olyacme wrote: thrice wrote:
The Cosina-Voigtlander 180/4 APO-Lanthar has no perceivable CA at least at any aperture across the entire frame. The Leica 100mm APO-Macro-Elmarit-R is almost as well corrected.
Unless a reviewer had access to a 135 sensor with no AA filter and 160MP (or more likely a smaller sensor they can move about on the focus plane), they won\'t have been able to tell whether it was Apochromatic at f/4.0 or not. I didn\'t pull that number of MP out of thin air, either, which should put the Apo at f/2.5 (try 300MP) thing into better perspective.
Even on an attainable sensor, and at a reasonable f-stop, the lack of CA does not alone make a lens Apochromatic. The lens must also be multiply corrected for Spherical Aberration, and, by most definitions, Coma. Even with all that, we\'re only getting started making a nice lens.
Too busy ranting and speaking down to others with the assumption you know more about optics than they do to read posts properly?
I said \"perceivable chromatic aberration\". For colour photographs longitudinal and transverse CA as well as coma are the aberrations most likely reduced with a so-called APO lens, which is the whole point for us. Provided the majority of the airy discs are below the nyquist frequency of the chosen medium then what is the problem? The AA filter argument is moot with any reasonable photographer, it\'s suitably weak enough on modern cameras.
Have you used either of the lenses I mentioned? I\'m shooting on a 5D Mark II, for 35mm only the D3x and Sony A900 (at low ISO\'s) is more demanding. Maybe there\'s a 25 speed film with more extractable detail but for the purposes of measuring CA and coma digital tends to be very unforgiving to most lenses. With a film scanner you can introduce your own aberrations at that kind of (130mp) magnification with their optics.
I never said these lenses were apochromatic across the entire visible and near visible spectrum. Even the coastal optics 60/4 isn\'t quite that well corrected although it comes very close, I assume you use that one since you consider the Voigtlander 180/4 and Leica 100/2.8 not nice lenses?
Jul 22, 2009 at 09:50 AM
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