Join Tim Grey for an in-depth discussion in this video Straightening a crooked image, part of Photoshop CS6: Image Cleanup.
When we have a subject that includes horizontal or vertical lines, it's often very important to make sure that those lines remain perfectly horizontal or vertical, so that the image looks correct. Many cameras include a built in level feature. You can also put a bubble level into the flash hot shoe for example. Or of course, you can just eyeball the view through the viewfinder, and adjust the camera position to ensure that horizontal or vertical lines remain perfectly straight. Of course I'm sure you can appreciate that in this case I have intentionally rotated the image, so that we had a crooked line. I simply couldn't find an image of my own that had a crooked horizon. At least, I hope you might consider believing that. In this case though, we have some lines that are very obviously intended to be horizontal, but they aren't.
The steps here, the lines ought to be perfectly horizontal. Let's take a look at just how easy it is to correct a crooked horizon or other horizontal or vertical line, using the Crop tool. I'll go ahead and choose the Crop tool from the toolbox. And then I could drag the crop box into the image, so that I can adjust the image manually. Pointing my mouse outside the image and dragging until the image appears perfectly parallel to the lines. Now when I'm rotating, you'll notice that a grid display shows up, and that makes it reasonably easy to evaluate the result.
I can then adjust the outer edges of that crop box making sure that all four corners fall inside the actual image area. But it actually can be a little bit easier than this. I'll go ahead and press Esc to cancel that crop. And then on the options bar with the Crop tool selected, I'll click on the Straighten tool. Now I can simply click on one end of one of the straight lines, in this case one of the steps and then drag across the image. You'll see that this gives me a line which I can align with the straight edge, in this case the top of the step in the image.
I usually try to make that line as long as possible, just because it makes it a little bit easier to evaluate, and helps make sure that I'm getting the most accurate results possible. And then when I release the mouse, you can see that the image is rotated automatically, so that the line that I identified with the Straighten tool, is now perfectly horizontal. Notice by the way, that the cropping of the image by default automatically fell inside the image itself. I could certainly fine tune each of the edges or corners of the crop box as I see fit.
But generally speaking, I want to include as much of the image as possible without going outside of the actual photos so that I don't have any empty pixels showing within that crop. So that looks to be a great result. Notice also I'm leaving the Delete Cropped Pixels check box turned off. That way, the pixels that fall outside the crop box will not actually be deleted. They'll still be outside of the actual canvas area for the image, so that I can always get back to them later if need be. But this looks to be a good crop and more importantly, a good straightening of the photo, so I'll go ahead and click the Commit button on the Options bar. And you can see that because I had the Delete Crop Pixels check box turned off, I no longer have a Background Image layer.
The layer is now called Layer zero, because the background has been converted to a normal image layer. That's perfectly fine. That's part of this nondestructive process of cropping. I can always get all of the pixels back by choosing Image > Reveal All. But in this case, I think we have a good result. So I've straightened that photo very quickly and easily using the Crop tool.
- The ethics of cleanup
- Reviewing the image
- Nondestructive cleanup
- Cleanup tools and techniques
- Removing strong color casts
- Gradient adjustments
- Extending the frame
- Using multiple exposures to remove subjects from an image