Can anyone who has a Graphic Kowa lens factory mounted or professionally mounted in a Copal 1 shutter please measure the overall length of the lens cells in shutter? I'm interested in the spacing of both the 150 and 210mm focal lengths.

I bought both focal lengths in barrel, and while the cells screw directly into my Copal 1, I suspect something is amiss with the 150mm lens. When screwed all the way in to the shutter, my 150mm measures 38.15mm overall length. The resulting image covers 8x10, and while super sharp in the center, sharpness quickly degrades to mush 2-3 inches from the edges. When I unscrew the cells nearly all the way, to obtain 42.5 mm overall length in shutter, I get much improved sharpness over a smaller (about 260mm) image circle. My ultimate goal for this lens is to cover both 4x5 and 4x10.

While trial and error shows an improvement with increased spacing in the 150mm lens, I don't know the ideal distance I should be trying to achieve, and being off by several millimeters makes me queasy.

I've been very happy with the performance of my 210mm G-K on 8x10 at an overall length of 38.75mm fully screwed into the shutter, but I'd love to compare this distance with a professional or factory mounted specimen.

Thank you in advance to any who can contribute. These lenses are wonderful performers with absurdly large coverage for their diminutive size. But, as the annals of this forum attest, their specs are shrouded in mystery.