Archived posting to the Leica Users Group, 2010/03/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Now that is deep thinking! Jim Nichols Tullahoma, TN USA ----- Original Message ----- From: "philippe.amard" <philippe.amard at sfr.fr> To: "Leica Users Group" <lug at leica-users.org> Sent: Friday, March 19, 2010 5:40 PM Subject: Re: [Leica] Image circle > Is the circle really a circle when using ASPH lenses? > > Sure? > > Phx > > > > Le 19 mars 10 ? 23:34, Mark Rabiner a ?crit : > >> >>> Richard, >>> >>> The size of a lens image circle is not absolute but depends on your >>> criteria. Most lenses are sharp and relatively distortionless in the >>> center of the image. Quality and illumination fall off as you move >>> away from the axis. You have reached the edge of the lens image circle >>> when the image quality no longer meets your photographic requirements. >>> That being said, the easiest way to determine the approximate size of >>> the image circle is to hold the lens in front of a ground glass. Adjust >>> it so that it focuses a distant scene and simply measure the >>> illuminated circle on the ground glass. Most normal lenses have a >>> reasonable quality of image in a circle with a diameter approximating >>> their focal >>> length. Symmetrical lens designs tend to have a bigger image circle and >>> are frequently used for wide angle lenses. >>> Larry Z >>> >> >> >> And your image circle gets better when you work closer. >> That you learn from view camera work. >> >> [Rabs] >> Mark William Rabiner >> >> >> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information >> > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > >