Re: [Leica] M 21mm lens question

["Henning J. Wulff" <henningw@archiphoto.com>]

At 8:45 AM -0700 17/1/01, John Collier wrote:
>I am in the middle of negotiating a deal on a NOS 21/2.8 Asph and I am
>wondering if anyone can comment on the level of distortion in the lens. I
>had a 21/3.4 and it had virtually no distortion (flare prone wide open
>though). I have heard that the 21/2.8 non-asph had a "wave" like distortion
>when focused close (Osterloh). How does the 21/2.8 perform in the distortion
>department when compared to the older lenses?
>
>Thanks,
>
>John Collier
>
>PS: Should I get a black chrome or silver chrome finished lens? ;-)

While the distortion level of the 21ASPH is higher than that of the 
SA, it is very low and not of any significance under almost any 
circumstance, including fairly stringent architectural shooting. The 
distortion level is slightly lower than that of the older 21/2.8.

This is all due basically to the fact that the 21/2.8's are 
retrofocus designs to allow TTL metering, while the SA is almost 
symmetrical. Same as the Hologon has essentially no distortion, and 
the Cosina 15 has a little. The 'wave' or 'moustache' type of 
distortion is typical of most retrofocus lenses of the last 30 years, 
which results from efforts to partially correct the intrinsic barrel 
distortion of the design.

That said, the 21ASPH has better eveness of illumination due to the 
same design parameters. I don't agree with Erwin completely on his 
comparative evaluation of the 21's, so I am keeping my 21SA for its 
performance under certain circumstances, close shooting, and for the 
absolute lowest level of distortion. However, I use the 21ASPH a lot 
more often due to its convenience.

The distortion level of the ASPH is a lot lower than that of any SLR 
lens in this range I have tried, and I have owned or used about 
20-25.

    *            Henning J. Wulff
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