A simple technique once or twice done and you will be the rotation master. Open an image file that you need to rotate.

Test Image

This is the image that will be used in the tutorial. This shot was taken in San Diego, California at a historic military graveyard. It was near dark and as you can guess, I didn't use the bubble level that I carry with me. I prefer to think that even with the level on the hotshoe of the camera, it was too dark to see the bubble. I almost belive myself with that story. The Grab a copy of my image if all your images are straight!

This image will serve as the original for this tutorial. Right click to download if you want to duplicate this tutorial on your own.

Find an element that you believe to be vertical or horizontal

A classic, easy reference is a horizon over water. This is why I chose this image to show you this technique although you may certainly use any reference in your image. One reference often overlooked is a reflection in water. Imagine your friend standing on the far side of a puddle. You can use his nose in the reflection and his actual nose as your two endpoints. If you don't have any friends, a treetop on the far side of a lake, and it's reflection in the lake will work as well. In photoshop, select the measure tool. It looks like a little ruler. If you right click the eyedropper tool, you can select the ruler tool in the flyout menu. Once selected, pick two points on your picture that you believe to be horizontal or vertical. My suggestion is that you pick two points as far apart on that line as possible. To select those two points simply click on each end. A line will appear that looks like the one in the image below.

Select your points with the ruler tool. A click on each end and a line connecting them will define your horizonal ( or vertical ) element.

Photoshop will perform the rotation for you!

This is my favorite part of the job. Photoshop will automatically perform the rotation for you because you have told it what should be level. Use the command: Image|Rotate Canvas|Arbitrary. A dialog box will show up with the recommended rotation. Accept it and you will see the image. If the rotation doesn't look good, undo the rotation and start again with the ruler tool. Notice the four triangular white areas on the outside edges. The color of this area comes from the background color selected prior to the rotation. If you pick a background color that is easy to see it will make the next step easier.

Image|Rotate Canvas|Arbitrary is the command that will get you here!

Crop and you are done!

Use the crop tool to remove the four triangular areas on the perimeter of the picture. The crop tool is on the toolbar or you can use the "C" button on your keyboard as a shortcut to select this tool.

Done - I hope you had fun and learned a trick here today.