Zeiss Reports Highest-Ever Lens Resolution
Carl Zeiss AG, Germany, one of the oldest and most respected camera lens makers in the world, reports in Camera Lens News that it has achieved its highest-ever resolution from a camera lens.
Using a production camera and lens, along with special high-resolution SPUR-Orthopan UR film, Zeiss scientists were able to achieve 400 lp/mm on film from a Cosina-made Carl Zeiss ZM-Biogon 25mm ƒ/2.8 lens in ZM (Leica M bayonet) mount, in the center of the image field at ƒ/4. A lens that can resolve 240 lp/mm on film would be considered outstanding.
With virtually all camera lenses, common aberrations limit performance at wider apertures. Stopping the lens down reduces the effects and extent of aberrations, but introduces diffraction. By the point where diffraction dominates the degradation of the image, the lens is said to be "diffraction limited." The wider the aperture at which a lens is diffraction limited, the better the lens.
Not only is the 25mm ZM-Biogon diffraction limited at a a wide aperture, but the 400 lp/mm achieved by Zeiss is the maximum resolution theoretically possible at ƒ/4. Quite an achievement for a production camera lens.
ADDENDUM: Ever the contrarian, the thing I'm most enthused about when shooting with this lens is the totally completely incredibly wonderful finder. How's that? You know, the little viewfinder you clip into the hot shoe, the square bit seen at the top of the picture above. It is without question the best 24/25mm and/or 28mm finder this writer has ever put his jaded eye to. Just a pleasure to look at the world through. Quite addictive. To forestall the inevitable questions, no, you do not need one; yes, other finders work pretty much as well; but no, no other finder I've ever seen for lenses this wide is as clear, bright, clean, and rectilinear as this. With the caveat that it's an extra, highly recommended if you often use a 24mm or 28mm on any 35mm rangefinder camera.
Posted by: MIKE JOHNSTON