Changing the size of the aperature (f-stop) affects how much light is allowed to enter the camera. This will have an effect on whether your photo is exposed properly, under-exposed or over-exposed. I'll post later a full explanation of this concept, but for now, here's an example. This photo was taken in the same place at the same time. The conditions outside were partly cloudy. All three images were taken with a shutter speed of 100 (1/100ths of a second). The first photo used a smaller aperature and, therefore, allowed less light to fall on the film (or in this case on the sensor). The second photo is taken at the correct aperature for that shutter speed according to the light meter. The third used a larger aperature, and therefore allowed more light in. None of the images has been retouched.

But, it's not just the amount of light that f-stops affect. We'll discuss f-stops and depth of field in another post.

	ISO: 200 Shutter Speed: 100 f-stop: 11 Medium: Digital
	ISO: 200 Shutter Speed: 100 f-stop: 8 Medium: Digital
	ISO: 200 Shutter Speed: 100 f-stop: 5.6 Medium: Digital