Originally Posted by Wolfgang

The F# represents aperture. All lenses have a series of blades in them that open or close.


A low F stop (f/1.8) the blades are completely open allowing the most light to hit the sensor (or film) This creates a very shallow depth of field.

A higher F stop (f/36) the blades are almost all the way closed this allows little light to hit the sensor so longer shutter speeds are needed to get the right exposure.

With a high F stop the Depth of field will be much greater. For an all around decent Depth of field I shoot between F/8 and F/11.

Photographers such as Jerry Uelsmann and Ansel Adams would have such a high F stop that their exposures could take hours for one shot and everything would be in focus. But this also has to do with the ISO or speed of the film. But that's another topic.

Let me know if I'm making any sense.