A while back a friend of mine was taking a picture in the dark using an external flash, whatever he did the final product either had three of me standing in the diffrent spots he told me to stand or he would snap the camera and then have me use a light to write something and the final pic would show me standing as normal with the word spelled out in the light I created. what is this technique called so that i can learn how to do it? also can this be done in daylight conditions?