Canon EF Lenses manual Image Stabilizer, Circular Aperture, AF Stop Feature, Floating System

Image Stabilizer

No matter how great the lens is, camera shake can spoil the shot. Blurred photos due to camera shake usually occur when the shutter speed is slower than the reciprocal of the lens focal length. For example, a shutter speed slower than 1/200 sec. at the 200mm focal length can invite a blurred photo caused by camera shake. In such cases, a tripod is necessary. However, a tripod can be a heavy and troublesome burden when you go hiking or traveling. There are even places where using tripods is prohibited. Using a slow shutter speed then becomes difficult. To resolve this problem, Canon became the first manufacturer to incorporate an Image Stabilizer in an SLR camera lens. Optical shake is detected by gyro

With Image Stabilizer on

Circular Aperture

Certain Canon lenses feature a new Circular Aperture diaphragm unit, which uses curved aperture blades to provide for a more rounded opening as the lens is stopped down. It’s especially effective at rendering out-of-focus background highlights as natural rounded shapes. In lenses such as the EF 70-200mm f/2.8L IS lens, the lens opening is virtually circular from f/2.8 to f/5.6. These lenses retain all the benefits previously available with Canon’s Electromagnetic Diaphragm

—smooth and consistent stop-down operation (even at up to 10 fps with the EOS-1v), near-silent aperture control, and total absence of mechanical levers or switches in the lens mount.

AF Stop Feature

AF stop is featured on the EF 300mm f/2.8L IS USM, EF 400mm f/2.8L IS USM, EF 500mm f/4L IS USM, and EF 600mm f/4L IS USM lenses. If something passes between the camera and subject during autofocusing, pressing the AF stop buttons momentarily locks the AF to prevent the focus from shifting to the obstruction passing by. After the obstruction is gone, the focus is still maintained on the subject and you can quickly resume shooting. The AF stop buttons are positioned at four locations around the lens grip at the front of the lens for easy access during both horizontal and vertical shooting.

sensors which provide the data necessary to shift the image-stabilizing lens group in parallel to neutralize the shake. This increases the usable shutter speed range by up to 2 full steps for hand-held shooting. Except for the EF 28-135mm f/3.5-5.6 IS USM and EF 75-300mm f/4-5.6 IS USM lenses, IS lenses have two IS modes. One is for normal image stabilization and the other is for panned shots. With a monopod, the Image Stabilizer on all IS lenses operates normally as during hand-held shooting. Also, the EF 300mm f/2.8L IS USM, EF 400mm f/2.8L IS USM, EF 500mm f/4L IS USM, and EF 600mm f/4L IS USM lenses have a mechanism that prevents having the Image Stabilizer turned on while the lens is mounted on a tripod.

1: No camera shake

Group 1 (focusing group)

Group 2 (image-stabilizing group)

Film plane

To
Object	Group 3 to 6

2: Lens front shakes downward

With Image

Stabilizer off

Floating System

Ordinary lenses are designed to give the best results when the correction of aberrations is most effective. This is usually at the most commonly-used focusing distances. At other focusing distances, especially at the closest focusing distance, aberrations tend to appear. Canon’s floating system suppresses aberrations at close focusing distances. This system adjusts the gap between certain lens elements in correspondence to the focusing distance. The aberration is effectively corrected. The result is high image quality with aberrations suppressed at all focusing distances.

TS-E 24mm f/3.5L Floating System

Film plane

Closest shooting distance

Floating

Full-Time Manual Focusing

Canon EF lenses and EOS cameras have very high AF precision. Optimum focus can be achieved quickly for almost any shooting situation. Recent EOS cameras have been equipped with multiple focusing points for higher flexibility in composing a photo while using AF. Picture-taking is even more flexible with Canon’s full-time manual focusing which overrides the autofocusing mode. Lenses with this feature allow you to switch to manual focusing even in the AF mode. You can keep looking through the viewfinder and touch up the focus manually without switching the focus mode switch. Since the focusing ring does not rotate during autofocusing, we could make it wider for better holding comfort and easier manual focusing. Another ergonomic design which lets you convey your intentions quickly. Full- time manual focusing comes in two types. One is electronic manual focusing where the rotation amount of the focusing ring is detected and the focusing motor is driven electronically. The other type is mechanical manual focusing where the rotation of the focusing ring adjusts the focus mechanically.

Dust- and Water-Resistant Construction

The new EF 300mm f/2.8L IS USM, EF 400mm f/2.8L IS USM, EF 500mm f/4L IS USM, and EF 600mm f/4L IS USM lenses are highly dust- and water- resistant. The switch panel, exterior seams, and drop-in filter compartment have rubber linings. Moving parts such as the focusing ring and switches are also designed to prevent water and dust from entering. These lenses can therefore be used in harsh conditions without dust and water getting inside.

The lens is equipped with a rubber ring on the mount to improve its dustproofing and waterproofing characteristics. As the lens is repeatedly mounted and detached, the rubber ring will leave fine abrasion marks on the outside of the camera mount. This will not affect operation.

3:Image-stabilizing group counteracting downward camera shake

Floating Effect (TS-E 24mm f/3.5L)

Direction of Group 2 movement

How the Image Stabilizer Works in the EF 75-300mm f/4-5.6 IS USM

Astigmatism

Floating System

Input pulse board for electronic manual focusing

	Ring 1
Manual focus ring	Roller Roller	Rotor	USM Unit
	Ring 2	Stator
Focus key		Pressing spring

Focusing lens group Focusing unit

Full-time mechanical manual focus mechanism

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