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"painting" on film with light and lasers?


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#1 Pedro Padilla

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Posted 13 February 2006 - 07:50 PM

Hi all-

I had an idea for an experimental film recently, and I wanted to run the idea by the board to see if anyone had thoughts or suggestions on pulling it off.

Basically the idea is to run 16mm film through an old turrent lens Bolex with the turrent turned all the way around to expose the gate. (This would need to be in a dark room, obviously!) Then I would use a laser pointer and some tungsten bulbs and film lights as shot through a pin hole or a thimble or other masking devices directly onto the running film. The desired effect would be to "paint" vertical lines and different patterns across the film and hopefully get something like a neon Stan Brakhage film.

I asked a film tech guy I know about this and he said two big factors would be how fast I was running the film and the wavelength of the lasers I was using. After a little wikipedia digging, I found this info:

-US laser pointers do not exceed 5 milliwatts
-red laser pointers operate with a 650/670 nanometer wavelength

I'm a student, so I have a choice of three film stocks:

a) An old Kodak intermediate stock, 7243, we're guessing the ASA is between 6 and 12

B) Kodak 200T

c) Kodak 500T

Any info related to exposing laser light or exercising controlled direct exposure like this would be appreciated. Thanks a bunch in advance!
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#2 Jamie Metzger

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Posted 13 February 2006 - 09:35 PM

What school do you go to?

At first though, you might want to use the 500T to have that lattitude for exposure. I don't know if a light meter will read a laser correctly, nor do I know if the beam is like footcandles; falling off the further the light is from subject.
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#3 Robert Edge

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Posted 13 February 2006 - 10:10 PM

Pedro,

If I understand your post, you are talking about a technique called painting with light.

It has been used by experimental still photographers and also it has been widely used in the advertising industry. Indeed, there is a commercial device that is used for this purpose that employs fibre optics, called a "hose".

Some of the most interesting painting with light work has been done with ordinary flashlights. There are also people who have combined painting with light and a camera with a flexible bellows between the camera body and the lens that is moved around during the shot.

You may find it useful to look up "painting with light" on the net.

If I correctly understand what you are planning to do, you may also find it useful to experiment with a still camera before you blow a lot of motion picture film. It is a very hit and miss process unless you have experience with it. There's a fellow with whom I have corresponded by e-mail, who uses both painting with light and a flexible bellows, who has told me that it took him a long time to amalgamate both techniques to produce a book that he has published.

Speaking only about painting with light, one of the most impressive examples that I have seen is of a man standing on the roof of a building in New York. I don't recall the name of the photographer, but he is well known (except to me at the moment), and you should not have a lot of trouble finding the photo on the internet.

Best of luck with this.
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#4 Dominic Case

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Posted 13 February 2006 - 10:44 PM

Camera negative sensitivity starts to fall off at around 670nm, whereas the intermdiate stock goes up closer to 690nm (though it's a lot slower of course). Sounds as though you could be in business.

Exposure is hard to judge and hard to meter: remember that if you are moving the laser spot around, then the exposure time on any part of the film emulsion surface won't be the usual 1/48th sec, but the actual time that the spot is on that bit of film - which could be a lot less. The faster you move the laser, the less exposure on the film.

Also, don't forget that your film won't be running continuously, but intermittently - so the patterns you get from moving the laser beam around the gate will be very disconnected.

THe intensity of the beam will be dependent upon the size of the spot. Inverse square law works if a beam doubles in diameter at twice the distance from the source - ie if it is cone-shaped. If it is truly parallel, then the intensity remains constant at different distances.

It is theoretically possible to work out what sort of exposure you will get - but much much too hard unless you want to start aloowing for the size of the spot, converting milliwatts to lux, and so on. Easier to try it out. To get a sense of whether it will work at all, you won't need a camera - just stretch a bit of rawstock out on a bench (in a darkroom) and wave the laser over it. Then get it processed.
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#5 Dickson Sorensen

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Posted 13 February 2006 - 11:09 PM

A little different but interesting never the less. I once experimented with a shot where I shot stop motion of a guitar player. The subjuct moved a tiny amount during dach exposure in a dark room. The shutter would be open for the exposure and a person dressed in black circled the perimiter of the subject's body with a small light pointed into the lens. Each exposure took about 20 seconds to complete then the light was switched off and the film advanced to the next frame. It took all night to produce about 20 seconds of film.
the effect was a wildly moving streak the shape of the guitar player. It looked fantastic. Good luck with your test.
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#6 Robert Edge

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Posted 14 February 2006 - 12:09 AM

Pedro,

Now that I re-read your post, I realize that you are talking about using light to write directly on a frame of 16mm film.

I'm curious to know what you think the difference is if you use the camera and film to record the effect of light on a panel lit from behind, giving you a larger surface on which to manipulate the light.
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