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Re: [OM] f-stops and t-stops

Subject: Re: [OM] f-stops and t-stops
From: Jim Brokaw <jbrokaw@xxxxxxxxxxx>
Date: Fri, 16 May 2003 14:36:27 -0700
I think the actual term is "T-stop". This derives from 'transmission' stop,
which is supposed to take into account all the internal light loss due to
actual physical factors like the number of elements, surface reflection
losses, mechanical factors like lens enlongation at close focus, etc.

I think most professional motion-picture lenses are marked in 't-stops', and
each lens may be a little different if they really do it right and measure
each individual lens.
-- 

Jim Brokaw
OM-'s of all sorts, and no OM-oney...


on 5/15/03 2:45 PM, petertje@xxxxxxxxxxxxx at petertje@xxxxxxxxxxxxx wrote:

> 
> Hi,
> 
>> Date: Thu, 15 May 2003 01:21:21 -0700
>> From: Moose <olymoose@xxxxxxxxxxxxx>
>> Subject: Re: [OM] f-stops and p-stops
>> 
>> OK, the 'f'' f-stop stands for 'focal ratio' and the 't' in t-stop for
>> 'transmission', i.e. the actual light that comes through. Where does
>> 'p-stop' come from? A mishearing of 't-stop', or some other even more
>> esoteric meaning. Not arguing with your tests, just wondering about the
>> nomenclature.
> 
> The "p" stands for
> "Perhaps-I-should-try-a-random-letter-because-I-forgot-what-the-real-term-was"
> :-)
> 
> Can anybody quickly rename all my previous posts and save me from losing face
> in front of future generations ?
> 
> 
> Peter.


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