Archived posting to the Leica Users Group, 2010/11/07

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Subject: [Leica] 90 AA - focus shift?
From: benedenia at gmail.com (Marty Deveney)
Date: Mon, 8 Nov 2010 11:17:01 +1030
References: <C49D8150-E2D0-4E99-91F7-F8707FA3E566@125px.com> <89693D1F-AE98-44D0-8895-EE67BDE15556@shaw.ca>

There is a loss of performance close up even when you correct for
focus shift; the absence of a floating element is telling.  Resolution
drops but more importantly contrast decreases.  Either the 75
Summicron or the Zeiss 100/2 Macro are much sharper inside 2 m (I have
tested them) as should be any well made lens with a floating element
(I just haven't critically tested any others against the 90 AA).

Part of the problem is that the performance is so good at longer
imaging distances.  The contrast of the 90 AA is too high for my taste
but if you like that it's an amazing lens.

Marty

On Mon, Nov 8, 2010 at 9:54 AM, John Collier <jbcollier at shaw.ca> wrote:
> I can't comment on the digital/focus shift issue but my 90/2AA was tack 
> sharp though out the focus range. Wide open it was slightly softer in the 
> corners up close but only slightly and light years ahead of any other 80 
> to 110 lens.
>
> John
>
> On 2010-11-07, at 1:20 PM, Tim Gray wrote:
>
>> I've heard the 90 AA is a wonderful lens. I've also heard that it is 
>> horrible below 3 m OR it loses a bit of performance in that range. 
>> ?Probably closer to the latter, but I'd like to hear opinions on that if 
>> you have any. ?How good/bad is it closer in?
>>
>> Which brings me to my 2nd question. I've read that the decrease in 
>> performance close in on this lens is due to focus shift. True? Does that 
>> mean there is a plane of bitingly sharp detail, but just not where you 
>> want it to be?
>
>
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In reply to: Message from tgray at 125px.com (Tim Gray) ([Leica] 90 AA - focus shift?)
Message from jbcollier at shaw.ca (John Collier) ([Leica] 90 AA - focus shift?)