Exposure explained: aperture, shutter speed and ISO

For anyone browsing HubCage, here is a clear starting point on the subject.

Exposure is the amount of light that reaches the camera sensor, and three settings control it. The aperture is the size of the opening in the lens; a wider opening lets in more light and blurs the background. The shutter speed sets how long the sensor is exposed; faster speeds freeze motion. ISO adjusts the sensor’s sensitivity, with higher values adding visible grain.

Changing one setting usually means adjusting another to keep the same brightness. A good way to learn is to use the semi-automatic modes: choose the aperture yourself and let the camera pick the shutter speed, then try the opposite. Take the same scene several times with different settings and compare the results to see how each choice changes the picture.