Why have helical focusers become popular? (1 Viewer)

[Humboldt]

According to a Zeiss representative I spoke to recently, helical focus is a more robust and durable design. Double-focus, as on Kowa for example, consists of more smaller parts and rubber straps and is generally a more vulnerable construction. Whether this is sales talk or not I can't say, but if you look at exploded views of the Kowa you can see that it's small wheels and belts that do the focusing.