One of the things that fascinates me very much in digital photography is using hardware filters, like polarization and infrared filters. Especially the latter is very interesting, because these filters cut off wavelength below 720nm (depending on the actual filter). Infrared digital photography differs a lot from infrared film photography. We have no idea about any sort of color in the infrared as it is just black for us, but the camera assigns a color automatically. And there begins the fun. In addition, you can create wonderful dramatic images and look at the sun during the day when there is a partial eclipse.