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Re: [OM] filters, again.

Subject: Re: [OM] filters, again.
From: John Robison <omrobison@xxxxxxxxx>
Date: Fri, 5 Nov 1999 06:42:50 -0800 (PST)
  In conection with this thread; in the late 70's I
sold a Vivitar 400mm lens and Vivitar UVa filter to
one of our regular customers. He developed and printed
his own B&W, and the the lens just would not reach
inifity. All long distance shots were not as sharp as
closer pictures. We thought the lens was at fault, but
it turned out that without that filter the lens
performed fine. We tried a different Vivitar UVa
filter and the second filter presented no problems.
Kinda makes you think. 

--- PCACala@xxxxxxx wrote:
> Dirk writes:
> 
> < Can you test some Tiffen filters? I can send you
> some if you need them. >
> 
> Well, I'm not in a position to impose on a repair
> shop.  Why not take all 
> your filters to a shop that does lens work and see
> if they can test them?  It 
> just a typical star test like used for lens
> centering.  If the star rotates 
> when you rotate the lens, or the star has multiple
> images, then you have a 
> less than perfect mount and/or glass.
> 
> I shot my test map with a "bad" Vivitar ND 0.3
> filter. I had a Hoya which was 
> equally bad, too. I used my finest performing 50mm
> f/1.4 Zuiko, with shots at 
> all apertures.  I'll side by side compare them to
> shots without the filter 
> and will have results significant at the 1/3 grade
> level (A- vs. A, for 
> example).  Maybe it'll be a wash, who knows.  The
> slides come back on Friday.
> 
> Keep this in mind: production variations might be
> more important than brand 
> names.  I picked up on Bill Roger's interest because
> everyone knows I'm 
> anti-marketing ("brand bah hum bug") and the
> scientist in me likes to 
> question dogma ("this filter is better than that
> brand of filter").  What 
> Bill has learned is that sticking to a particular
> brand of filter insures 
> nothing with respect to flatness and plane
> parallelism.
> 
> I can just hear some folks saying: "Oh, gosh, I
> thought my worries were over 
> when Gary tested the kind of lens I own.  Now I have
> to worry about my 
> filters, too."  Sorry folks . . .
> 
> Gary Reese
> Las Vegas, NV
> 
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> 


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