[rollei_list] Re: OT: Leica vs. Zeiss
- From: Frank Dernie <Frank.Dernie@xxxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Wed, 18 Nov 2009 05:54:10 +0000
Actually Apo is a typo in the case of this lens as such an item does not exist.
The latest 50mm f1.4 is Aspherical not apo. It is by a long way the best f1.4
lens I have used wide open, and I have used a few. The new-Zeiss 50 f1.5 sonnar
is reported to be a retro lens and is soft and suitable for portraits wide
open, though I have not used one personally. Only 2 Leica M lenses are marked
Apo, the latest 90mm f2 and 135mm f3.4. I would be prepared to bet five bob
that they really are apo...
The Leica lenses I have, which is quite a few, may not all be apo, whether
marked thus or not, but they show noticeably less chromatic fringing than most
of the fast lenses I have from Nikon or Canon. FWIW.
Frank
On 17 Nov, 2009, at 23:15, Richard Knoppow wrote:
>
> ----- Original Message ----- From: "Jan Decher" <Jan.Decher@xxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Tuesday, November 17, 2009 8:53 AM
> Subject: [rollei_list] Re: OT: Leica vs. Zeiss
>
>
>> Marc,
>>
>> This is what I thought. So we should compare a current Summicron to the
>> curretn Zeiss ZM Planar perhaps (tie?) and the Apo-Summilux to the new
>> 1.5/50 Sonnar (Summilux wins, I suppose).
>>
>> I might take you up on stopping by at your house next time I am in the D.C.
>> area (X-mas?). Aren't you down there somewhere (Virginia?).
>>
>> Really ought to see that PLOOT reflex housing ;-)
>> ...and maybe you even have an original Contax OIympia Sonnar engraved by
>> Leni Riefenstahl....
>>
>> Jan
>
> I wonder if the Apo-Summilux is really an apochromatic lens. The prefix
> Apo has been used on a number of German-made lenses which are, in fact, just
> plain achromats. For a while there was something in the DIN standards that
> allowed this despite the very long use of the appellation apochromatic to
> mean a lens with longitudinal chromatic correction for three colors and
> correction for spherical aberration for two colors. The chromatic aberration
> curves for apochromatic lenses has a characteristic S shape and crosses the
> zero line (no chromatic error) in three places. An acromatic lens is
> corrected for two colors for focus and one color for spherical. In fact, a
> well designed achromat may have less deviation from focus at intermediate
> colors than a poor apochromatic lens but, in the past, most true apo's have
> been designed for special purposes, such as process work, where it was
> imperative that chromatic correction be very good.
> I don't think the term "apochromatic" has ever been officially defined for
> camera lenses but it has for microscope and telescope objectives so the term
> is very well established.
> It is possible to correct a lens for any number of wavelengths. Those
> corrected for more than three are known as superachromats. They are rare
> because they are quite expensive to make and have little advantage as general
> purpose camera lenses. Nonetheless they do exist for special purposes.
> Simply being apochromatically corrected is no guarantee of lens
> performance, there are still many other aberrations that must be well
> corrected.
> As I stated before the only way to make definite comparisons of lenses is
> to set them up on an optical bench and see what they do. If the actual
> prescription is available one can set up the design in a computer lens design
> program and analyse it. Modern programs can completely characterize a lens in
> a few seconds, an analysis way beyond what could be accomplised with hand or
> calculator assisted math in the past. Of course, the design performance may
> not be realized in an actual production lens.
>
> --
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
> ---
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