Image Adjustments

Photoshop edits files in the following two ways. They are...

Destructive edits - changes modifying content in a way that it cannot be changed back to its original state. An example of a destructive edit would be to make a levels adjustment to an image by modifying a layer directly, thus altering it's content permanently.

Non-destructive edits - changes modifying content that modifies the edits rather than the original content. An example of a non-destructive edit would be to make an adjustment layer. Changes can be made to that edit, or adjustment layer without altering other layers or original content. A real world analogy would be walking outside and putting on sunglasses. In doing so you make the world appear darker without actually making it darker. Once you remove your sunglasses, everything is the same as when you put them on.

Destructive edits are BAD! They destroy data, which is information, which is ultimately resolution. Use non-destructive editing techniques whenever possible.

Here's a few types of Adjustment Layers you can add to your image using Photoshop. Please note, these are not all of them, we'll get to the rest later! If you only use adjustments layers to edit your images, you will be making non-destructive edits!

Levels - Adjusts the brightness and contrast using a histogram that represents the tonal values in an image.

Color Balance - Adjusts shifts of color in an image. If an image appears too blue you can make it warmer or more yellow using this tool.

Hue Saturation - Hue is the name of a color, saturation is a color's intensity. An image with no saturation contains no color information, only information on the brightness or darkness of each pixel. This tool adjusts the saturation of any particular hue in an image, or the overall saturation of all the hues.

How to make a New Adjustment Layer in Photoshop CS4?

Chose Layer -> New Adjustment Layer -> Levels (or any other desired type of adjustment from the list)