[LargeFormat] Trouble with calculating F-stop

[Les Newcomer]

First off, the non-dotted Artar was designed for the Graphic arts industry.
   it's home was usually in the back of the graphic arts house on the front 
of a 24x36 galley camera  with some arc lights nearby and a dozen men in 
white shirts smoking camel cigarettes talking about the new Tucker or 
Turnpike Cruiser, depending on the decade.  It was hot in the summer and 
drafty in the winter and smoky all the time.

The filter drawer is for waterhouse stops.  I'm not a Graphic arts expert,
  but they've been experiementing with different shaped holes for years.  I'
ve got kodak catalogs from the teens showing square stops for "graphic 
purposes"
Any more questions? ask away.  As Gregory Peck said at a Q&A session with 
some film students, "you ask the questions you want, and I'll give the 
answers I want."


On Sunday, October 27, 2002, at 08:54 PM, Guy Glorieux wrote:

> Thanks for both your replies, Les.
>
> I'm just a bit perplexed by your comment on the Atar being symetrical
> and the implications for the focal length and the aperture.
> I will come back to you on this since I'm really squeezed for time the
> next three days.  But there are features of the Atar that I did not
> expect to find when I bought it this past spring which you may be aware
> of (e.g. the opening on the side for waterhouse stops, as it seems).
>
> Thanks again and I'll be back around the middle of the week.
>
> Guy
>
>
> ----- Original Message -----
> From: "Les Newcomer" <lnphoto@twmi.rr.com>
> To: <largeformat@f32.net>
> Sent: Sunday, October 27, 2002 10:37 AM
> Subject: Re: [LargeFormat] Trouble with calculating F-stop
>
>
>>
>> On Sunday, October 27, 2002, at 07:21 AM, Les Newcomer wrote:
>>
>>>
>>>> Greetings colleagues,
>>>>
>>>> I've been away for a while from the list but I'm back now and
> apologize
>>>> for cutting into an interesting discussion on photography as art.
>>>>
>>>> I'm running into a frustrating problem with determining the actual
>>>> F-stop aperture on  the lenses for my 11x14 camera.
>>>>
>>>> One lens is an old Wollensack 18.5" triple convertible, with the
> F-stop
>>>> running from F 4.0 to F-256 at the 18.5" focal.  However, when I
> try to
>>>> use the indicated F-stop with my meter, I get an image that is way
>>>> over-exposed.  In fact, if I calculate the diameter of the aperture
> at
>>>> 18.5" focal at, say F-128, it gives me F-45 instead of F-128.
>>
>>>> I have exactly the same problem with another lens, an 19"
> apochromat
>>>> Atar F11.
>> Now it's a different problem with the Artar since at f11 it can't be
> in US
>> stops (US doens't have a US11)
>> I'm not sure what to tell you on this one.  Is it all there?  Since
> the
>> Artar is symetrical, you can use half of it. This gains you a 1.75x
> focal
>> increase and a decrease of about 2 stops.  there should be cells
> (glass)
>> both front and back.
>>
>> Les
>>>>
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>>>>
>>>
>>>
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