[COLOR=darkgreen][B]No.4: [/B][/COLOR][COLOR=black]Auto, P, A, S, M, and iAuto modes explained.[/COLOR]

The P, A, S, M exposure modes are pretty much the same, but Auto and iAuto modes can vary slightly:

[B][COLOR=darkgreen]P (Program):[/COLOR][/B] Historically, this mode represented the introduction of the ability for a camera to automatically alter the aperture and shutter speed at the same time. Previously, cameras were able to change the aperture or shutter speed according to the meter reading, but not at the same time. The reference to 'Program' refers to a microcomputer in the camera calculating the required aperture and shutter combination.

[COLOR=darkgreen][B]A (Aperture priority):[/B][/COLOR] This is where manual control priority is given to the photographer. You set the aperture and the camera will work out the shutter speed. This is occasionally labelled 'Av' and means Aperture value.

[COLOR=darkgreen][B]S (Shutter priority):[/B][/COLOR] This is the opposite to 'A' - so you set the shutter speed and the camera adjust the aperture automatically. This mode is also known as 'Tv' mode, which stands for Time value.

[COLOR=darkgreen][B]M (Manual):[/B][/COLOR] Quite simply, in manual mode, it's up to you to adjust the shutter and aperture yourself. With some cameras, this mode can still enable automatic exposure metering. Instead of varying the shutter and aperture, the camera's sensitivity (ISO speed) can be set to automatic.

[B][COLOR=darkgreen]Auto (Automatic):[/COLOR][/B] This varies by camera manufacturer. Sometimes this mode is denoted by a green symbol. But basically it means that the camera is completely controlled automatically - adjusting the aperture, shutter speed, usually the ISO setting, and white balance. Although serious photographers avoid this mode, it does have one valuable use. If you have been using a customised setting on one of the usual PASM modes, but you don't have time to reset them for the next shot, switch to Auto. It can be a life-saver.

[COLOR=darkgreen][B]iAuto (Intelligent Auto):[/B][/COLOR] This is the ultimate automatic setting for the latest generation of cameras and varies in complexity by manufacturer and camera model. Basically, the camera will not only decide shutter speed, aperture, white balance, and ISO speed, but the more sophisticated systems will analyse the scene and motion to optimise the settings further. Some cameras that use iAuto mode will select one of the camera's scene modes to match what it makes of the subject matter. Others will detect subject motion and alter the shutter speed and even ISO sensitivity to freeze action better.

[B][COLOR=darkgreen]Tomorrow:[/COLOR][/B] Depth of field explained.

[I]Incidentally, please don't hesitate to post a question about this Daily photo tip if you have one![/I]