When Canon created the Digital Rebel, they introduced a line of digital only lenses are called EF S series lenses. Canon digital Rebel lenses have the same physical mount and electronic coupling system, but cannot be used on older Canon digital cameras and on no Canon 35mm cameras. This is because the rear portion of EF S lenses extends deeper into the mirror chamber and damage to the mirror on older cameras can occur. Canon EF S lenses should only be used on the Canon EOS 20D, 30D and Digital Rebel series and newer models designed to be compatible with EF S lenses. Before the EOS system was introduced, Canon cameras used a different lens mounting system called the “FD” mount. These manual focus lenses had a mechanical aperture ring and cannot be used on EOS film or digital cameras.
EF S lenses specifically target the EOS 20D and Digital Rebel cameras, with optics designed to efficiently cover their compact imaging sensors. Technologies EOS users have come to expect in lenses, including Ultrasonic focusing motors, Aspherical elements, and even Image Stabilization are available throughout this new lens series. EF S lenses are yet another option for EOS digital shooters. 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 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 3 full steps for hand held shooting.
All L series, 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, all IS super telephoto lenses as well as the EF 28 300mm f/3.5 5.6L IS USM and the EF 70 200mm f/2.8L IS USM have a mechanism that shuts off the Image Stabilizer while the lens is mounted on a tripod.
Certain Canon digital Rebel 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. 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 auto focusing 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 auto focusing, we could make it wider for better holding comfort and easier manual focusing.
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.
AF stop is featured on the EF 300mm f/2.8L IS USM, EF 400mm f/2.8L IS USM, EF 400mm f/4 DO 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 auto focusing, 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.
With the focus preset feature, you can set the desired focusing distance in memory and later instantly focus the lens at that distance. Normal picture taking and focusing are possible even while focus preset has been set. At a soccer game, for example, you can preset the focus for the goal. You can focus normally while the player approaches the goal, then when the ball is shot into the goal, you can obtain instant focus.
The digital single lens reflex (SLR) has become the standard tool for serious photographers. When the Canon Digital Rebel XTi entered the market for digital SLR cameras the demand for Canon digital rebel lenses expanded tremendously. Regardless of what lens or filters are attached to the SLR, the photographer can frame images quickly and accurately. But the trade off is that the SLR is larger and heavier than the point and shoot camera. If you need a camera for everyday use or just in case something interesting pops up, point and shoot cameras are fine. If you are specifically going out to take pictures, the SLR will give you a wide range of options and controls.
