[rollei_list] Re: Lens recommendation
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Sun, 1 Aug 2010 17:55:31 -0300
2010/8/1 Elias_Roustom <elroustom@xxxxxxxxx>:
> What is the significance of the APO designation. I see lots of Rodagon
> lenses without the APO.
The German standards "D.I.N" definition for an Apochromatic lens is
that the lateral chromatic aberrations of the secondary spectrum are
reduced to within a minute percentage of the focal length of the lens,
it's the main reason several German lenses have the APO designation,
some Japanese lenses also use this designation. The DIN definition
looks different regarding the traditional Apochromatic definition,
basically: "Apochromat: A lens in which light of three colors is
brought into common focus", PHOTOGRAPHIC OPTICS by Arthur Cox 15th
edition 1974.
And then if you take the traditional definition, most APO lenses are
not Apochromatic, the German lenses like the Apo Rodagon, Apo Sironar
and most others "Apo" are Apochromatic according the DIN definition,
the DIN definition looks more "tolerant" regarding the traditional
definition. Some tests about these DIN Apochromatic lenses show they
are not Apochromatic for the term traditional definition.
Elias, I live within a sub-tropical area and fungus can't develope a
web so quickly IMO, perhaps your lens already had little white points
that became web. I read Olympus and Zeiss and Schneider
recommendations to prevent them: Silica Gel, to change the air around
your lens often and to allow them to receive the bright sunlight
regularly
Carlos
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