Hello,
Although the focusing on my Tachihara Hope is smooth when the lens is little extended, it grows tighter as it moves out, growing uncomfortably tight by the time I reach the area I’ll be using most, about 8 1/2 to 10 inches of extension (with my 210). By uncomfortably tight, I mean that the I can turn the knurl but the movement is quite stiff and causes just enough jitter — because of the friction, it jumps a bit rather than moving continuously — to make fine focusing difficult as the image on the ground glass jiggles. It’s not clear to me where the friction would tend to be and, therefore, what to try to do about it. There’s probably an ordered series of things to try.
For more details: 2d animation
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