Before I talk type about Exposure modes I need to make sure you understand the two components of exposure. Every picture you take, whether film or digital, involves Aperture and Shutter Speed. The two work in tandem to allow the proper amount of light to hit the film of sensor.

Simply put, the Aperture is an opening in the back o f the lens. It can be made big or small, letting in a lot of light or just a little. Depending on the lighting conditions you’re shooting in, you or your camera adjust the Aperture. bright sun – small opening. Indoor, low light – big opening.

The size of the opening is referred to as an Fstop or F number. You’ll see these noted as F2.8 or F5.6 or F16. Each step up or down the scale of F numbers will double or halve the amount of light coming through the lens. Contrary to what you may think, a smaller number is a bigger opening. The natural Fstop numbers are as follows:
1.4/2/2.8/4/5.6/8/11/16/22/32/45 (and so on)

The Aperture also controls Depth Of Field. DOF is the amount in front of and behind your focus point that will also be in focus. Smaller openings (F11,16,22) give more DOF; larger openings (F4,2.8,1.4) give shallow DOF. Controlling the Aperture allows you to intentionally blur the background or get a lot in focus from front to back.

Enough of this for now. My head hurts. Tomorrow we’ll cover Shutter Speeds. As I discuss the Exposure Modes in the next week I’ll cover more about how Apertures and Shutter Speeds affect how your pictures look.