Look Sharp 2
This one is all about photography.
On modern compact digital cameras, all the clever stuff is worked out for you. If you are serious about photography though, and/or you own a digital SLR, you can play around with apertures, shutter speeds and film speeds to create different effects.
Each string of numbers - e.g. 1516100 - is a shutter speed, an aperture, and a film speed - in photography these are known as stops.
To turn these into meaningful numbers, look at http://photonhead.com/beginners/stops.php