support autofocusing with the camera. (You should explore the lens manual for specifics, of course.)
Focusing
Set the lens to automatic or manual focusing by moving the focus-method switch on the lens, labeled in Figure 1-25. Move the switch to the AF position for autofocusing and to MF for manual focusing. Then proceed as follows:
Autofocusing: Press and hold the shutter button halfway. In Live View mode, you also have the option of tapping the touch screen to focus.
Manual focusing: After setting the focus method to MF, rotate the focusing ring on the lens barrel until your subject appears sharp in the viewfinder or on the Live View screen. The position of the focusing ring varies depending on the lens; again, Figure 1-25 shows the ring as it appears on the 18–135mm kit lens.
FIGURE 1-25: Here are a few features that may be found on your lens.
See Chapter 5 for more help with both automatic and manual focusing.
Zooming
If you bought a zoom lens, it has a movable zoom ring. The location of the zoom ring on the 18–135mm kit lens is shown in Figure 1-25. To zoom in or out, rotate the ring.
Enabling Image Stabilization
Many Canon lenses, including either kit lens, offer this feature, which compensates for small amounts of camera shake that can occur when you handhold the camera. Camera movement during the exposure can produce blurry images, so turning on Image Stabilization can help you get sharper handheld shots.
On non-Canon lenses, Image Stabilization may go by another name: anti-shake, vibration compensation, and so on. In some cases, the manufacturers recommend that you leave the system turned on or select a special setting when you use a tripod, so check the lens manual for information.
Whatever lens you use, Image Stabilization isn’t meant to eliminate the blur that can occur when your subject moves during the exposure. That problem is related to shutter speed, a topic you can explore in Chapter 4.
The angle of view that a lens can capture is determined by its focal length, or in the case of a zoom lens, the range of focal lengths it offers. Focal length is measured in millimeters. The shorter the focal length, the wider the angle of view. As focal length increases, the angle of view narrows, and the subject occupies more of the frame.
Generally speaking, lenses with focal lengths shorter than 35mm are considered wide-angle lenses and lenses with focal lengths greater than 80mm are considered telephoto lenses. Anything in the middle is a normal lens, suitable for shooting scenes that don’t require either a wide or narrow angle of view.
Note, however, that the focal lengths stated in this book and elsewhere are 35mm-equivalent focal lengths. Here’s the deal: When you put a standard lens on most dSLR cameras, including the 90D, the available frame area is reduced, as if you took a picture on a camera that uses 35mm film negatives and cropped it. This crop factor varies depending on the camera, which is why the photo industry adopted the 35mm-equivalent measuring stick as a standard. With the 90D, the crop factor is roughly 1.6x. In the figure here, the red frame indicates the portion of a 35mm frame that is captured at that crop factor.
When shopping for a lens, it’s important to remember this crop factor to make sure that you get the focal length designed for the type of pictures you want to take. Just multiply the lens focal length by 1.6 to determine the actual angle of view.
Removing a lens
After turning the camera off, press and hold the lens-release button on the camera (refer to Figure 1-25), and turn the lens toward the shutter button side of the camera until the lens detaches from the lens mount. Put the rear protective cap onto the back of the lens and, if you aren’t putting another lens on the camera, cover the lens mount with its cap, too.
Decoding Canon lens terminology
When you shop for Canon lenses, you encounter these lens specifications:
EF and EF-S: EF stands for electro focus; the S stands for short back focus. And that simply means the rear element of the lens is closer to the sensor than with an EF lens. The good news is that your 90D works with both of these Canon lens types.
IS: Indicates that the
