Is pincushion distortion related to the diameter of the lens elements or is it corrected by type/number of lens elements?

I recently noticed this aberration with a newly purchased 1980s 35mm f/2.8 focal length lens. The vertical edge of a door was slightly bowed by pincushion distortion. The subject to camera distance was 6 - 8 feet at f/8 or 11. The lens contruction is 5/5. The aberration is also observed if shooting building columns at infinity.

This lens was reduced from a filter size of 55mm to 49mm in the early 80s. The 1960s focal length version was a 7/6 construction which perhaps is better corrected for this problem.

Your educated comments may prevent me from wasting money on an older lens.

-- Richard Jepsen (rjepsen@mmcable.com), April 28, 2001

Answers

"Is pincushion distortion related to the diameter of the lens elements or is it corrected by type/number of lens elements?"

I'm not a lens designer, but distortion is just a product of poor lens design. Adding more elements doesn't necessarily improve it. Nor does increasing the diameter of the front element.

35mm lenses are an easy type to design without distortion, unless this is for a medium format camera. Just what lens is this?

-- Jim Strutz (jimstrutz@juno.com), April 30, 2001.

I take it the distortion carries through to the print, and isn't just an effect of the viewfinder?
Pincushion distortion is unusual in wide-angle lenses. These lenses generally suffer from barrel distortion if anything. Are you sure that edges bow inward, not outward?
Anyway, the size of the front element and the maximum aperture have absolutely nothing to do with distortion. The worst offenders for distortion are zoom lenses, and these sometimes have enormous front elements relative to their small maximum aperture. In addition, stopping down has no effect on distortion either.
Factors that affect lens distortion the most, from a design viewpoint, are the retrofocus or telephoto ratio, and the positioning of the stop within the lens.
I have an old 20mm Flektogon from the 1960's that hardly shows any distortion. Today, with improved glasses available, there's no excuse at all for distortion in a prime lens of 35mm focal length, and there wasn't in 1980.

-- Pete Andrews (p.l.andrews@bham.ac.uk), April 30, 2001.

I use a very old AI-Nikkor 35mm which doesn't have any of this mistakes. As said above, it may be a poor lens design. Those lens mistakes are normal with 24 or 20mm. The diameter of the front element has no function to distortion. As larger the front element as more you shall take care of the sun. Distortion is one of the seven lens mistakes but with 35mm it shall not be a problem. May be this is a bit of help. Regards, Ralf.

-- Ralf Grambrock (ralfgrambrock@nexgo.de), April 30, 2001.

Ooops, I looked at the 6x8 enlargements and the curve is inward so it barrow distortion. The aberration is evident on a close-up, 6 ft from a door with a vertical edge and an infinity focus of columns. Once you see this, it is very ugly.

-- Richard Jepsen (rjepsen@mmcable.com), April 30, 2001.