Pre-Focus and the Burst Window: RF 100-500mm f/4.5-7.1L IS USM
The RF 100-500mm f/4.5-7.1L IS USM is Canon’s accessible super-telephoto — L-series quality, manageable weight at 1.37 kilograms, and a zoom range that covers most wildlife and sports scenarios without a second body. The technique that makes it earn that range is not the zoom itself. It is pre-focus combined with burst discipline.
Pre-focus means acquiring focus on a known point before the decisive moment, then holding it. A bird banking toward a perch, a runner coming through a gate, a vehicle entering a corner — the trajectory is predictable. You focus on the landing point and wait. When the subject arrives, you fire a burst. You are not tracking a moving subject; you are ambushing a stationary point with a moving subject.
The R5 Mark II’s subject tracking can handle the alternative: active tracking of a moving bird or athlete. For linear motion with a clear endpoint, pre-focus is faster and produces a higher percentage of sharp frames because there is no delay between track acquisition and focus confirmation. The focus is already confirmed. You press, the camera fires at up to 30 fps in electronic shutter mode, and the subject arrives into that burst window sharp from the first frame.
The practical discipline is restraint. At 30 fps, a three-second burst is ninety frames. You do not need ninety frames. You need the ten frames during which the subject was in the right position, at the right angle, with the right wing position or expression or stride. The burst is insurance, not output. Cull ruthlessly.
At 500mm and f/7.1, depth of field is tight — roughly three to four meters at a subject distance of twenty meters. Pre-focus works here because the subject is moving toward a point you have already resolved. The focus is not uncertain; only the timing is.
Know where the subject is going. Be focused there before it arrives.