Sounds great. You should definitely make a video, or take some photos of it.

Ultimately i'd like to get hard stops sort of working, and my main motivation was to try and get something that's going to be as gentle as possible on the lens itself, I don't want to strip the rubber of the ring, or scratch a metal focus ring.

Another nice benefit of this particular jar opener is that the rubber and handle dampens your focus action, i tried to show a closeup of this action at the end, but it feels like you can get a very nice smooth start and finish to your move by letting the rubber absorb some of the motion. To be honest I tried this jar opener on a picked beetroot jar earlier today and found it didn't work very well at all, that same dampening and give that works a charm for this application makes it a pretty lousy jar opener. :)

How do you stop your zip ties from freely rotating on the lens? Have you tried it on an all metal lens? A tip if this ever becomes a problem is to put some elastic bands on first, and then tie your zip tie or whatever over the top. The rubber friction will stop any slip, which lets face it would be catastrophic if it caused your focus marks to be shifted.

I put the zip ties on the rubber focus ring of the lens, with the teeth of the zip ties facing inward so they can "bite" into the rubber. If you pull on it to hard, you can get it to slip. I don't want it on their to tight, as I want to slide it on and off the lens. It has the same dampening effect as your jar opener as I left each end long. The added advantage is, I can mark focus points on it with the erasable marker-that was the most important thing to me.
You will find that with dampening, the focus is not as precise. And, when your shooting an F2.0 lens, you really need to be extremely precise with your focus pulls, as the DOF is razor thin.

Also, the GH1 only does magnification in manual focus mode, while it's not recording. So you need to lock everything down, do your focus pulls, and mark everything-then go back and triple check your focus "dots", just to make sure you got it exact, before you start recording.
You're just not going to be able to accurately pull focus while recording, even with a follow-focus unit, just by sight alone. You need reference marks, and that magnified screen.

I use this on my Nikon 50mm F2.0. I don't use it on the Panny lenses, because they are "focus by wire", and your reference "dots" may move when you start shooting, depending on how fast you roll into focus. So that's kinda a waste of time.

I edited the topic title to just DIY follow focus, seeing as we're discussing lots of different types.

@havasuvideo nice idea having the zip ties on backwards, a nice solution to the gripping problem, though it'll only work ok on rubber focus barrels i guess. I think an elastic band or similar would offer you grip on those though with the zip ties on either way round.

I'll be trying to use my concoction in earnest this coming weekend so will see how it works out, I'll be using it on the Nokton 25mm f0.95 so I know what you mean about narrow DOF. And already by eye i've noticed that the damping makes it interesting trying to come to a stop on the mark, will see.

My reference marks are the markers stuck onto the velcro disk that the match stick lines up with. They can be placed easily and i've numbered them to have a sequence of focus points easy to move between. Will see how it stands up in use.

I'll see if that damping does become and issue in practice, it doesn't feel like it should do with quick testing, but when you're actually trying to nail a focus pull it may be a different story. It's first trial by fire will be this coming weekend.

Cheers

@jimtreats.....I came across a method were you can use a rubber band with a cheep tripod that allows you to get smooth panning.

If you shoot with MF lenses, as I do all the time, you'd notice many of these lenses have very short throws. Defeats the purpose of putting the additional weight on the rig, when pulling focus on the lens itself is so much faster

I had to part in 2 (the long way) my jar opener for it not to rub the focus ring of my 14-140mm, 20mm pana, 14mm pana and 50mm smc takumar and it works !! See there for the marks on the lcd screen : http://www.personal-view.com/talks/discussion/5111/gh2-14-140mm-focusing-points-in-advance...

Diy FOLLOW FOCUS by changing the direction of rotation. Most elements are by hard disks,main bearing. I think it's a good idea for a variety of lenses -left or right focus