This month's Technical Report introduces two EF lenses announced together with the EOS-1D Mark II in January 2004: the EF28-300mm f/3.5-5.6L IS USM, a high-magnification (approximately 11x) L-series zoom lens, and the EF70-300mm f/4.5-5.6 DO IS USM, a compact telephoto zoom lens using Canon's proprietary three-layer DO Lens.
The EF28-300mm f/3.5-5.6L IS USM is an L-series ultrahigh-magnification zoom lens developed as the successor to the EF35-350mm f/3.5-5.6L USM 10x zoom lens released in 1993. The new lens offers higher performance, extended wide-angle coverage, and higher magnification.
The concept of development is as follows:
| • | Ultrahigh-magnification (about 11x) zoom covering the entire range from wide-angle to telephoto |
| • | Image stabilizer (IS) incorporated |
| • | New optical system for high quality images befitting L-series lenses |
| • | Ideal for digital SLR cameras also |
| • | Dust-and moisture-proof construction |
Feature 1: Ultrahigh-magnification zoom range from 28mm wide-angle to 300mm telephoto
The EF28-300mm f/3.5-5.6L IS USM has a six-group optical system with six moving groups and the inner focusing system by the second group. It incorporates new design features that give ultrahigh-magnification zoom ranging from 28mm wide-angle to 300mm telephoto (about 11x).
Feature 2: The combination of UD and aspherical lens elements provides high image quality characteristic of L-series lenses
The optical system, with 23 elements in 16 groups (see Fig. 1), uses two precision molded glass (GMo) aspherical elements and one replica aspherical element, resulting in excellent correction for aberrations that occur during zooming.
In addition, the three UD lenses minimize longitudinal and lateral chromatic aberrations. The result is high quality images with excellent resolution and high contrast throughout the entire zoom and focusing range (see Fig. 2).
Fig. 1 EF28-300mm f/3.5-5.6L IS USM Optical System at Wide Angle (28mm)
Feature 3: Image stabilization of about three shutter speeds
The EF28-300mm f/3.5-5.6L IS USM uses the same shift-lens image stabilizer system as other Canon IS-series lenses. The supplementary optical system instantly moves perpendicular to the optical axis to cancel out the camera shake. Through the highly sensitive IS drive control and the improved control algorithm, the EF28-300mm f/3.5-5.6L IS USM gives image stabilization equivalent to using a shutter speed three steps faster.
The image stabilizer is activated within 0.5 seconds after pressing the shutter button halfway, allowing the user to capture the decisive moment.
The EF28-300mm f/3.5-5.6L IS USM has two image stabilizer modes. Mode 1 is effective for stationary subjects and mode 2 is best for panning with a moving subject.
Feature 4: Lens coating optimized for use with digital SLR cameras
The EF28-300mm f/3.5-5.6L IS USM features lens coating optimized for use with digital SLR as well as film SLR cameras. As a result, it successfully realizes both appropriate color balance and minimization of ghost and flare attributable to surface reflections from the digital imaging element.
Feature 5: Excellent dust-and moisture-proof construction
Dust and moisture resistant construction (see Fig. 3) is adopted in the mount area, switch panel, zoom ring and focusing ring, preventing moisture and dust from reaching the interior of the lens, enabling its use under harsh conditions.
• Minimum focusing distance of 0.7 meters
The minimum focusing distance of 0.7m through the entire zoom range was achieved by increasing the power of the focusing lens group. It also gives a maximum magnification of 0.3x at 300mm telephoto (81 x 121mm field of view).
• Silent, high-speed AF
The ring-type ultrasonic motor (USM) and inner focusing system contribute to silent, high-speed autofocus (AF).
• Manual focusing enabled even in AF mode
The EF28-300mm f/3.5-5.6L IS USM has full-time manual focusing that allows user to manually focus after one-shot AF operation without leaving AF mode.
• Zoom touch adjustment ring
As with the EF35-350mm f/3.5-5.6L USM, the EF28-300mm f/3.5-5.6L IS USM features a zoom touch adjustment ring to adjust the ease of zoom movement or to lock the zoom at any focal length.
• Circular aperture for attractive boke effects
The lens aperture remains virtually circular from wide open to about two stops down, providing attractive blur effects (boke).
• Environmentally friendly lead-free glasses
The optical system contains only environmentally-friendly lead-free glasses.
• Easy-to-use detachable tripod mount
The Tripod Mount C (W) opens so it can be attached or detached while the lens is mounted on the camera. It is a standard accessory.
The EF70-300mm f/4.5-5.6 DO IS USM is a compact telephoto zoom lens that was developed to extend the range of DO lenses (multi-layer diffractive optical element) which debuted with the introduction of the EF400mm f/4 DO IS USM in 2002.
The concept of development is as follows:
| • | DO lens optimized for zoom lens optics |
| • | Far more compact optical system, but higher image quality with newly developed three-layer DO lens |
| • | Image stabilizer (IS) incorporated |
| • | Ideal for digital SLR cameras also |
Feature 1: Newly developed three-layer DO lens optimized for zoom lens
The DO lens is an innovative optical element using the principle of light diffraction. Canon's EF400mm f/4 DO IS USM, released in 2002, was the world's first camera lens to use a DO lens, realizing both significant miniaturization of optical system and high image quality.
With zoom lens, however, the angle of view varies with the focal length, inevitably resulting in significant changes in the angle of incident light entering the DO lens. With a zoom lens the use of the original two-layer DO lens would cause unwanted flare-causing diffracted light, significantly lowering the image quality.
Consequently, Canon developed a new three-layer DO lens (see Fig. 4) suitable for zoom lenses, with a construction of three laminated diffraction gratings.
| * | For detailed information on the basic principles of the diffraction phenomena and DO lens, please refer to the Technical Report June 2001 issue. |
The three-layer DO lens is effective in correcting the increase in chromatic aberration that accompanies increased compactness of an optical system. This resulted in the EF70-300mm f/4.5-5.6 DO IS USM being approximately 28% shorter overall length than the conventionally designed EF75-300mm f/4-5.6 IS USM telephoto lens, with a similar focal length and maximum aperture (see Figs. 6 and 7).
Fig. 6 EF70-300mm f/4.5-5.6 DO IS USM Optical System at Wide Angle (70mm)
Furthermore, the aspherical effect of DO lens and the use of high-precision GMo aspherical lens provide excellent correction of spherical aberration and give outstanding image quality with high resolution and contrast comparable to an L-series lens (see Fig. 8).
Fig. 8 MTF Characteristic Charts of EF70-300mm f/4.5-5.6 DO IS USM
Canon's new compact image stabilizer unit and improved control algorithm achieve an image stabilization effect equivalent to a shutter speed approximately three stops faster. The image stabilizer is activated within 0.5 seconds of pressing the shutter button halfway, allowing the user to capture decisive moments.
The EF70-300mm f/4.5-5.6 DO IS USM has two image stabilizer modes. Mode 1 is effective for stationary subjects and mode 2 is best for panning with a moving subject.
Feature 4: Lens coating optimized for use with digital SLR cameras
The EF70-300mm f/4.5-5.6 DO IS USM features lens coatings optimized for use with digital SLR as well as film SLR cameras.As a result, the lens successfully realizes both appropriate color balance and minimization of ghost and flare attributable to surface reflections from the digital imaging element.
Feature 5: Zoom ring locking mechanism
When the lens is mounted on a camera that is carried on a neck or shoulder strap, the lens points downwards and the zoom elements in the lens may extend under their own weight. This can lead to damage to the lens from knocking into objects. The EF70-300mm f/4.5-5.6 DO IS USM has a locking zoom ring that keeps the lens at its shortest overall length when it is being carried. The zoom ring position is locked by sliding the zoom ring lock lever on the side of the lens.
Other features
• Silent, high-speed AF
The ring-type ultrasonic motor (USM) and rear focusing system contribute to silent, high-speed autofocus (AF) performance
• Manual focusing enabled even in AF mode
The EF70-300mm f/4.5-5.6 DO IS USM incorporates full-time manual focusing that allows users to manually focus after one-shot AF operation without leaving AF mode.
• Circular aperture for attractive boke effects
The lens aperture remains virtually circular from wide open to about two stops down, providing attractive blur effects (boke).
• Environmentally friendly lead-free glasses
The optical system contains only environmentally-friendly lead-free glasses.
This issue of the Technical Report introduces two high-performance zoom lenses. Table 1 depicts the depth-of-field data for the EF28-300mm f/3.5-5.6L IS USM and EF70-300mm f/4.5-5.6 DO IS USM. Table 2 provides the major specifications of each lens.
Table 1 Depth-of-Field Data
Table 2 Major Specifications
| EF28-300mm f/3.5-5.6L IS USM |
EF70-300mm f/4.5-5.6 DO IS USM |
||
| Focal Length / Aperture Ratio | 28-300mm f/3.5-5.6 | 70-300mm f/4.5-5.6 | |
| Lens Construction | 23 elements in 16 groups | 18 elements in 12 groups | |
| Angle of View | Diagonal | 75°- 8°15' | 34°- 8°15' |
| Vertical | 46°- 4°35' | 19°30'- 4°35' | |
| Horizontal | 65°- 6°50' | 29°- 6°50' | |
| Minimum Focusing Distance | 0.7m (at all zoom focal lengths) |
1.4m (at all zoom focal lengths) |
|
| Maximum Magnification / Field of View |
0.3x | 0.19x | |
| 100mm x 150mm (at 300mm) | 123mm x 183mm (at 300mm) | ||
| Minimum Aperture | f/22-38 (f/22-40 in cameras with 1/3 stop display) | f/32-38 (f/32-40 in cameras with 1/3 stop display) | |
| Filter Size (dia.) | 77mm | 58mm | |
| Maximum Diameter x Length | 92 x 184mm |
82.4 x 99.9mm | |
| Weight | 1670g
(Lens body only, 1840g with tripod mount) |
720g | |
| Extender | Not compatible | Not compatible | |
| Extension Tube | EF12 II | Compatible (Magnification: 0.04x - 0.50x) |
Compatible (Magnification: 0.04x - 0.26x) |
| EF25 II | Compatible at Tele (Magnification: 0.09x - 0.50x) |
Compatible (Magnification: 0.09x - 0.46x) |
|
| Close-Up Lens | 250D | Not compatible (No compatible size) |
Compatible (Magnification: 0.29x - 1.18x) |
| 500/ 500D |
Compatible (Magnification: 0.06x - 0.58x) |
Compatible (Magnification: 0.14x - 0.65x) |
|
| Gelatin Filter Holder | III | Not compatible | Compatible (max. of 4 hoods can be used) |
| IV | Compatible at Tele (max. of 6 hoods can be used) |
Compatible (max. of 4 hoods can be used) |
|
| Hood | EW-83G (Scalloped) | ET-65B (Cylindrical) | |
| Lens Case | LZ1324 | LP1116 | |
| Tripod Mount | C(W) | — | |
| Price | 346,500 yen (including hood and lens case, tax included) | 182,700 yen (including hood and lens case, tax included) | |