A focus tracking zoom lens is necessary for any application where live images are required, or you need constant focus within a range of distances. Zoom tracking involves the automatic adjustment of focus in response to zoom movements for the purpose of keeping an object of interest in focus. A focus tracking zoom lens is designed to maintain focus at any point within its focal length range. Zoom tracking is important when users want their subjects always in sharp focus even when they are zooming in or out. A tracking zoom lens does not require auto focus once tracking is set and a well-designed tracking zoom will maintain good resolution and focus throughout the zoom range.
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