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[OM] Re: Why is there no 60mm lens ? Was: 7519772104 reasonable 40f2

Subject: [OM] Re: Why is there no 60mm lens ? Was: 7519772104 reasonable 40f2
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Fri, 03 Jun 2005 10:37:59 -0400
I have always wondered about this myself.  It wasn't long after I bought 
my first SLR many years ago that I realized that the lens lines tended 
to be separated by the square root of two such that stepping from, say, 
24 to 35 to 50 would cut the area encompassed by the picture in half 
with each step.  But, where one would expect to find a 70mm lens, there 
was a hole until you got to 85mm, then a bit of confusion between 85 and 
105 where one would simply expect 100mm.  Then the sequence resumes 
again (roughly) with 135 (140) and 200.  Then it should go to 280 and 
400 but 300 is much more common than 280.

I've never understood this.  Does anybody?  Maybe the 85mm lens is 
supposed to be double the 43mm that almost no one made.

Chuck Norcutt

Der Eiserne Reiter wrote:

> The one thing I have always been wondering:
> why has 60mm not been a popular focal length ?
> 
> To explain: I think about focal length in terms of area mapped to film.
> When I take a lens set on a walk, I try to pick a combination where each
> lens gives me factor 2 (or half) of the image compared to the next lens in
> the line-up (speaking digitally, when scanned, I get twice or half the
> resolution). For this to work, the focal lengths should have factor
> 1.4 as multiplier (1 "stop"). So, for instance,
> 
> 17, 24, 35, 50, 75, 105
> 
> is a great line-up in these terms. Or
> 
> 15, 21, 28, 40, 60, 85/90, 135
> 
> fit very well, too. (I do not mean to imply that I own all of these Zuikos 
> ...)
> All these lengths are very popular, except for 60mm.
> Does anybody know why almost no 60mm lenses were built in the past ? There are
> a few 55s (one Zuiko), a 65 Elmar, and the 100mm Zeiss/Hasselblad (which 
> corresponds
> to 60mm). There is a 60mm half-frame Zuiko, but this corresponds to a 
> different
> length in full-frame.
> 
> Regards,
> 
> Roland.
> 
> 
> 
>               
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