FEATURED WEB TUTORIAL: FOCUS LOCK
Autofocus Lock Explained
Published by: ePhotozine
All autofocus cameras use either subject contrast or infrared detection to determine the subject's distance from the camera. The trouble is, although technically highly advanced, they can still easily be fooled. Your autofocus camera will have either passive or active autofocus, in simple terms passive uses electronics that can measure subject contrast to determine the distance, while active fires out an infrared beam to measure the distance. Unless the camera is one of the newer models with a wide area AF or multi point focus, the subject has to be in the centre of the frame and here's the downfall, and one reason why you may have got back blurred photos from your holiday or special occasion. If you take a photo with the subject off-centre the camera will focus on whatever is in the background. If this is a similar distance your shot will be safe, but often it's much further away and the camera adjusts focus to the background. The result is a blurred subject in front of a razor sharp background.