Adobe Photoshop provides editing tools that make it possible to add all kinds of visual effects to your pictures. Cropping and trimming tools allow you to change the size and focus of your pictures, while the lighting tools allow you to correct poor lighting or add lighting effects that make your picture take on new life. If you would like to make one side of a picture dark and the other side light, for instance, you can do so with Photoshop's lighting tools.
Launch Adobe Photoshop on your computer. To launch Photoshop on a Windows computer, go to the "Start" menu, click "All Programs," click the "Adobe" folder and then click on "Adobe Photoshop." On a Windows computer, click on the "Finder," click "Applications," click the "Adobe" folder and "Adobe Photoshop."
Open the picture that you want to edit in Photoshop. Go to "File," click "Open," find the file in the window that comes up and double-click the file to open it in a new Photoshop window.
Isolate the side of the picture that you want to make dark. To isolate the part of the picture, click the "Rectangular Marquee Tool" from the "Tools" bar, click on the picture with your mouse and hold down the mouse as you drag it to form a rectangle around one side of the picture. If you want the picture to be split exactly in half, use the toolbar at the top of the window that the picture is open in to find the exact centre.
Go to the "Image" menu, hover over "Adjustments" and choose "Brightness/Contrast" to open the "Brightness/Contrast" tool. Move the slider under the "Brightness" heading to the left to darken the selected part of the picture. You can also move the contrast to the left if the picture becomes hard to see once you darken it. When the selected half of the picture is as dark as you want it, click "OK."
Click the "Rectangular Marquee Tool" again and this time draw a rectangle around the other side of the picture. Return to the "Image" menu, choose "Adjustments" and "Brightness/Contrast."
Move the slider under "Brightness" to the right to lighten the selected side of the picture. Moving the "Contrast" to the right as well can bring sharpness back to your photo if it appears too blurry once lightened. Click "OK."
Go to "File" and choose "Save as..." to save the picture. If you would like to save the project in case you need to work on it again, select the "Photoshop (PSD)" option. If you would like to save the picture as an image file, choose "JPEG" or "GIF" as the "Save as type." Enter a name for the picture in the box provided and press "Save" to save the edited file to your computer.
If the Photoshop toolbar does not automatically open on the screen when you launch Photoshop, go to the "Window" menu and click on "Tools" to display the "Tools" bar.