1. EF-S18-55mm f/3.5-5.6 IS
Development objectives
The EF-S 18-55mm f/3.5-5.6 IS (Photo 1) is a standard zoom lens developed specifically for the EOS 40D and other APS-C sensor EOS Digital series cameras. The lens combines light weight, small size and superb cost performance with image stabilization. The primary aims of the lens's development are outlined below.
Feature 1 : Image stabilization in a lightweight, and compact body
Canon's engineers have been able to fit an image stabilizer unit in this lens while keeping it equivalent in size and weight to the non-IS EF-S 18-55mm f/3.5-5.6 II USM. A number of innovations made this possible including the compact zoom optics, the new smaller image stabilizer unit, the mechanical layout optimized to fit in very limited space, and the miniaturized electronic circuit board.
Feature 2 : Outstanding optical performance
The goal of the lens's optical design was to retain the acclaimed quality of the optics developed for the EF-S 18-55mm f/3.5-5.6 II USM while adding a new image stabilization mechanism. The inclusion of a precision aspherical element in the design provides excellent aberration correction, particularly of spherical aberrations, and ensures top image quality at all focal lengths (figures 2 and 3).
The focal length range is equivalent to 29-88mm in 35mm-film format.
Feature 3 : New smaller high-performance image stabilizer unit
A priority of this lens design was to keep its weight and size on par with that of the non-IS EF-S 18-55mm f/3.5-5.6 II USM. This meant that the image stabilizer unit had to fit in a very tight space.
We slashed the size and weight of the image stabilizer unit by redesigning the unit and reducing its component count. Some characteristics of the unit's new construction (Photo 2, Figure 4) are:
| • | A mechanism using ceramic bearing balls and the tension of three diagonally mounted springs holds the compensation optics lens barrel in place. The ceramic bearing balls' rolling action allows smooth movement of the compensation optics. |
| • | An actuator, consisting of permanent magnets and coils, drives the compensation optics lens barrel. |
| • | Dampers between the compensation optics lens barrel and its support frame cushion the impact of harmful vibrations from the springs' movement on the image-stabilization control. |
An optimized algorithm controls the drive of the new image stabilizer unit. With image stabilization on, the lens can deliver a stabilization gain of four f-stops in shutter speed.*
The lens is also able to automatically distinguish between panning and camera shake in normal shooting, and adjusts the IS mode accordingly. This feature permits for optimal image-stabilization in both situations and frees the user from concerns about mode selection.
* Generally, the effective limit for stable unaided handheld shooting is a shutter speed of about 1/[focal length x 1.6] seconds for APS-C sensor cameras.
Feature 4 : Optimal optics for digital SLRs
The lens configuration and coatings have been designed to minimize the flare and ghosting due to surface reflections from the imaging sensor that is found in digital SLRs. The configuration and coatings also provide excellent color balance.
Other features
• Fast autofocusing
A high-speed CPU and an optimized AF algorithm control the compact drive motor for fast autofocusing.
• Minimum focusing distance of 0.25m
The minimum focusing distance is 0.25m at all focal lengths, which is closer than that on the EF-S 18-55mm f/3.5-5.6 II USM. The maximum magnification is 0.34 (at 55mm).
• Circular aperture produces beautiful bokeh
The lens features an electro-magnetic diaphragm with a circular aperture that produces attractive bokeh (blurring effects).
• Redesigned switch shape prevents accidental mode changes
The focus mode switch has been reshaped to prevent the switch from being moved accidentally while shooting or transporting.
• Improved operability and high-grade exterior finish
This lens has been furnished with the same zoom-ring pattern and coating as our high-end models, giving a firmer grip and creating a high-grade exterior finish.
• Environmentally friendly design
The lens optics uses only environmentally friendly lead-free glass.
Furthermore, the lens design meets the environmental requirements of the European Union's RoHS Directive (Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment).
2. EF-S55-250mm f/4-5.6 IS
Development objectives
The EF-S 55-250mm f/4-5.6 IS (Photo 3) is an EF-S series telephoto zoom lens developed specifically for EOS Digital series cameras using the APS-C size sensor.
The design incorporates image stabilization. The image stabilizer unit features the same construction as the unit in the EF-S 18-55mm f/3.5-5.6 IS. It is light, very compact and gives superb cost performance. With just these two lenses, photographers have a focal length range of 29-400mm (35mm-film format equivalent), covering everything from wide angle to ultra telephoto.
The primary aims in the development of the EF-S 55-250mm f/4-5.6 IS are highlighted below.
Feature 1 : Image stabilization in a lightweight, compact lens
We took a number of steps - the compact zoom optics, the specially developed smaller image stabilizer unit, and the optimized mechanical layout - to include an image stabilizer in this lens while keeping it equivalent in size to the non-IS EF 55-200mm f/4.5-5.6 II USM.
Feature 2 : Outstanding optical performance
A new optical design was used to fit image stabilization within the lens' compact optics.
The design takes full advantage of the small image circle that is characteristic of EF-S lenses in order to cut weight and bulk from the optics and achieve a 4.5x zoom ratio while keeping the size nearly the same as the EF 55-200mm f/4.5-5.6 II USM.
Sharp image quality at all focal lengths is attained by using a UD lens element, which provides excellent aberration correction (figures 5 and 6). The focal length range is equivalent to 88-400mm in 35mm-film format.
Feature 3 : Newly developed high-performance image stabilizer unit
Equipped with a tiny image stabilizer unit (Photo 4) with the same construction as the unit on the EF-S 18-55mm f/3.5-5.6 IS, this lens boosts handheld camera steadiness by about four f-stops.* The lens is also able to automatically distinguish between panning and camera shake in normal shooting, and adjusts the IS mode accordingly. This feature permits for optimal image-stabilization in both situations and frees the user from concerns about mode selection.
* Generally, the effective limit for stable unaided handheld shooting is a shutter speed of about 1/[focal length x 1.6] seconds for APS-C sensor cameras.
Feature 4 : Optimal optics for digital SLRs
The lens configuration and coatings have been designed to minimize the flare and ghosting due to surface reflections from the imaging sensor that is found in digital SLRs. The configuration and coatings also provide excellent color balance.
Other features
• Fast autofocusing
A high-speed CPU and an optimized AF algorithm control the compact drive motor for fast autofocusing.
• Minimum focusing distance of 1.1 m
The minimum focusing distance is 1.1ｍ at all focal lengths. The maximum magnification is 0.31 (at 250mm).
• Circular aperture produces beautiful bokeh
The lens features an electro-magnetic diaphragm with a circular aperture that produces attractive bokeh (blurring effects).
• Redesigned switch shape prevents accidental mode changes
The focus mode switch has been reshaped to prevent the switch from being moved accidentally while shooting or transporting.
• Improved operability and high-grade exterior finish
This lens has been furnished with the same zoom-ring pattern and coating as our high-end models, giving a firmer grip and creating a high-grade exterior finish.
• Environmentally friendly design
The lens optics use only environmentally friendly lead-free glass.
Furthermore, the lens design meets the environmental requirements of the European Union's RoHS Directive.
This month we brought you information on two new EF-S lenses.
Tables 1 and 2 provide the main specifications and the extension tube data for the two lenses.
| EF-S18-55mm f/3.5-5.6 IS | EF-S55-250mm f/4-5.6 IS | ||
| Focal length/aperture ratio | 18-55 mm f/3.5-5.6 | 55-250mm f/4-5.6 | |
| Lens construction | 11 elements in 9 groups | 12 elements in 10 groups | |
| Angle of view | Diagonal | 74°20' - 27°50' | 27°50' - 6°15' |
| Vertical | 45°30' - 15°40' | 15°40' - 3°30' | |
| Horizontal | 64°30' - 23°20' | 23°20' - 5°20' | |
| Minimum focusing distance | 0.25 m | 1.1 m | |
| Maximum magnification/field of view | 0.34x (at 55mm) | 0.31x (at 250mm) | |
| Aperture blades | 6 (circular) | 7 (circular) | |
| Minimum aperture | F22 - F38 | F22 - F32 | |
| Filter size | 58 mm | 58 mm | |
| Maximum diameter x length | 68.5 x 70 mm | 70 x 108 mm | |
| Weight | 200 g | 390 g | |
| Hood | EW-60C (sold separately) | ET-60 (sold separately) | |
| Case | LP814 (sold separately) | LP1016 (sold separately) | |
| Price | ¥33,000 (taxes separate) | ¥45,000 (taxes separate) | |
EF-S 18-55mm f/3.5-5.6 IS
| Setting | Focusing distance (mm) | Working distance (mm) | Magnification (x) | ||||
| Near | Far | Near | Far | Near | Far | ||
| EF12 II | 18mm | Incompatible | |||||
| 55mm | 205 | 378 | 34 | 212 | 0.64 | 0.23 | |
| EF25 II | 18mm | Incompatible | |||||
| 55mm | 196 | 266 | 26 | 100 | 1.00 | 0.51 | |
| Setting | Focusing distance (mm) | Working distance (mm) | Magnification (x) | ||||
| Near | Far | Near | Far | Near | Far | ||
| EF12 II | 55mm | 351 | 411 | 183 | 259 | 0.28 | 0.22 |
| 250mm | 1075 | 5274 | 865 | 5081 | 0.60 | 0.05 | |
| EF25 II | 55mm | 281 | 297 | 113 | 145 | 0.47 | 0.48 |
| 250mm | 918 | 2692 | 708 | 2499 | 0.46 | 0.11 | |