[LargeFormat] An 11x14 Ektachrome shot with rear half of a Protar VII convertible

[Richard Knoppow]

----- Original Message ----- 
From: "Jim Hemenway" <Jim@hemenway.com>
To: "Large Format Group" <largeformat@f32.net>
Sent: Monday, October 13, 2003 12:49 AM
Subject: [LargeFormat] An 11x14 Ektachrome shot with rear
half of a Protar VII convertible


> http://www.hemenway.com/CharlesRiverProtar590.jpg
>
> The Boston skyline from the MIT boat house.
>
> I've added the following info as there were some questions
recently
> about aperture scales and individual cells for the Series
VII.
>
> This photo was taken with the rear cell of a B&L Protar
VII.  Both front
> and rear cells are the same... 23 1/4 inches - f12.5 when
used singly,
> (about 590.55mm), and 13 1/4 - f6.3 when used together.
>
> The unit has two aperture scales, the outer for both cells
at f6.3 and
> the inner for a single cell at f12.5.  It's mounted in a
Compound shutter.
>
> The front cell has a serial number ending with 7344.  The
engraving on
> the rear cell has a lot of wear but appears to end in
7343.
>
>
> Jim - http://www.hemenway.com
>
>
   This is a quite remarkable picture. I suspect that with a
strong loupe you can peek in on some of the secretaries
adjusting their garters.
   My Convertible Protar does not seem to have any color
fringing. Fringing would certainly be obvious in yours
because of the much longer focal length.
  Note that the effective speed of a single cell depends on
which side of the stop its mounted. In the normal position,
behind the stop, the physical stop is the entrance pupil and
the speed is f/12.5. If its mounted in front of the stop
there is some magnification of the stop so the speed is
increased a little, maybe to f/11.5 Behind the stop is
optimum for best correction but the shorter bellows draw
when its in front is sometimes more important.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com