Aperture-An aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane.
Shutter-shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photograghic film or light-sensitive electronic sensor to light to capture a permenant image of a scene. A shutter can also be used to allow pulses of light to pass outwards, as in a movie projector or signal lamp.
Exposure-exposure is the total amount of light allowed to fall on the photograghic medium (photograghic film or image sensor) during the process of taking a photogragh. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance over a specifed area.
Depth of field-depth of field (DOF) is the portion of a scene that appears acceptably sharp in the image. Although a lens can precisely focus at only one distance, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
F-stop-of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens ; in simpler terms, the f-number is the focal divided by the ''effective'' aperture diameter. It is a dimensionless number that is a quantitative measure of lens speed, an important concept in photograghy.
Focal lenghth-of an optical system is a measure of how strongly the system coverges (focuses) or or diverges (defocuses) light. For an optical system in air, it is the distance over which initally collimated rays are brought to a focus. A system with with a shorter focal length has greater optical power that one with a long focal length; that is, it bends the rays more strongy brining them to a focus in a shorter distance.
                                                                -Krysten