pfogle
04-20-2005, 13:03
I originally posted this on another thread, so apologies for the double posting, but I thought it might be of wider interest... the lens was focusing 8 inches in front at 6ft.
Here's the fix for the Avenon on my body... I used a fine (EE1 0) grit wet-and-dry on a mirror. Using a cheap dial caliper, I measured 0.98 mm at the start and 0.91 at the finish. In fact there was some variation around the rim, at the limit of what I could measure, maybe 0.02 mm. The attached pictures show how much the lens could screw into the adapter before I ground it and after. The angle of difference, 24 degrees, and the pitch, 0.75mm, gives a depth of 0.05 mm, which is pretty much what I originally calculated.
I think it's an under-correction, but since you can't put the metal back on, I decided to be conservative ;)
There's still a suggestion of front focus, hard to measure, but a definite improvement at infinity. As expected, the rangefinder now focuses past infinity, but only very slightly, and you'd never notice in practice.
All in all, it took about an hour.
One word of caution... be VERY careful not to get any metal dust in either your camera, or the focusing helicoid, which is very exposed on the Avenon. Please be careful here; I washed the adapter and dried it before each test.
Phil
Here's the fix for the Avenon on my body... I used a fine (EE1 0) grit wet-and-dry on a mirror. Using a cheap dial caliper, I measured 0.98 mm at the start and 0.91 at the finish. In fact there was some variation around the rim, at the limit of what I could measure, maybe 0.02 mm. The attached pictures show how much the lens could screw into the adapter before I ground it and after. The angle of difference, 24 degrees, and the pitch, 0.75mm, gives a depth of 0.05 mm, which is pretty much what I originally calculated.
I think it's an under-correction, but since you can't put the metal back on, I decided to be conservative ;)
There's still a suggestion of front focus, hard to measure, but a definite improvement at infinity. As expected, the rangefinder now focuses past infinity, but only very slightly, and you'd never notice in practice.
All in all, it took about an hour.
One word of caution... be VERY careful not to get any metal dust in either your camera, or the focusing helicoid, which is very exposed on the Avenon. Please be careful here; I washed the adapter and dried it before each test.
Phil