A long exposure photograph Physiogram 1 © 2016.
Ever seen a sand pendulum? They create Spirograph-like geometric lines (or Lissajous patterns) using...em, a pendulum and sand. Physiograms are very similiar to those, but instead of sand we use a light source and a camera to record the movement of that light as it swings. As with a Harmonograph, a mechanical device that creates geometric shapes, both gravity and momentum work wonders.
You don't need a lot of equipment to do the technique but you will need a camera (one which allows control of the shutter speed), a tripod (or secure surface to keep the camera still), light source/s such as torches (ones with a little weight to them are good for momentum), string and something to secure the top end of the string to, like a ceiling. Hooks and clips can come in handy too for securing the ends of the string. The work area should be quite dark, as a result the technique lends itself to night time, however a dark room works just as well.
Work in an area that is big enough to swing your pendulum and make sure your string is the right size for your needs. Too long and you might damage something or put all the lines out of shot, too short and you might only get a small amount of swing time (allow room for your light source to be safely added to the bottom of the string too). Secure the string at the top. I use a hook in the ceiling joists. Then fix the light source to the bottom end of the string. I tie the string to a strong clip and clip the light source in, it makes changing light sources easy.
You may want to experiment a bit with the height that you place your camera at, depending on how far the pendulum travels (I like to set my camera a low as my tripod will allow) and point the lens up. If the pendulum travels too far for the camera or the lens is not wide enough most of the lines may end up being out of the photo. I find it's best to place the camera directly under the ceiling hook. Choose a long shutter speed, again this may take a bit of tinkering but I usually begin around 20 seconds or above. Swing the pendulum and take the shot.
A long exposure photograph Physiogram 2 © 2016.
I attached more than one light source to the pendulum to create each of these images in this blog entry. Different colours are great, but if you try the technique, use whatever colour/s you want to.
Colour can be added to white light sources by using colour gels or, in some cases, sweet wrappers.
A long exposure photograph Physiogram 3 © 2016.
The kind of swing has a big impact on the image. The amount of momentum or the direction in which you send the pendulum can completely change the outcome. I relied on the direction and momentum to help create interesting shapes in the above photo.
The placement and the type of light source/s has a big effect too. I attached two constant colours (red and white) and a third flashing light which sat a bit further away from the other two torches. The flashing created a sort of hashed line as it moved. I used the same flashing light in the very top image.
A long exposure photograph Nuclear © 2016.
If you have enough room between the pendulum and the camera you can light paint by hand too. I have a home-made light stick that is great for this purpose.
A long exposure photograph Wings © 2016.
Once you are comfortable enough with the basics of the technique you can experiment. Try using different lengths of string, adding more than one ceiling / pendulum fixing, using more or less momentum in the swing, releasing the pendulum in different directions, using different combinations of light sources, spinning the pendulum, adding shapes to the pendulum (and then place light sources in different positions) and changing the camera shutter speed.
The above photo looks, to me, a bit like a butterfly and it's one of my favourite physiogram photos. One of the key things in creating the butterfly was the length of shutter speed, it was faster than most of my other physiogram photos.
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