Relating to my thread about Pentax making a rectilinear 35mm, I have done some investigation in the area of distortion. It seems that a single negative element will cause barrel distortion and a positive element will cause pincushion distortion. The major difference between a fisheye and rectilinear lens of the same focal length is the ratio of positive and negative elements. The rectilinear ones will generally have about 35-50% negative and the fisheyes will have at least half being negative. That many negative elements is what gives the fisheye so much barrel distortion. Pentax could easily make a rectilinear 35mm lens for the 67. SR

-- Steve Rasmussen (srasmuss@flash.net), May 11, 1999

Answers

In addition to the above reasons for distortion, I have also seen the affect of spherical aberration on distortion. The two are closly related. Aspherical surfaces(elipsoidal, hyperboloidal)can be used to control distortion as well as spherical aberration. SR

-- Steve Rasmussen (srasmuss@flash.net), December 06, 1999.

this is actually a question... i was wondering if anyone has experience using rectilinear and fisheye lenses in making spherical vr panoramic movies? i'm wondering which will result in a better product, pros and cons of both, that sort of thing. email me if you have any input? thanks.

-- ari moore (alm26@cornell.edu), October 17, 2001.