FILM SPEED
Why is film italicized? Why if I am a digital photographer am I even mentioning film speed? Even digital cameras are effected by the dynamics of selecting the proper film speed or as it is now referred ISO equivalent.

Film speed, whether determined by the physical roll placed in a traditional camera or a setting on a digital camera, effects the range of shutter speed and the graininess/noise in the photograph. Here the digital photographer has a distinct advantage in that they can change the film speed setting on every shot.

Ideally, as a photographer you want to use the slowest film possible to capture your image sharply (of course unless you wish to intentionally blur an image).

Observe the picture of the erwy. Unfortunately when I took this photo, I had the film speed of my digital camera set to an ISO of 200. Given the poor lighting conditions, this was not high enough and therefore the resulting photo was blurry. In contrast, the photo of the race walker was taken with the equivalent of ISO 400 on a bright sunny day. Not only was this image super sharp, but other images taken at the same location actually allowed you to read the time on the race walkers watch.

INTENTIONAL BLURRINESS As previously mentioned, sometimes having a blur is effective. Observe the Burmese girl on the right as she sifts rice. While her face and body need to be sharp for the photograph to be effective, having the rice blur to show motion adds a cool effect to the shot. Using an ISO equivalent of 200 enables the slower moving girl to be sharp while the faster moving rice blurs.