Helicoid effect

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fferreres Veteran Member • Posts: 6,943
Helicoid effect

I was watching this video, and it became exactly as confusing as when I started trying to service the first lenses.

https://www.youtube.com/watch?v=yCsgoLc_fzI

See minute 13:27

One things move, and the thing moves in the opposite direction one would expect, and actually moves at a higher speed. I guess if you look at the video, you'll see what I mean. And that's very disconcerting at first about (dual) helicoids, because the twist of the barrel usually isn't turning at all, not the helicoid it's connected with, but the second indirect one, as the tab or guide locks them as in these two-medium example.

The author is offering some award (maybe is passed already?) for other counter intuitive things, and probably lenses and their mechanics have a lot, in case anyone wants to try  :-).

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