John Lovda wrote:
The description of the EF 50mm f1.4 USM on the Canon USA website claims that it is a "new Gaussian" design. John Lovda > > > the new Canon 50mm F1.4 like many others is a > Planar derivative. > > > Your Nikkor 105mm F2.5 Micro is claimed to be > based on the Xenotar which is > > really a Planar-type lens (both of which are > Gaussian lenses). ---------------------------------------------------------------------------- Yes, new as in a modified version using the Gaussian lens. Gaussian means it is based on the principle discovered by C.F. Gauss that if an objective has elements separated by a small air gap having the same shape of a negative lens, the variation of spherical aberration with wavelength could be eliminated. Paul Rudolph created the Planar (in 1896) by inserting two cemented surfaces into a symmetrical Gauss-type lens. Derivatives of this type of design include (that is use of cemented surfaces in a Gauss lens) include but are not limited to Leitz Summar, Cooke Opic lens, Schneider Xenon and Xenotar, Kodak Ektar, and Zeiss Biotar. Thus the EF 50mm F1.4 is a Gaussian design sometimes also referred to as an Opic type. If you compare the diagrams of the Canon 50mm F1.4 and the Zeiss G 45mm F2 they are nearly identical. Put those next to the 35mm F2 Summicron-M and again you will see how close it is as well. Peter K * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
