Ultrahigh image quality L-series zoom lens ideal for use with both digital and silver-halide SLR cameras

EF24-70mm f/2.8L USM EF16-35mm f/2.8L USM

The first Technical Report of 2003 introduces the EF24-70mm f/2.8L USM, a new L-series standard zoom lens released in November 2002 together with the EOS-1Ds digital single-lens reflex (SLR) camera. In addition, it provides information on the EF16-35mm f/2.8L USM, an ultra-wide-angle zoom lens which was released in December 2001 and has received high marks ever since.

Photo 1 EF24-70mm f/2.8L USM

EF24-70mm f/2.8L USM Concept of development The EF24-70mm f/2.8L USM (Photo 1) is a L-series zoom lens with a large f/2.8 maximum aperture, developed as the successor to the EF28-70mm f/2.8L USM. The concepts of development are as follows: • Expanded zoom range with a wide-angle focal length of 24mm • Ultrahigh image definition • Ideal even with digital cameras • Higher-speed AF than its predecessor • Dust- and water-resistant construction Feature 1: Standard zoom lens with ultrahigh image quality 24mm focal length for wider-angle shooting The optical system of the EF24-70mm f/2.8L USM is based on the reputable EF28-70mm f/2.8L USM, but incorporates new design features that give a wider 24-70mm zoom range while improving on the superb image quality. The EF24-70mm f/2.8L USM uses rear focusing zoom optical system with a six-group construction and five moving groups. Focusing is accomplished by the fifth group. With its 24mm wide-angle focal length, the lens ensures wide-angle shooting not only with conventional silver-halide SLR cameras but also with digital SLRs that have imaging element dimensions of the Advanced Photo System C size. Ultrahigh quality image-the trademark of the L-series The optical system, comprised of 16 elements in 13 groups (see Fig. 1), uses a two types of aspherical lenses-conventional (ground & polished) glass and glass molded (GMo)-which eliminates aberration during zooming.

Fig. 1 Optical System Structure of EF24-70mm f/2.8L USM

Also, the use of a UD (ultra-low dispersion) glass lens in the twelfth element minimizes the lateral chromatic aberration that tends to occur at wide-angle focal lengths. The result is high quality images with excellent resolution and high contrast throughout the entire zoom and focusing range (see Fig. 2), results which can be expected only with L-series lenses.

Fig. 2 MTF Characteristic Charts of EF24-70mm f/2.8L USM

Thick lines: 10 lines/mm; thin lines: 30 lines/mm. The darker black lines represent the MTF characteristics at maximum aperture; the lighter lines represent the characteristics at f/8. The solid lines trace the radial S (sagittal) curve, while the broken lines trace the tangential M (meridional) curve.

Minimum focusing distance of 0.38 meters A minimum focusing distance of 0.38m, the shortest in its class, through the entire zoom range was achieved by increasing the power of the focusing lens group. It also gives a maximum magnification of 0.29x at 70mm telephoto (83mm x 122mm field of view). Optimized coatings considering use with digital SLR cameras The lens features optimized multi-layer optical coatings in consideration of its use with a digital SLR camera. As a result, the EF24-70mm f/2.8L USM successfully realizing both appropriate color balance and effective reduction of the ghosting attributable to surface reflections from the imaging element. Circular aperture for attractive out-of-focus effects The lens incorporates newly designed EMD (electromagnetic diaphragm) that has a circular aperture and ensures the aperture to remain virtually circular from f/2.8 to f/5.6, providing attractive out-of-focus effects (boke) that only a large aperture lenses can achieve. Feature 2: Silent, high-speed AF In addition to the silent ring-type ultrasonic motor (USM) and rear focusing by the lightweight fifth lens group, the autofocus (AF) algorithm is improved, resulting in even faster AF speed than its predecessor EF28-70mm f/2.8L USM. Feature 3: Excellent dust- and water-resistance By using dust- and water-resistant construction (see Fig. 3) in the lens mount, switch panel, zoom ring, focusing ring and the zooming extension areas to prevent dust and water from reaching the interior, the lens can be used in harsh environments.

Fig. 3 Dust- and Water-Resistant Construction of EF24-70mm f/2.8L USM

Feature 4: Outstanding operational ease Allows manual focusing even in AF mode The EF24-70mm f/2.8L USM incorporates full-time mechanical manual focusing that allows manual focusing after one-shot AF operation without leaving AF mode. Easy-to-operate, wide zoom and focusing rings A wide rotating zoom ring enables fine-tuning of composition, and the wide focusing ring allows delicate adjustment of manual focusing. Non-rotating filters Since the filter mounting thread does not rotate while zooming or focusing, it facilitates use of circular PL (polarizing) and gelatin filters. Note: Both gelatin filter holders III and IV can be used at telephoto. Hoods cannot be used as vignetting may occur. Dedicated large scalloped hood with superb light blocking The EW-83F, a dedicated large removable scalloped hood, has a superior antireflection flocking on the inner wall. It is highly effective in keeping unwanted light out of the lens. Secure hood attachment is assured by the clearly audible click when the hood is properly attached. Feature 5: Environmentally friendly lead-free glasses Giving careful consideration on the environment, the optical system of the EF24-70mm f/2.8L USM contains only lead-free glasses. Others Major specifications of the EF24-70mm f/2.8L USM are shown in Table 3. The EF24-70mm f/2.8L USM is larger than its predecessor EF28-70mm f/2.8L USM by only 6 mm in length and 70g heavier. Table 1 Depth-of-Field Data for EF24-70mm f/2.8L USM

Photo 2 EF16-35mm f/2.8L USM

EF16-35mm f/2.8L USM Concept of development The EF16-35mm f/2.8L USM (Photo 2) is a L-series ultra-wide-angle zoom lens with a large f/2.8 maximum aperture, developed as the successor to the EF17-35mm f/2.8L USM. The concepts of development are as follows: • Expanded zoom range with a wide-angle focal length of 16mm • Ultrahigh image definition • Ideal even with digital cameras • Higher-speed AF than its predecessor • Dust- and water-resistant construction Feature 1: Ultra-wide-angle zoom range The optical system of the EF16-35mm f/2.8L USM is based on the reputable EF17-35mm f/2.8L USM, but incorporates new design features that give the widest wide-angle range in its class while improving on the superb image quality. The EF16-35mm f/2.8L USM uses inner focusing optical system with a five-group construction and four moving groups. Focusing is accomplished by the second group. With its 16mm wide-angle focal length, the lens ensures wide-angle shooting not only with conventional silver-halide SLR cameras but also with digital SLRs that have imaging element dimensions of the Advanced Photo System C size. Effective angle of view is equivalent to a focal length range of 25.6mm - 56mm when the lens is used with the EOS D60 digital SLR camera. Feature 2: Ultrahigh image quality Ultrahigh quality image-the trademark of the L-series The optical system, comprised of 14 elements in 10 groups (see Fig. 4), uses a three types aspherical lenses-conventional (ground & polished) glass, replicated and glass molded (GMo)-for the first time in an EF-series interchangeable lens. This eliminates aberration during zooming while achieving ultra-wide-angle zoom range of 16mm - 35mm.

Fig. 4 Optical System Structure of EF16-35mm f/2.8L USM

Also, the use of a UD glass lens in the tenth and thirteenth elements minimizes the lateral chromatic aberration that tends to occur in wide-angle zoom lenses. The result is high quality images with excellent resolution and high contrast throughout the entire zoom and focusing range (see Fig. 5), results which can be expected only with L-series lenses.

Fig. 5 MTF Characteristic Charts of EF16-35mm f/2.8L USM

Thick lines: 10 lines/mm; thin lines: 30 lines/mm. The darker black lines represent the MTF characteristics at maximum aperture; the lighter lines represent the characteristics at f/8. The solid lines trace the radial S (sagittal) curve, while the broken lines trace the tangential M (meridional) curve.

Minimum focusing distance of 0.28 meters By increasing the power of the focusing lens group, the minimum focusing distance is shortened from 0.42m with the EF17-35mm f/2.8L USM to 0.28m, the shortest in its class, over the full zooming range. It also gives a maximum magnification of 0.22x at 35mm telephoto (108mm x 163mm field of view). Optimized coatings considering use with digital SLR cameras Thanks to its optimized coatings, the ghosting attributable to surface reflection from the imaging element is reduced to a minimum. It also helps attaining proper color balance. Circular aperture for attractive out-of-focus effects The lens incorporates newly designed EMD (electromagnetic diaphragm) that has a circular aperture and ensures the aperture to remain virtually circular from f/2.8 to f/5.6, providing attractive out-of-focus effects (boke) that only a large aperture lenses can achieve. Environmentally friendly lead-free glasses Giving careful consideration on the environment, the optical system of the EF16-35mm f/2.8L USM contains only lead-free glasses. Feature 3: Silent, high-speed AF By using a silent ring-type ultrasonic motor (USM) and inner focusing by the strengthened second lens group, the EF16-35mm f/2.8L USM has achieved even faster AF speed than its predecessor EF17-35mm f/2.8L USM. Feature 4: Excellent dust- and water-resistance Dust- and water-resistant construction (see Fig. 6) in the lens mount, switch panel, zoom ring and focusing ring to prevent dust and water from reaching the interior, the lens can be used in harsh environments. Attaching a filter to the front of the lens is recommended to attain maximum dust- and water-resistance.

Fig. 6 Dust- and Water-Resistant Construction of EF16-35mm f/2.8L USM

Feature 5: Outstanding operational ease Drop-in, gelatin filter holder provided at the rear A drop-in gelatin filter holder is provided at the rear of the lens. The holder can accommodate up to three 31mm x 31mm gelatin filters, allowing the user to add filtering effects. Full-time manual focusing mechanism The EF16-35mm f/2.8L USM incorporates full-time mechanical manual focusing that allows manual focusing after one-shot AF operation without leaving AF mode. Non-rotating filters Since the filter mounting thread does not rotate while zooming or focusing, it facilitates use of circular PL (polarizing) and gelatin filters. Note: As the lens has an ultra-wide-angle zoom range, vignetting may occur depends on the type of circular polarizing filters used. To prevent vignetting, use Canon's 77mm PL-CII circular polarizing filter. Dedicated large scalloped hood with superb light blocking The EW-83E, a dedicated large removable scalloped hood, has a superior antireflection flocking on the inner wall. It is highly effective in keeping unwanted light out of the lens. Secure hood attachment is assured by the clearly audible click when the hood is properly attached. Feature 6: Environmentally friendly lead-free glasses Giving careful consideration on the environment, the optical system of the EF16-35mm f/2.8L USM contains only lead-free glasses. Others Major specifications of the EF16-35mm f/2.8L USM are shown in Table 3. While the EF16-35mm f/2.8L USM has achieved higher performance than its predecessor, the EF17-35mm f/2.8L USM, it is larger by only 7.3mm in length and 55g heavier. Table 2 Depth-of-Field Data for EF16-35mm f/2.8L USM This issue of the Technical Report introduces two L-series interchangeable zoom lenses. Tables 1 and 2 depict the depth-of-field data under each condition.

Table 3 Major Specifications

EF24-70mm f/2.8L USM EF16-35mm f/2.8L USM Focal Length/ Aperture Ratio 24-70mm f/2.8 16-35mm f/2.8 Lens Construction 16 elements in 13 groups 14 elements in 10 groups Angle of View Diagonal 84°-34° 108°10’-63 Vertical 53°-19°30’ 74°10’-38° Horizontal 74°-29° 98°-54° Minimum Focusing Distance 0.38m (at all zoom focal lengths) 0.28m (at all zoom focal lengths) Maximum Magnification/ Field of View 0.29x, 83mm x 122mm 0.22x, 108mm x 163mm Minimum Aperture f/22 f/22 Filter Size ø77mm ø77mm Maximum Diameter/ Length ø83.2mm x 123.5mm ø83.5mm x 103mm Weight 950g 600g Hood EW-83F EW-83E Lens Case LP1219 LP1319 Price 220,000 yen (including hood case, tax not included) 230,000 yen (including hood case, tax not included)