Strange issue with Preston and Zoom.
Hey guys, so I’m working on a show and we have a 150-600 zoom. Every once in a while when racking focus the zoom will also engage and go full tight without the operator’s involvement. We are using the digital microforce with the analog cable (so Preston motor for zoom). Anyone ever have any experience with this? Camera is Sony Venice.
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Could be a few things. Firstly the focus motor or focus gearing may be interfering with the zoom gear / motor and driving it through friction. Sometimes if the focus motor is pressed down onto the lens quite hard that can cause excess friction internally.
Second, the microforce could have a slight drift on the knob. Press set and reset on the DMF at the same time for three seconds. usually resolves drift
Third could be faulty board or cable on the DMF