So I'm on a job at the moment using a set of Master Primes on the RED.
I have an MK-V FMG 6 and a BFD.
Our widest Master prime is an 18mm, and we have Super Speeds which are wider. Today we had the 18mm on the camera; I was calibrating the BFD on the lens. I started to roll out the wheel, and the motor and the lens started to violently twitch. I initially thought it wasn't getting enough power, but all I had to do to stop it twitching was apply a bit of pressure to the focus ring. Once that was done, the twitching stopped temporarily, that is until you made any move on the lens again, where it would commence rapidly twitching.
We took the motor off the mount on the bars, held it against the lens, and tried to calibrate again, no issues at all. It was just when back on the bars that it started twitching again. We tried mounting the motor at various different angles and the same would happen. We also tried to vary the amount of contact pressure against the lens with the motor.
Eventually after a bit of swearing and some head scratching, we swapped the 18mm for the 12mm Super speed, and everything worked perfectly.
There was a bit more resistance from the Super Speed, a tad stiffer.
The Master Primes are silky smooth and very easy to turn.
As I say, the only way I could stop it from twitching was to apply some pressure to the focus ring as the motor was engaged and doing its thing.
It couldn’t have been a signal interference issue as it worked fine with the Super Speed, also when in calibration mode and with the transmitter off, it would be irrelevant.
I checked that everything was tight on the bars, no movement there at all.
With the motor off the lens rolling out the wheels, the motor was fine, nice and smooth.
I’m stumped on this one, and any insight would be appreciated, especially as I’m back on it in a few hours.
Edited by Richard J Lewis, 28 September 2008 - 06:26 PM.