autofocus

For aviation the mode matters more than the system: continuous autofocus with tracking, so focus follows an approaching aircraft rather than locking once. A pale aircraft against a featureless overcast sky is the case that defeats most systems, and the usual answer is to give it the higher-contrast part of the airframe to hold on to.

Nearby in Photography

• aperture — The adjustable opening in a lens that controls how much light reaches the sensor, expressed as an f-number.
• aperture priority — An exposure mode in which you set the aperture and the camera chooses the shutter speed.
• back-lit — Lit from behind, with the light source on the far side of the subject from the camera.
• blue hour — The twilight period before sunrise and after sunset when the sky is deeply and evenly blue.