Any ideas for a homemade focus puller...

[John Jay]

Hi

I have asked Chris to host the pictures referenced above

I expect they will be up shortly



PS --- the village photos seem to be ok today

also I found a cheap laser which may be just right - although a shorter one would be preferable

http://www.allelectronics.com/cgi-bi...506&type=store

[Patrick MCMurray]

to back track a little off topic...
after 2 or 3 weeks of gillian eating the coconut radio and other ways of screwing up the professors fool-proof plans, the fourth episode would be either <to use a very played out joke> him being voted off the island, or more real than reallity tv, a lynch-mob. next episode, they all go home and say gillian died in the ship wreck. END OF SERIES!

[Kevin Maistros]

I have an interesting idea I've been working on for creating a home-made follow focus system for the XL-1s 16x manual/servo lense. So far, I've only come as far as creating a very cheap and inexpensive dial. So cheap it's beautifull, and looks just like the real thing, with just as much functionality.

For the marking dial, I used the end of a cardboard tube package. Sort of like the white plastic end of a tootsie-roll piggy bank, but a bit wider and without a slit for coins. I then screwed in a knob I got from an old broken office chair. Nice big black knob, with a screw that goes back.. making it very easy for any future rigging to whatever system I come up with to act as gears.

I have also, a very cheap nd practical way to create a mount to span between the two support rods and hold it in place. However you create the gears, you can mount the system to the support rails below by creating a train-track mount. Basically, the support rods act as the rail road, and you're creating the wheels for the train tracks.. like how they lock in on the inner sides of the rails.

Ghetto Text Diagram:
_______
O| 8 |O

The top line is a piece of metal that goes on top of the two rails. it has a hole in the center for a screw to tighten the symetrical lower piece up and down together, clamping the support rods. The "|" marks are adjustable vertical pieces that hold against the inner-sides of the rods. These pieces can be found at your local hardware store or even in Erector sets (usually great for homemade things like this) Anyway, the piece is a horizontal to vertical joint fastener. In the shape of an "L". You'd put the top and bottom plate on, barely screw it in.. place the L backets between them.. slide them to the left and right and then tighten the brackets to the top piece.. followed by tightening the bottom and top pieces tight.

This should be able to create an easily hardware mountable, cheap solution to fixing whatever system you create to the support rods below.

Anyone have any ideas as to the actual follow focus gears and part to make the focus ring turn? Lets try to make this as super super cheap as possible.

[Mike Rehmus]

Don't use gears, use a kevlar-filled toothed belt. You can get any length and cross-section. No lost motion either.

[Rob Lohman]

Why do you say "don't use gears", Mike? Since if I'm not mistaken
I see them being used all the time on "pro" gear. Ofcourse that
should not mean we have to do it the same, but I was just
wondering why...

[Mike Rehmus]

Geartrains have some inherent problems:

1. They have backlash unless you use some special systems with springs to prevent the problem.
2. Have to be kept clean. Either you clean them often or you enclose them.
3. Are somewhat expensive since you have to have a matching gear on the lens. Either use the gear molded onto the control ring (if it has one) or make a gear ring that clamps onto the lens control ring.
4. Can have temperature-related problems at the extremes.


A Kevlar-filled belt, OTOH:

1. Stretches less than steel (that's what they use to drive printer heads).
2. Will turn corners (talking about the instrument-sized belts here).
3. Does not need matching gears on the lens control rings as the friction between the belt and the lens control is sufficient.
4. Doesn't have backlash issues.
5. Doesn't have temperature-related problems in normal operating environments (If you can survive, so can the belt).
6. Is much more tolerant of dirt.

These characteristics are true of properly engineered designs.

What amazes me is that the traditional design, with the focus-puller required to be right there next to the camera hasn't been replaced with a simple stepper-motor drive for the functions. Can be the same 'feel' as a direct-drive setup and the puller could be sitting or standing almost anywhere. But not with hands on the cameras which must force some limitations on camera movement.

[Rob Lohman]

Steadicams have such remote controlled focus devices, Mike.
I'm assuming there is a good reason why they are only used
in that specific field.

[Mike Rehmus]

I'm certain it is primarily one of, 'that isn't the way we've done it before.' Which is a good reason.

And, given the price of Hollywood-level gear, it is bound to be more than the existing tools since they already exist.

[Rob Lohman]

There is a great quote that comes to mind

Kind of like the young daughter who was watching her mother prepare a ham for baking. The mother sliced off both ends of the ham, placed it in a baking pan, and slid it in the oven. Wondering if the ends of the ham, which looked perfectly delicious, were harmful to eat, the daughter asked her mother why she removed them. "I don’t know," said the mother. "That’s the way my mother prepared a ham. Let’s call her and find out."

The mother rang up the grandmother and asked her why she cut off the ends of a ham before baking it. The grandmother replied, "That’s the way my mother prepared a ham."

Determined to get an answer, the mother called the great-grandmother and asked her why they’d all been taught to cut the ends off a ham. She replied without hesitation and with a smile in her voice along with a little chuckle......

The reason that she cut the ends off of the ham was because back in the early days of their marriage she didn't have a pan big enough to hold the ham. They couldn't afford to buy a bigger pan either. So that was the only way to make the ham fit in the pan.

[John Gaspain]

[they have really big pigs in the Netherlands?]

:)

Btw, I ordered a Zylis jar opener which im gonna modify. Should be here anytime soon.

[Rob Lohman]

Didn't you know? <g>

[Justin Burris]

For anyone interested in a stepper-moter focus puller that might be somewhere near our price-range:

http://www.dvxuser.com/cgi-bin/DVX/Y...num=1074845388