Correcting Exposure in Photoshop

There are two basic tools in Photoshop for correcting exposure:

Levels dialog - used for maximizing tonal range and rough brightness adjustments.
Curves dialog - fine tuning the tonal balance and contrast.

When viewing the histogram of an image, if the left side (shadow) ends abruptly this means that the image was "clipped" and that the darkest areas of the image will be rendered as solid black. This happens when the darkest areas of an image are below the image sensors detection range.

The Levels dialog is a quick and easy way to adjust the exposure of your image. Open the Levels dialog by selecting Image...Adjustments from the menu. From here you can either do Auto Levels or Manual Levels. The Auto Levels command will automatically stretch the histogram so that there is a better distribution from shadows on the left to highlights on the right. If you prefer to have more control over the results, you can use Manual Levels. With Manual Levels, you adjust the sliders under the histogram until you get your desired results. Typically, when adjusting an underexposed image you will adjust the middle and right sliders.

Basic Lens Components

Mount
Indicates what lens mount the camera has.

Aperture Ring
Controls the amount of light reaching the film or light sensor. Cameras that don't have an aperture ring often have an electronic control to adjust the aperture.

Depth of Field Scale
Indicates how much of the subject will be in focus.

Focusing Scale
Indicates the distance from the subject.

Focusing Ring
Used to focus on the subject when in manual mode.

Bayonet Ring
A threaded ring to attach filters.

Filter Thread
A threaded ring at the front of the lens for attaching filters.

Zoom Ring
For adjusting the focal length.

What is... "Stopping Down"?

"Stopping down" is when you decrease the amount of light reaching the light sensor by reducing the lens aperture. This will in turn increase the depth of field.

What Is... AF Lock?

AF lock stops your camera from autofocusing after your subject is in focus. You should first focus on your subject and then recompose the shot.