How to do writing with light photography?

iso doesn't really matter. i kept it down at 100. keep the flash off and set the camera to M. set the shutter speed to B. you'll need someone else to hold the shutter button down for however long it takes you to write. small flashlights or pen lights work the best as they provide a stronger light source than a glow stick can. you can try using one of the longer shutter speed setting like 30 seconds if you have no one to operate the camera for you. i did that with some success but it takes a bit of practice to get the timing down. also you'll need to operate in complete darkness for the best effect so make sure you have a clear path to walk in front of the camera. if you have an external flash fire it once during the exposure to capture you at one particular moment.