jump

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Related to jump the gun: keep one's nose to the grindstone

jump

The displacement of the image of an object occurring when viewing across the borderline between two portions of different power in a bifocal or trifocal lens. The jump is eliminated by placing the optical centres on the dividing line; the lens is then called a no jump bifocal (e.g. a monocentric bifocal with a straight dividing line) (Fig. J1). Syn. image jump; prismatic jump. See monocentric.
Fig. J1 Image jump upward caused by the segment of a bifocal lens, as the direction of gaze is lowered across the dividing lineenlarge picture
Fig. J1 Image jump upward caused by the segment of a bifocal lens, as the direction of gaze is lowered across the dividing line
References in periodicals archive ?
The Windsor Park veteran fears fans might jump the gun expecting this week's UEFA Cup tie against Swedish side Halmstads to be a foregone conclusion.
But he insists the current laws - which disqualify the second runner to jump the gun in any given race - give slow starters the chance to twist the rules in their favour.
Or you can jump the gun with Joan and Melissa Rivers on the red carpet at 6 p.
It is a case of biding my time so I don't jump the gun, and not try to do too much, too early.