Rapid Rectilinear
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The Rapid Rectilinear also named Aplanat is a famous photographic lens design.
Aplanat photographic lens.
Rectilinear lens
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In photography, a rectilinear lens is a photographic lens that yields images where straight features, such as the edges of walls of buildings, appear with straight lines, as opposed to being curved. I
Curvilinear (above) and rectilinear (below) image. Notice the barrel distortion typical for fisheye lenses in the curvilinear image. While this example has been rectilinear-corrected by software, high quality wide-angle lenses are built with optical rectilinear correction.