Archived posting to the Leica Users Group, 1998/12/09

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Subject: Re: [Leica] APO 2X extenders - non ROM?
Date: Wed, 09 Dec 1998 22:59:02


 I read a little about the 2X non-APO Extender in Leica R Compendium.
There it says the non-APO Extender is not supposed to be used on APO prime
lenses like 100 APO.  It also mentioned that APO 2X Extender was designed
to compensate the image quality loss in the non-APO Extender.  What gives?
 What is the advantage of the APO Extender compared with the non-APO
Extender?  I know the price is almost double.

Best Wishes,

At 07:32 AM 11/30/98 -0800, you wrote:
>David Young wrote:
>> What would be the difference in quality between APO 2X Extender and plain
>>2X Extender?  How much does the non-APO Extender degrade the quality when
>>used with one of the prime lenses?  Reduction of largest aperture by two
>>stops sounds inconvenient to me.>>>>>>>>
>Hi David,
>There isn't any glass quality difference between apo 2X and 2X ROM. The
>only difference is the ROM connection. And as far as the 2X APO and the
>older non APO I've not seen any great heart thumping difference.
>There isn't any degradation that is possible to see with the normal eye and
>I doubt any on a test bench. The loss of 2stops is insignificant unless
>you're working in absolute minimum light to start off with.
>I've used the 2X since it arrived on the market on the 15mm to the 400 2,8.
>The only time you can pick-up any minimal softening is when you stack the
>extenders to-gether on the same lens.
>If you use the 1.4 on the apo 280 2.8 it becomes a 400 f4;  then add the 2X
>and it becomes a hand holdable 800mm f 8.0.  It works wonders, with very
>slight softening at the corners if used wide open. A one stop down and it
>works fine.
>Ted Grant
>This is Our Work. The Legacy of Sir William Osler.