[LargeFormat] Trouble with calculating F-stop
Les Newcomer
largeformat@f32.net
Sun Oct 27 10:40:06 2002
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
>>
>> _______________________________________________
>> LargeFormat mailing list
>> LargeFormat@f32.net
>> http://www.pairlist.net/mailman/listinfo/largeformat
>>
>
>
> _______________________________________________
> LargeFormat mailing list
> LargeFormat@f32.net
> http://www.pairlist.net/mailman/listinfo/largeformat
>