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Getting more throw on Follow Focus?


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#1 Landon D. Parks

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Posted 05 November 2018 - 07:17 PM

I currently have the JTZ follow focus system, which provides a fine throw on my Rokinon CineDS lenses... However, when I use my smaller handheld setup with my Sigma 17-50 lens, the focus ring on the lens is only about 45 degrees, which results in a terrible throw for the focus wheel.

 

I was looking into some of the JTZ extension arms that provide different throws, for example, there are 1:1, 1:1.5, and 1:2, but the idea of what they do is seeming to fly over my head. If I attach a 1:2 extension arm to my follow focus, does that mean the throw will be 2x what it was prior, essentially making the 17-50 a 90 degree throw instead of 45?

 

Thanks! 


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#2 Bob Speziale

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Posted 05 November 2018 - 10:11 PM

I haven't used it but it seems like it should. Think of turning a bicycle wheel by pushing your finger against the spoke. Pushing the spoke near the hub of the wheel requires just a few inches of finger movement to rotate the wheel one revolution. Placing your finger farthest away from the hub nearest the tire, you would have to push the spoke several feet to get one revolution.


Edited by Bob Speziale, 05 November 2018 - 10:14 PM.

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#3 Dom Jaeger

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Posted 06 November 2018 - 02:53 AM

 I was looking into some of the JTZ extension arms that provide different throws, for example, there are 1:1, 1:1.5, and 1:2, but the idea of what they do is seeming to fly over my head. If I attach a 1:2 extension arm to my follow focus, does that mean the throw will be 2x what it was prior, essentially making the 17-50 a 90 degree throw instead of 45?


I would assume that it expands the throw yes, but maybe double-check by asking the manufacturer or sellers. You can also use different sized gears at the lens interface to achieve a longer throw, a gear with more teeth (but still the same mod 0.8 pitch) will also expand the throw. I'm not sure what this brand offers in terms of lens gears.
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#4 Dom Jaeger

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Posted 06 November 2018 - 06:16 PM

Sorry, I should correct myself - a gear with LESS teeth will expand the throw, that is to say turn the lens focus ring more slowly.
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