Abstract
We perform two psychophysics experiments to investigate a viewer’s ability to detect defocus in video; in particular, the defocus that arises in video during motion in depth when the camera does not maintain sharp focus throughout the motion. The first experiment demonstrates that blur sensitivity during viewing is affected by the speed at which the target moves towards the camera. The second experiment measures a viewer’s ability to notice momentary defocus and shows that the threshold of blur detection in arc minutes decreases significantly as the duration of the blur increases. Our results suggest that it is important to have good control of focus while recording video and that momentary defocus should be kept as short as possible so it goes unnoticed.
Highlights
In photography, depth of field (DOF) refers to the range of depths in a scene where objects appear in focus
We present two psychophysics experiments to investigate a viewer’s ability to detect defocus in video
No previous studies have investigated blur discrimination when viewing an object moving in depth
Summary
Depth of field (DOF) refers to the range of depths in a scene where objects appear in focus. A common photographic technique is to manipulate the DOF to bring more attention to some objects than others. Such effect is likewise used in cinematography, where it is common to track an object as it moves in depth. The DOF can be in the order of centimeters when using medium length or telephoto lenses, and when filming at close distances with a wide angle lens. In these cases, focus pulling must be done with great care, as a small error can be the difference between focusing on the actor’s ears instead of their eyes
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