I started out this project intending to only buy and adapt ONE lens, the P6x7 75mm to the Speed Graphic.
Well by now I have 3 P6x7 lenses. The 4th addition to the 6X7 collection is not a Pentax lens.
It is a Computar f/16 105 ~ 150mm Variable Focal lens from Surplus Shed.
It can only be used on a camera like the Speed which has a front rack.
I took the lens apart for cleaning. There is a fixed f/16 stop inside which can be removed to make this lens f/5 or so, but I decided f/16 is a good general aperture. (Although it is a very bright day in Michigan today and down to f/22 and 1/1000th on the ME super in early afternoon).
Some search reveals that this lens was used in Camerz cameras which were 70mm long roll cameras, electrically powered, which were used to photograph the school kids in USA from 50's until digital days.
So the lens is ideal for 6 by 7, 6 by 9 etc. It came with a nice metal hood and shares a 67mm thread with the P6x7 90 mm LS.
I made a lens board, and non destructively added a stainless scale rule to the rack. Then tabulated infinity, 20 meter, and 5 metre for 105mm, 135 mm and 150 mm.
Focus is not critical at f/16, and I hope to mostly just use tabulations and not need the ground glass. The Speed is set up with cam and scale for 135mm, and the viewfinder is almost covering 105 mm at its edges.
Making the Computar lens board
https://www.box.com/s/l0abmpqgjot97xjnp4af https://www.box.com/s/gxfofae5bu7mhmgupt97