Instructables
Picture of Light Writer
Have you ever tried writing in the dark? Even something as simple as your own name might turn out looking like you were writing in an earthquake. I
Materials
Tape
LED light
Watch battery
Digital camera with adjustable shutter speed or exposure

Hypothesis:
I don't think that we can write in the dark

Lets see
 
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Step 1: Experiment

Picture of Experiment
2.jpg
I knew there had to be a better way, and after a bit of time I came up with a beautiful and amazing solution – Light Writer. It's a phenomenal trip into the world of optics, photography, and fun.

1.Make sure your LED light is working properly.
2.Place one LED wire on the negative side of the watch battery and the other LED wire on the positive side of the battery.
3.Squeeze the wires against the battery and the LED light should light up.
4.Repeat step 2, but this time tape the wires to the watch battery.
5.Set your digital camera to a slow shutter speed or to a setting for a long exposure.
6.Set your camera timer or have a friend take a photo.
7.Take the shot and write a message in the air using the light. Make sure the light is facing the camera.
8.Don't forget to write your letters backwards in the air! Otherwise, you are going to end up with a backwards message in the photo!

Step 2: How Does It Work?

Picture of How Does It Work?
The key to writing the message is in the camera settings. You may have taken a picture of a light before with no real magic showing up in the photo. When you adjust your camera to a slow shutter speed/long exposure, you allow the shutter inside your lens to stay open longer. While the shutter is open, it allows light through the lens. With the longer exposure, the shutter allows the lens to view the light for the entire time you are writing your message. At a regular shutter speed or exposure time, the shutter only allows the lens to view the light for an instant.