Zoom lens design is inherently more complicated than is the design of fixed-focus lenses, and workers have traditionally been faced with a staggering amount of labor before the design is complete. One must calculate the first-order properties and the motions of the several lens groups while correcting image aberrations at many points in the zoom, over the field, in many colors, while keeping the image size and location stationary. That is not easy. The process was difficult, tedious, and often frustrating.
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