Autofocus

The phase detection autofocus sensor can detect how far out of focus a subject is, and whether the lens needs to focus nearer or further – it knows the correct adjustment before it focuses

Focusing is one of those tasks that But today’s digital SLRs offer much higher levels of resolution, and the old techniques of guesswork and estimates aren’t good enough any more. We want our photographs to be razorsharp, so we need the precision and speed of a modern multi-point autofocus system.