Canon's breakthrough multi-layer diffractive optical lens technology provides photographers with superior super-telephoto performance in a smaller and lighter design with enhanced correction for chromatic aberrations. Canon have also added an Image Stabilization system that gives the equivalent effect of a shutter speed two stops faster. Also features fast AF, full-time mechanical focus and dust and water-resistant construction.
Diffractive Optics (DO)
In terms of design and manufacture, diffractive optics allow Canon to create lenses that are shorter and lighter than comparable refractive optical systems. The 400mm f/4 DO IS USM lens is approximately 27-percent shorter and 36-percent lighter than a conventional 400mm f/4 telephoto lens would be. Image quality of a DO lens is comparable to that of an L-Series lens, offering photographers the highest performance.
Fluorite (CaF2) Glass lens element
Fluorite has extremely low indexes of refraction and dispersion compared to optical glass. It features special partial dispersion characteristics (extraordinary partial dispersion), enabling virtually ideal correction of chromatic aberrations when combined with optical glass.
Ultrasonic Motor (USM)
Features of the USM include the ability to easily achieve the low-speed, high-torque characteristics needed to realize direct drive. Large holding torque means the disc brake automatically holds the lens in place when the motor is stopped. Its construction is extremely simple, operation is virtually noiseless, and it demonstrates excellent start/stop response and control. High efficiency and low power consumption allow the lens to be powered by the camera's battery.
Rotation speed covers a wide variable range from 0.2 rpm to 80 rpm to realize high-precision, high-speed lens drive control. Variable-sensitivity electronic manual focus is also available. The broad operating temperature range of -30ºC to +60ºC (-22ºF to 140ºF) ensures stable operation even in severe environments. All lens drive control is performed by the microprocessor housed within the lens.
Full-Time Manual Focusing
This system allows the photographer to turn the manual focusing ring and instantly override the autofocus. Even when the lens is set to the autofocus mode.
The 400mm F4 DO IS allows the photographer to focus upon a subject and then memorise the focus setting. The photographer can then instantly return to that setting with a brief turn of the metal "playback" ring on the lens barrel.
A superb technology that allows the lens to sense movement from "shake" or vibrations, and instantly apply an optical correction by moving a group of lens elements. The improvement in steadiness can be seen even in the viewfinder, and most users find they can shoot hand-held or on a monopod at shutter speeds about two stops slower than previously possible and consistently get sharp images.
AF Stop Feature
One of four buttons on the outer barrel of the lens will temporarily lock the AF if the camera is in the AI Servo AF mode. Custom Functions on many newer EOS bodies allow these buttons to assume a variety of additional functions.
- Lens Hood Compatibility Fitting: ET-120
- Bag/Case size (not supplied): Lens Case 5
- Dimensions for Lenses: 128 x 232.7mm
- Weight (g) for Lenses: 1940
- Type: Fixed Focal Length
- Type: Telephoto
- Lens Fitting: Canon AF, Canon Lens Extender Compatible
- Focusing: Auto
- Filter - Size: 52mm Drop-In