What the thread found

• A functional follow focus system can be constructed for under $400 using a digital proportional radio transmitter, receiver, servo motor, and mounting bracket.
• Standard RC servos have limited rotation ranges, typically 120 degrees or less, which restricts their ability to control focus across the full range of some camera lenses.
• Larger gear ratios compensate for limited servo rotation but reduce precision and force delivery at the gear teeth.
• RC servos operate as open-loop systems without feedback, unlike professional motor systems that use closed-loop control for improved accuracy.
• Modifying RC servos by adjusting internal potentiometer resistors can extend their rotation range beyond the standard 120 degrees, though excessive modification can cause continuous motion.
• Multi-turn motors with 5-7 turn capability provide better control range and power than standard RC servos but require different receiver compatibility.
• RC servo-based follow focus systems work adequately for video lenses and low-budget productions but show precision limitations with stiff 35mm cinema lenses.
• RC servos generate audible mechanical noise during operation.
• A DIY system serves well as a backup to rented professional follow focus equipment.

Depends on

• The technology discussion spans from 2007, with servo specifications and available products likely changed significantly since then.
• The rotation modification technique described is experimental and requires careful tuning to avoid causing malfunction.
• Performance varies greatly depending on lens type and focus range requirements.
• Compatibility between RC receivers and professional multi-turn motors was not conclusively resolved in the discussion.
• One participant claimed modifications to extend servo rotation work well with video lenses up to 25mm but encounter problems with 50mm lenses.
• The claim about Heden motor internals containing a Faulhaber motor is mentioned but not independently verified in the thread.

Parts

Follow Focus

Same gear or parts

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