What's so hard about a DIY Follow Focus?

[Charles Papert]

So my question is this: how often do you guys use focus pullers on your DV shoots? If so, do they use tape measures, or do you do the zoom-in/focus/zoom-out method to give them marks? How often do you do severe rack-focuses? Couldn't they just pull off the lens barrel?

Or is the goal to dress the camera up so it looks fancier?

[Michal Spimr]

btw jbk sells follow focus for 750..lol so I guess that is like half the price what Chroziel is charging. we're getting closer..lol

[Oscar Spierenburg]

One thing about Sarena Valilis reply. That reaction goes for almost all posts on a 'Alternative Imaging Methods'
But that's what this board is about. When I'm fixing my old-timer car, of course it takes me 10 times as much time than a professional mechanic and maybe it'll fall apart in a week, but it's a lot of fun to make something yourself and it cost you nothing, most of the times.

Shannon, A Body Mounted SteadyCam? I don't know about that. If you put two tripod heads on top of each other, one facing sidewards, you have the most difficult part already.

Have people thought about parts of old sewing machines to use for a follow focus?

[Joshua Starnes]

<<<-- Originally posted by Charles Papert : So my question is this: how often do you guys use focus pullers on your DV shoots? If so, do they use tape measures, or do you do the zoom-in/focus/zoom-out method to give them marks? How often do you do severe rack-focuses? Couldn't they just pull off the lens barrel?

Or is the goal to dress the camera up so it looks fancier? -->>>

For straight DV shoots with the regular lens, I wouldn't bother. On some of the things I have shot, it would be easier to have a second person doing the focus, but most of the time it's not.

On the other hand, when dressing the camera up with cine lenses, I go the full monty - it's just easier to have someone else doing the focus themselves and it's easier for them to do it with an FF. We do bring the tape measure - sometimes it gets used, sometimes it doesn't. Of course, I also always bring my light meter even when I shoot DV, so maybe I'm just weird.

[Richard Mellor]

I use this on a homemade 35mm adapter, with a canon 1.8 lens.
It fits right in with the under $200 total cost .

shallow depth of field on minidv for less than $200.




http://www.tabletools.com/tabletools...strongboy.html

[Dan Diaconu]

I leave it with you:

http://www.jbkcinequipt.com/ffSkech.jpg

free, just make it.

[Oscar Spierenburg]

There are screwdrivers that have a 90° twist. The mechanism is very precise. This should easily be converted in a follow focus similar to Dan's.

[Aaron Shaw]

Dan did you draw that?

Oscar: Interesting idea! I'm not sure how much it would help though. It would certainly allow you to adjust the focus manually but I'm going to want to use a focus puller (either attached by wire or wireless) farther away from the camera (moving shots etc).

[Charles Papert]

Wireless lens controls is a whole other ball of wax from a mechanical follow focus. There have been a few systems built from RC technology, one of them even became the industry standard for Steadicam back in the 80's. However the degree of precision required to adequately follow focus with repeatable marks is pretty sophisticated engineering. As we all know, RF is prone to interference (the higher-end wireless focus systems use microwave) and the data stream is pretty high to ensure good response. It's one of those things that if it were mass-produced, it could be made fairly cheaply, but it isn't, so it isn't.

Here's a clip of my wireless lens control system in action that our own Chris Hurd shot when he was visiting me on set while in town for a trade show.

[Aaron Shaw]

Oh indeed! That's why I'm thinking about going the "tethered via a wire" route. Infrared could also be used. It would at least be easier than RF!

Nice clip!

[Charles Papert]

Good deal Aaron. Hardwired lens controls were the original deal (the third image down on this page shows one, along with a lot of great other images of the late great Panaglide system) but for obvious reasons have been superceded by radio systems. But hardwire is much cheaper and easier to build, and will work fine. If this is to be used with a stabilizer, try to use the most flexible cable you can between the motor and the controller.

Also remember that to be useful, they must allow the user to repeatably hit a mark by turning the knob to a fixed position, as opposed to a zoom control type of arrangement that can drive the lens in one direction or another. I forget the distinction, but I believe the first type is called a positional servo. Best of luck with your project!

[Aaron Shaw]

Awesome pictures! =D

That's actually the only part that troubles me - making the dial make repeatable marks. That and how to calibrate the thing for different lenses. Anyway, it's on the backburner until my anamorphic stuff works it's way out! I'm definitely going to be looking around at parts though!

[Charles Papert]

FYI, Aaron, the simpler versions of this sort of system require the user to dial in the end limits for a given lens manually. You have one knob for each end (close and far), and you start with them both in the middle.

Turn the focus knob to the close focus end.
Turn the close focus adjustment until you reach the end of the barrel, thus setting close focus.
Turn the focus knob to the far end.
Adjust the far end limit all the way to the other end of the lens.
The lens is now calibrated.

This is obviously a slower system than the automatic calibration on the Preston but also a lot cheaper.

[Patrick King]

Charles,
With recent advances in computer and electronic controls, wouldn't it seem like a relatively straight forward thing to build an Vari-Zoom controller with follow focus capability?

If the Vari-zoom had a way to record what the first focus setting was, what the final focus setting was, and the speed to move between them, then the operator would just have to initiate these settings to perform the desired rack focus. Sounds like a pretty easy thing for a LANC controller with a little onboard memory.

Am I daff in thinking that electronic capability could completely replace all this external equipment? I know of your background and experience, so please be gentle bursting my bubble.

[Charles Papert]

Patrick,

It's good to think about stretching the boundaries, and modern tech can indeed sometimes replace the tried-and-true. What you describe is pretty easy, and the XL2 has this sort of feature built-in. However, being able to rack between two preset points is a limited feature at best.

Let's assume we are talking about pulling focus for a 35mm optical system here, since it is far more critical than a straight-up DV setup. I'm talking about the Mini35, the Micro35, or any of the DIY systems that allow one to use 35mm lenses on a DV camera with the resulting shallow depth of field. Since most folks are fond of shooting with the 35mm lens wide open to minimize the DoF, the challenges of pulling focus are just the same regardless of whether there is a Panaflex or a Panasonic behind that lens.

Last night on set we were shooting a two-camera setup, and the B-camera was asked to do a take by themselves. To kill time, I watched our veteran B-camera assistant pull focus during the take. His eye was constantly scanning the two actors, whipping to the lens barrel to check the lens marks, back to the actors heads, down to their feet to reference floor marks, etc. etc. Very intense process, lots of "computational power". And a lot of human judgement as well, that "fuzzy logic" thing that involves anticipating where and how a person will move instead of chasing them once they get there. It reminded me for the umpteenth time how much respect I have for great focus pullers and what an art it is to be able to estimate distances down to mere inches from alongside the camera.

Incidentally, my assistant uses a Panatape, a sonar-based system that reports the distance with a readout right by the lens; however, he uses this as one of his tools to estimate focus, never relying by at as gospel.

To get back to the scenario you described: to be able to automate a rack focus would rely on the two subjects to be fixed, i.e. not alive! If your foreground subject is off by a few inches when you trigger your pre-programmed rack, you will end up with a soft shot. So you reprogram the end stop and try again. This time he's back on his mark, so the shot is still soft.

In other words; all the electronics out there can't replace the judgement and response of a human being who can pull focus. You need to be able to react instantly and intuitively.

As far as the actual controller, it really does require a mechanism that simply duplicates the effect of having one's hand on a gear-driven knob that delivers repeatable, direct results turning the lens to be really effective. The body mechanics sort of demand this.

Even with commercially available mechanical follow focuses, most assistants I know have very defined preferences. For instance, they may love the feel of the Arri but dislike the Chrosziel; love the Panavision but have issues with the Arri etc. And those are all high-end systems with little or no backlash, torque etc.

Hope this makes sense.