Follow focus drive gear size

[Doug_EX]

Hi,

Was wondering what is a good size drive gear for a lens with a short throw...like photo lenses.

Thanks!

 

[Bern Caughey]

Not sure this helps but ARRI uses a 1:1 gear ratio for dSLR lenses.

"Cine has a gear ratio of 2:1 for cine style lenses
The MFF-2 Cine has a gear ratio of 2:1, which means one turn of the focus knob will result in two turns of the focus gear. This gear ratio is common to all classic follow focus units from ARRI (FF-3, FF-4, etc.) and is traditionally suited to cine lenses such as Ultra Primes, Compact Primes, Alura Zooms, Angenieux Zzooms, etc...

HD has a gear ratio of 1:1 for 2/3” broadcast and still photo lenses
The MFF-2 HD has a slower gear ratio of 1:1. In this case, one turn of the focus knob will result in a single turn of the focus gear. This particular gear ratio might be preferred when using lenses with a short focus throw, where the scale from minimal focus to infinity is so short that a traditional 2:1 ratio could be too direct, lacking in precision. Typical lenses suited to the HD ratio are modern still prime lenses, some ENG zooms, extreme wide-angle lenses or some older designs."

http://www.arri.com/camera/pro_camera_accessories/learn/faq_follow_focus/

 

[Doug_EX]

Thanks for the link. It helped me quite a bit.

 

[Doug_EX]

I thought that a ratio of 1:1 was for cine lenses. Thank you!