What conditions are likely to cause focusing problems?
Combinations of low light and use of the long zoom create most problems. In low light conditions, the aperture opens wide, and the depth of field is narrower. It is also narrower at extreme zoom settings. These situations can be aggravated by using the Portrait mode. Similarly, manually setting the ISO to 50 or 100 can also force a wider aperture than the camera would select if the ISO value were set at automatic. Using macro mode at wide angle very close to the subject also results in a very narrow depth of field, often limited to a few millimetres. While filters have no adverse effect, shooting through windows can sometimes confuse the system, especially when wet, dirty, or at an angle. If the focusing area includes lots of sharply defined objects at a different distance from the subject, the camera tends to focus on those instead of the subject. For instance, in this pic, the camera has focused on the leaves on the ground, rather than the flower.
