This type of image is caused by the photo chemicals in the eyes. It is different than true visualization. It is however a great way to start. You can always get this effect by standing in a dark room then while looking at where the light bulb is, suddenly switch it on and look at the light for about three seconds. Then shut the light back off. Now if you sit and close your eyes you see an image of the bulb. Try watching it as long as you can. The next time try to make it change color or shape.