operation. The lens focus ringis damped in the manual mode for smooth and precise focusing.
In addition thelens has a 77mm filter size allowing filters such as the Hoya HD low-profilecircular polarizer or UV to be used.
