Just a quick overview on the exposure controls on a DSLR (Digital Single Lens Reflex) camera. ISO, shutter and aperture settings.

SHUTTER controls the TIME the digital sensor is exposed to the light.

BULB setting allows you to hold the shutter open as long as you want. Pressing the shutter button opens the actual shutter curtain and releasing it closes it. This is used for long exposures for creative effect and often used for creating star trails in the night sky.

30 seconds to 1 second is represented in whole numbers and shutter speeds higher or faster than 1 second is represented in fractions even though your camera displays the readout as whole numbers. Example, 250 readout is actually 1/250th of a second.

APERTURE controls the AMOUNT of light entering the camera. The size of the lens opening is often referred to as F-Stops. Smaller the number = larger the opening. Lager the number = smaller the opening. Example, F1.2 is larger than F22 since 1.2 lets in more light than 22. "Stopping down" the lens just means you are selecting a smaller opening.

Depth Of Field (DOF) I Indicates the amount of sharpness from near to far in your scene in relation to the selected point of focus. Larger opening decreases depth of field and smaller opening increases depth of field. A shallow DOF is often used in portraits where your subject is in focus and the background is thrown out of focus which helps isolate the person from an otherwise distracting background. (F1.8) In a landscape scenic shot, a smaller lens opening (F22) is used to increase DOF which helps to keep near to far elements in focus. Some cameras have a Depth of Field preview button on the side of the lens to let you see how much of the scene is in focus from near to far, although the image through the viewfinder may look dim if the lens is stopped down to a smaller lens opening.


Three basic exposure modes found on most cameras:

(TV) shutter priority, you select the speed in which the image is captured while the camera adjusts the aperture to balance the exposure. When you want to freeze action or blur a waterfall, select shutter priority mode. 1/15th of a sec or slower blurs motion, but also requires a tripod to eliminate camera shake. 1/125th of a sec or higher freezes motion in varying degrees. TV stands for Time Value, not an actual television mode. :-)

(AV) aperture priority mode, you select the amount of light entering the sensor and the camera selects the appropriate shutter speed. If you want to control near to far sharpness or isolate a subject against an otherwise cluttered background, use this mode to control the amount of light and depth of field. F 4.0 or less opens up the lens and is ideal for portraits with pleasing bout of focus backgrounds while the subject is in focus. F 8.0 or higher is ideal for maximum depth of field or near to far sharpness which is well suited for landscapes. AV stands for Aperture Value.

In (M) manual mode you select both time and amount of light entering the camera. A built-in incident light meter guides you to the well exposed image. Since the meter averages light and dark tones to the 18% grey value, some scenes can be either over or under exposed. A scene shot at twilight can sometimes be rendered as if shot in the middle of the day since the camera "thinks" it is supposed to be "correctly" exposed for such. This is where the use of the exposure commpensation or manual mode comes in handy to render the scene as faithfully as seen by the human eye.

ISO (International Standards Organization) is the adjustable sensitivity of the digital sensor's ability to capture light, like the standard film speeds offered back in the day. Lower the ISO setting, the less sensitive it is to light and requires slower shutter speeds and wider aperture settings, but produces sharper images with higher color saturation. Higher ISO settings allows for faster shutter speeds and smaller apertures but the trade off is digital noise which can give the image a grainy effect.


Video shot with Canon PowerShot SD780IS Digital Elph ultra compact point and shoot digital camera in 1280x720 HD.