- Aperture - An aperture is a hole or an opening through which light travels. A narrow aperture will result in sharp focus. A wide aperture will have a sharp focus on the subject, but blur the surroundings or background.
- f-number - The f-number (aka f-stop) is the focal length divided by the "effective" aperture diameter. It's a dimensionless number that is a quantitative measure of lens speed.
|Aperture and f-stops|
- Exposure - The Exposure is the total amount of light allowed to fall on the photographic medium (film or digital image sensor) during the process of taking a picture. This can be a short period of time for a darker image, or a longer period of time for a brighter image. High Dynamic Range (HDR) photos use multiple exposures to obtain the HDR image.
Under exposure = Dark Image (Top Left)
Normal exposure = "Normal" Image (Top Middle)
Over exposure = Bright Image (Top Right)
3 Exposures combined = The HDR Image (Bottom)