Quick image rotation via cropping.

OK, I'll add a short little tutorial. I learned this one when I worked at a graphic design firm. Not being a designer myself, I was stuck with a lot of little annoying jobs that the designers didn't feel like doing. If you're new to photography / Photoshop, hopefully this will help you out in the future. I still use this years later because of how quickly it can get the job done.

One of the jobs was taking new photos of greeting cards and straightening them so they were square with the sides of the images. This technique is perfect for straightening images with 90 degree angles, or with horizontal or vertical lines.

Since the 90 degree angle happens a lot with human made objects (buildings in particular) this can be applied to the majority of non-nature images out there.

Here's the original image that I want to straighten.



It may not be clear at first that an image needs straightening, but break out the crop tool and put it next to a vertical line (in this case, the edge of the pillar), and you'll see that the image is rotated by a degree or two.

There is an image rotation tool in Photoshop where you can tell it to rotate the image by exactly 3 degrees clockwise, but it is both slow and inefficient. This technique will save time and is very exact.

But why the crop tool? It's fast and nearby. Plus it's in nearly every photo editing program out there, and this technique can be applied almost universally.



As you can see above, I choose the pillar as my reference line. This will be the most important step of the process. Due to the funkiness of human vision, we can look at lines and see them as straight or parallel even when they are obviously not, and vice-versa.

My first attempt at this was to use the hand railing in the background, or the lines where the shop widows touch the wall. I assumed that these lines would be nice and horizontal, but I was quite wrong because of perspective.

The longer the reference line the better, but be wary of any lens distortion that could make the lines curved.



The next step is shown above. We need to rotate the crop tool to line it up with the vertical line of the pillar. To do this, I put the top left corner of the crop tool on top of the reference line. Then I moved the center mark of the crop tool to the upper left corner. This will allow me to rotate about that corner. I then rotated until the crop tool lined up with the reference line.

Remember, if you are using a reference line near the edge of the image, the crop tool may snap to the edge. When this happens, hold the Control key down to temporarily disable snapping.



Here I have zoomed in on my crop to make sure it is lined up with the pillar. I also moved the other edge of the crop tool to the stair in the lower right corner. This is to double check that the crop is correct. The vertical line of the step it lined up correctly. The horizontal line is not correct, but that is because of perspective again.

The last step is to move and resize the crop tool to you liking. You can either crop to your final image, or you can drag the crop tool past the outside of the image. This way you can have a straightened image without removing any of the original.



This is the final crop. Compare it to the first image and you can tell that it is straighter. The first image probably wouldn't have been that bad, but straightening it out still makes it look better.