Does anybody have information on rapid rectilinear lenses? I understand the design is an early one (pre-1900) and that they degrade in sharpness before they vignette. Any info on specific brands, focal lengths, coverage, etc.? Also interested in specific info on elements, groups, etc.

Thank

-- Dave Willison (dwillisart@aol.com), February 25, 2001

Answers

Dave: According to a book I have, published in 1943, The rapid rectilinear lens was designed in 1866 by Dallmeyer and at the same time by Steinheil. It is a four element lens, with identical front and rear cell being made up of two cemented elements. Aperature was f- 8 and the lens had a 50 degree angle of view. The article states that above 50 degrees anastigmatism becomes unbearably great. The lens was the first attempt to spherically correct a lens so that larger aperatures could be used. At that time, f-8 was considered a large aperature. I can't help with the specific brands, because just about every company made the design, nor can I help with focal lengths. I'm sure there are those on this forum with this information.

Regards,

-- Doug Paramore (dougmary@alaweb.com), February 25, 2001.

Weston used one when it had become outmoded by the latest soft-focus lenses.

It is fairly common for lenses of that vintage to have a wider circle of coverage than is usable. Modern lenses are designed to vignette to improve contrast that would be lowered by excessive internal reflections, and to generally improve the sharpness specs of the lens. If you prefer soft corners and wider coverage to less coverage black corners, older lenses can be preferable in some respects to newer ones.

-- David A. Goldfarb (dgoldfarb@barnard.edu), February 25, 2001.