Until now there have been few 200mm-plus telephoto zooms to choose from in the L series. In response to strong demands from customers, we developed the EF 70-300mm f/4-5.6L IS USM (Photo 1), which offers the premium performance and convenient operation of an L-series lens while satisfying price and convenience needs. The following sections detail the main features of the lens.

The lens features six-group zoom construction with 19 elements in 14 groups. UD lens elements have been placed in lens groups 1 and 3. The lens successfully eliminates almost all zooming related chromatic and other aberration fluctuations by using multiple lens groups— consisting of groups 1, 3, 4, and 6 — for zooming (figures 1 and 2).

The new model employs "inner floating focusing", in which lens group 6 serves as the main focusing lens group and lens group 4 provides focusing assistance. This floating focusing arrangement enabled us to shorten the minimum focusing distance to just 1.2 meters.

The lens has been specifically designed to thoroughly cut flare and ghosting, the two most common criticisms of previous models voiced by professional photographers. All details of both the optical and mechanical design were reconsidered from this perspective to ensure that the lens captures clear images in all kinds of adverse shooting, based on real world shooting conditions that pros face.

We managed to reduce the minimum focusing distance, which was 1.5 meters on previous models, to just 1.2 meters without compromising performance, so that photographers can take a step closer to the action. This was accomplished with the floating architecture, mentioned above, where two element lens group 4 moves as necessary while focusing to negate aberration fluctuations.

The image stabilizer on this lens works by shifting the second lens group (elements 4, 5, and 6) perpendicularly to the optical axis to counter camera shake. A super-low-friction design has been developed for the moving parts of the IS optics using bearing balls and a V-shaped groove so that the parts move by rolling friction instead of sliding friction. Another innovation was the use of a miniature stepper motor in the IS optics' locking mechanism. By incorporating technologies like these developed over the years with our IS lens series, and employing a control algorithm tuned for the IS unit's architecture and characteristics, the image stabilizer has been made compact while delivering dramatic stabilization gains equivalent to about four f-stops^*1 of shutter speed.

Professional photographers can quickly set the lens to suit their needs with the Stabilizer Mode switch on the switch panel, which gives two stabilization options: Mode 1, for image stabilization in ordinary shooting conditions, and Mode 2, which stabilizes for movement in one direction only to allow panning shots.

A mechanism that prevents accidental operation when the lens is mounted on a tripod makes it possible to shoot with a tripod while leaving image stabilization on. The lenses' image stabilization function is effective against even slight camera shake or other vibrations during tripod shooting.^{*2, *3, *4}

• *1. Image stabilization generally reaches its effective limit at a shutter speed of about [1/focal length] seconds.
• *2. Image stabilization is most effective at shutter speeds between 1/25 of a second and one second.
• *3. Image stabilization has no discernable benefit on images taken at shutter speeds slower than one second.
• *4. In certain conditions, depending on the tripod type or camera, there may be less blurring in the resulting photograph when the image stabilization function is off.

The key consideration for the lens's mechanical construction was to make it more durable than previous models by strengthening the lens barrel components and improving the construction of component connections. To allow the lens to be used in harsh conditions, the front element and the linear-drive barrel, which extends as the lens zooms, as well as the mount, switch panel, zoom ring, and focusing ring have been sealed to prevent water or dust from getting inside the lens.

The Focus Mode switch and other switches on the side switch panel have been given a lower profile to prevent unintended switch movements.

The newly developed C (WII) tripod mount ring, which is sold separately, can be used.

The lens's conventional electro-magnetic diaphragm unit forms a circular aperture that produces natural and symmetrical circular bokeh (blurring effects). Polarizing filters and other accessories can be mounted and used without any restrictions because the lens's front element does not rotate when zooming or focusing.

The new cylindrical ET-73B hood attaches to the EF 70-300mm f/4-5.6L IS USM with a two-pronged bayonet mount. The hood's inner wall is flocked for excellent anti-reflective performance.

This month's feature product, the EF 70-300mm f/4-5.6L IS USM, was field tested extensively at recent sporting events around the world, and many of our testers raved about the lens.

The EF 70-300mm f/4-5.6L IS USM is a high-performance L-series telephoto zoom that offers both superb cost effectiveness and convenience. We're certain it will become one of your favorite creative tools.