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Re: [OM] Speed of lenses

Subject: Re: [OM] Speed of lenses
From: "John A. Lind" <jlind@xxxxxxxxxxx>
Date: Mon, 09 Oct 2000 20:42:30 +0000
IMHO it's a combination of the two.  Aberration at the edge is a real
design problem.  To make a lens faster, the elements themselves can become
more complex, including the need to add an additional one and changing the
designs of existing ones.  Example:  to get the CZ Sonnar from f/2 to
f/1.5, Ludwig Bertele had to go from 6 elements in 3 groups to 7 elements
in 3 groups.  The f/2.8 with in-lens shutter version has 5 elements in 4
groups.  If you look at the cross-sections they are all very similar
meaning they used the same basic design with tweaks on the faster ones for
speed, including more elements for correction.

More OM related are the 50/1.8, 50/1.4 and 50/1.2 lenses.  The f/1.8 has
six elements, and given the reputation for the sharpness of the MC version,
it is simpler because it can be simpler as a slower lens.  The f/1.2 and
f/1.4 look very similar.  All appear to be symmetrical in basic design,
meaning they should be very well corrected.  The higher cost is also demand
and production related.  It is more difficult to make big pieces of glass
into large high precision lenses than it is for smaller ones.

Last, there's also "what the market will bear."  Certainly no "for profit"
company is going to sell a lens at a loss, but that doesn't mean there's
necessarily a tight relationship between cost of design and manufacture,
and its retail pricing.  If the market will bear a higher profit margin, it
will be sold at the higher profit margin.

-- John

At 15:57 10/9/00 , Giles wrote:
>
>I don't think they are obligatory, though they are often used for longish 
>telephotos to maximise the performance.
>
>I think what happens, at least with Zuikos anyway, is that Olympus says - 
>well this faster version is going to cost more due to the larger size so 
>we might as well go to town on it and make it as well as we know how to.
>
>This would possibly explain why the faster Zuiko lenses are that much more 
>expensive and why they usually have better performance.
>
>Giles
>
>
> Gregg Iverson wrote:
>
>> Does a faster lens usually also require more exotic materials or 
>> engineering the way a faster car seems to?


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