Logo - pSquared Logo - photography darktwitter facebook

Exposure compensation for available light is activated by changing the shutter speed and/or lens aperture. This is done by using AE L AF-L (Auto Exposure/Autofocus Lock) button or exposure compensation button, or by Auto Exposure Bracketing . In flash photography with a dedicated TTL flash unit, exposure compensation can also be performed by varying the amount of flash output.  Camera-originated exposure compensation affects both the foreground subject and the background; variations in flash output amount affect only the foreground.

Exposure compensation

Metal tubes used to obtain additional separation between the lens and focal plane.  Used in close-up photography.  They are fitted with screw thread or bayonet mounts to suit various lens mounts.

Extension tubes

The numbers on the lens aperture ring and the camera's LCD that indicate the relative size of the lens aperture opening.  For more information see our tutorial on f numbers and stops.

f number

A coloured piece of glass or other transparent material used over the lens to emphasise, eliminate, or change the colour or density of the entire scene or certain areas within a scene.


Ultra wide angle lens giving 180 degree angle of view.

Fisheye lens

The timing of the flash has to coincide with release of the camera's shutter.  There are two types of synchronisation:  front curtain sync which fires the flash at the start of the exposure, and rear curtain sync, which fires the flash at the end of the exposure.

Flash synchronisation

Light being reflected off, instead of transmitted through, a lens surface causes spots and a lack of contrast.  The use of multilayer coating of individual lens elements in a lens helps combat and minimise.  It is aggravated by unclean lens surfaces on front and rear lens elements or filters.