[Leica] 21mm Lens Questions

[henningw at archiphoto.com (Henning Wulff)]

At 10:05 AM -0700 9/25/07, red735i@earthlink.net wrote:
>You are correct.. it is Cosina vs Leica since all 3 lenses in 
>contention are made by Cosina.  But then you must consider that the 
>2 Zeisss lenses are basically the same $1000 price without finder, 
>but the Cosina lens is $300-500, with finder.  to boot, the 4.5 
>Biogon and the 4 Cosina look like the same optical formula.


The Biogon f/4.5 and the C/V f/4 are quite different lenses. The 
Biogon is not large, but a lot bigger than the C/V, and the 
performance is a lot different as well. In the center all the 21's 
are very good, with the ASPH the best by a good bit. As you get to 
the mid outer zones, the ASPH drops a bit until by 2/3's out the 
Biogon is just as good, and in the very outer zones a bit better. So 
the Biogon has very even, very useable high performance.

The 21/4 C/V starts very good in the center, but not like the ASPH. 
It then drops so that by 1/2 oout is is noticeably poorer than the 
Biogon or ASPH. This is readily apparent on the M8.

So if you want tiny, you have to accept the slight falloff in 
performance in the C/V lens, which even at f/8 is not up to the 
others wide open. If money is plentiful, get the ASPH; it really does 
it all. If money is somewhat tighter, go for the Biogon f/4.5 for top 
performance, or possibly the Biogon f/2.8. Note: the f/4.5 Biogon 
extends only slightly further from the camera than the 3.4 SA, but 
the f/2.8 Biogon extends the furthest. The ASPH has a larger diameter 
than the Biogon, but it's shorter.

-- 
    *            Henning J. Wulff
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