Jedy Posted June 4, 2017 Share Posted June 4, 2017 I have a 5DmkIII and Canon 24-105mmL and 70-200L, both f4. I purchased a good quality follow focus earlier this year (from shoot35.com). The issue I'm experiencing is the dreaded lens wobble when engaging the follow focus (the lens physically moves). I assume it's caused by the follow focus torque as moving the focus ring by hand doesn't cause this problem. I am currently using a cheap gear ring belt on the lenses. As the photo below shows, the drive gear is very small. The company offer bigger drive gears at additional cost. I am hesitant right now in simply buying anything on the slim off chance it solves the problem as I have wasted money in the past this way. Of course I'd spend money if I knew it would help solve the problem. I am looking to invest in an external monitor/recorder (Atomos) this year as investing in a proper film camera is out of my reach right now and this issue pretty much makes my rig unusable. Any help/advice would be greatfully received. Quote Link to comment Share on other sites More sharing options...
gsenroc Posted June 4, 2017 Share Posted June 4, 2017 I had this issue as well. You need a lens support to hold it in its place. Quote Link to comment Share on other sites More sharing options...
Jedy Posted June 4, 2017 Author Share Posted June 4, 2017 Unfortunately the lens support I have isn't very effective, plus it gets in the way of the mattebox. Quote Link to comment Share on other sites More sharing options...
no_connection Posted June 4, 2017 Share Posted June 4, 2017 Is it while focusing or does it "move" the lens when you put it on? You could add another wheel to the other side to counteract some of the static side forces. If it is wobbling while turning then adding a linked wheel to the opposite side that turns as well should do the trick as it would cancel the up/down force added to lens. No idea if that exists tho. Another idea is a big ball bearing and a short "pipe" through it, The follow focus makes contact with the outside of it but not the lens. The lens is then couples at all sided to the inner part of the very short pipe. That way the pipe takes all other force and only transfers rotation to the lens. This would also support the lens as well. How much depends how soft the linking material is. The outside of the ball bearing would be securely fastened to the rails. Last idea (and maybe the simplest to test) would be adding a timing belt and use that to contact the lens. And not having the gear make the connection. Then add a small freerunning wheel to counteract the timing belts force (that would not be much). This however would reverse the direction, but the follow focus might have and option for that. *edit* Oh last last idea, add a belt that is freerunning but there to counteract the force of the follow focus. Essentially pulling the lens towards the wheel instead of it pushing against the lens own "bearing". It could use the same area or even a timing belt but have a wheel just beyond the driving wheel. Actually thinking about it. If you have another wheel the same size as the driving wheel, if you link that and have a timing belt that wraps around the lens, you would both get drive, solve the static load problem, and add some better grip while your at it. I can draw up a diagram if you want. Quote Link to comment Share on other sites More sharing options...
Jedy Posted June 4, 2017 Author Share Posted June 4, 2017 The lens only moves whilst focusing. I believe the torque from the follow focus (it has to be fairly tight to remove any play in the follow focus) is pushing against the lens causing it to move. The cheap gear ring belt may not be helping either for all I know but I don't want to invest in a pricier lens gear solution if it turns out not to help. Thanks for all the suggestions. I'm aware dslr's were never originally intended for video work and in many ways are not ideal. I am going to borrow another lens support which should fit my rig better than mine and will see if it helps. Quote Link to comment Share on other sites More sharing options...
no_connection Posted June 4, 2017 Share Posted June 4, 2017 Can you post a picture of your exact rig from a few angles? Quote Link to comment Share on other sites More sharing options...
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