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RE: [OM] 90f2 with 80f4 CU lens (was OM2000 vs OM3)

Subject: RE: [OM] 90f2 with 80f4 CU lens (was OM2000 vs OM3)
From: Ross Waite <rmwaite@xxxxxxxxxxxxxx>
Date: Thu, 9 Sep 1999 08:55:55 +1000
On Thursday, September 09, 1999 3:51 AM, Tom Trottier [SMTP:tom@xxxxxx] 
wrote:
> Any difference in sharpness at different apertures?
> One advantage of the close-up lenses is much greater brightness, for
> shorter exposures & better viewing.


Nearly all of the shots taken with my 90/2.5 Tamron plus the Nikon 4T would 
have been at apertures of f8 or smaller.  I have not done any testing or 
comparisons with different apertures, but I expect that the 4T would result 
in some image degradation at wider apertures, but probably not as much as 
the simple one element CU lenses.

John Shaw describes the Nikon series thus: "When placed on a good lens, 
these dioptres are capable of first quality flat-field reproduction". 
(Outdoor Photographer November 1991.)  In his "Closeups in Nature" book, he 
also maintains that their quality also remains quite high when paired 
together.

After thinking more about this subject today, I realised that the 4T (52mm) 
may also work OK with the 90/2.  I will need to pick up a 55 to 52 step 
down ring first.  If it vignettes, I have only lost the few dollars cost of 
the step down ring.  If it works OK, I will not need to buy a 6T plus step 
up ring.

Cheers
Ross Waite




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