Autofocus
Like the EOS 500D, the EOS 550D has nine AF points arranged in a diamond around the centre of the image frame, with the central point being the f/5.6 cross-type that is extra sensitive at f/2.8. Having nine points rather than the 19 of the EOS 7D means that there’s a reduced chance of the subject falling directly under one of the rectangles in the viewfinder. For photographers like me who were brought up using the focus-and-recompose technique, this isn’t a major issue when the camera is handheld and shooting stationary objects.
When the camera is on a tripod the tendency is to compose the image and then get the focus spot-on, and unless there is an AF point in just the right place it may be necessary to move the camera to focus and readjust the composition. Alternatively, there is the option to focus manually. With a high-resolution, Live View-enabled LCD screen, my inclination is to compose the image on the monitor and use the magnified views (5x and 10x) to ensure the subject is sharp. However, in bright ambient light some shading is required to give a clear view of the subject detail.
Not unusually, the AF performance in any particular lighting situation can vary depending upon the lens mounted. With the EF-S 18-55mm f/3.5-5.6 IS kit lens, autofocusing is reasonably quick and accurate in decent light, but when light levels fall or the subject’s contrast is low it can become a little slower and more hesitant.
However, with a high-quality optic like the EF 24-70mm f/2.8 L USM or EF 70-200mm f/4 L USM it is speedy and decisive. I was impressed by how small a detail the AF system could latch on to. Furthermore, when the continuous AF option is selected, the camera does a good job of tracking a moving subject under the AF point.The EOS 550D doesn’t have the same options to adjust the speed of the continuous AF response as the EOS 7D. For most novice photographers this would be an unnecessary complication, but for sports enthusiasts it may be a disappointment.
