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Sven Schroder
14-Jul-2005, 10:17
Hi all

Having finally aquired a nice modern compur 0 for my 150/9 Germinar W (under the nose of the guy I bought the lens from no less) I phoned my dealer of choice to arrange for a correct aperture scale, " we'll have to get back to you on that" so I was waiting and remembered a post, in which Jim Galli discribed a method of transcribing apertures from barrel to shutter (with a spot meter and lightbox). Anyway the barrel and shutter scales match, the F5.6 scale on the shutter when stopped down to F8 matchs the F9 of the barrel and all aperture match even the half stops.
So my Question is do I need to get the new scale or stick with what i've got?

Ps Great lens and shutter combo and so lightweight.

Thanks Jim and Kerry and all on this forum.

Sven

Jeremy Moore
14-Jul-2005, 11:55
Some masking tape or computer labels to cover up the old numbers with the new and I think you are in business!

Emmanuel BIGLER
15-Jul-2005, 01:50
You just need to find the proper correspondence at full aperture. So if f/8 as engraved matches the full f/9 aperture of the Germinar, designing the new f-number scale simply means a shift by 1+1/3 f-stop ; f-9 = f-8 +1+1/3 f-stop. f-9.5 would be 1+1/2 f-stop.
You may also, just for fun, re-measure the actual diameter of the entrance pupil, which defines the actual f-number.
Place a small flaslight in the focal plane and illuminate the lens backward. place a piece of translucent paper against the entrance lens element and measure the diameter of the beam, this is the entrance pupil diameter. You should verify that @f/9, the diameter of the entrance pupil is 150/9 = 16.7 mm. @f/16 you should find about 9.3 mm. Alternativley you can also take a picture of the diaphragm with any camera fitted with a macro equipement and subsitute a ruler without changing the focus in the measuring camera to get the actual mesuremaent of the diameter.
To the best of my knowledge there are no clicks on the aperture ring of the copal --except on recent Schneiders-- , so you may place the figures of the new scale wherever suits you.