[Leica] LHSA convention cluster bombs Part One The Beginning.

[henningw at archiphoto.com (Henning Wulff)]

At 8:06 AM -0500 11/3/04, Dan C wrote:
>I've missed something here.   I can understand why someone might not like
>the ASPH correction in a lens;  I *think* it is residual spherical
>aberation which is the basis for lovely "bokeh" which people get soft and
>fuzzy over (or conversely might be the cause of "brittleness"), and which
>is highly corrected in aspherical designs.    APO design merely reduces
>chromatic aberation, which I can't see having an unintended detrimental
>effect on a len's performance.
>
>-dan c.
>
>  At 07:48 AM 03-11-04 -0500, William G. Lamb, III wrote:
>>
>[snip]
>>
>>So let's not get too wound up here, O.K.? I would LOVE to fill that 75mm
>>frame on two of my M's. If it's an ASPH, that could be very good. If it's
>>got APO correction, I'll be more inclined to wait and see some results
>  >before springing for one. That's all...

That was exactly where I was heading, but I never got a response to 
my question about what the problems was with 'APO'. APO correction 
helps lenses, particularly longer lenses in a number of ways, but has 
no influence on 'brittleness', which I assume is a description of 
harsh bokeh. 'Good' bokeh relies on staying on the side of 
undercorrected spherical aberrations, rather than fully correcting, 
or, in the worst case, overcorrecting.

I find the 90AA to be extremely well corrected, but not 
overcorrected. Compared to the older 90 Summicron, it does not have 
as smooth bokeh, but the older lens unfortunately also has smooth 
'bokeh' in the areas that should be sharp, which can never be said 
about the 90AA.

I find the performance in all regards of the 90AA very much in line 
with the other ASPH lenses I have.

-- 
    *            Henning J. Wulff
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