Straight and Level
I’ve been known to be a perfectionist. One thing I strongly believe in is properly leveling photos. I’d actually call it an obsession. Perhaps it’s related to my self-diagnosed case of obsessive compulsive disorder, but I spend a great deal of time in post processing checking and rechecking my photos to make sure they are level. I will literally go back and forth .1 degree of rotation at a time until I am satisfied. I will step a few feet away from my computer monitor to get an overall impression from a distance and I might step away completely for a few minutes and return with a fresh set of eyes. Bottom line is, I think leveling is very important and is the first step in a quality shot. Now of course, there are certainly times when you might want to have an angled composition. That’s something entirely different. I’m talking mostly about landscapes and any other circumstance where a photo is presented in a way that suggests it should be level with the horizon.
Some of the latest DSLRs are coming equipped with a built-in digital leveler. My Canon 7D has this feature and I use it routinely in conjunction with live view when setting up nighttime shots on the tripod. It’s a great starting point. You can also get a small cube that fits in the flash shoe that contains a small air bubble to help guide your camera to a level orientation on a tripod. Those are great tools to start with at the time of capture, but there are various ways in post-processing to rotate and level photos. I use Photoshop CS5 so I will mention some different methods.
What’s important when leveling photos is to choose good references. A good place to start is to look for reliable verticals. Anything that stands straight and has a straight edge that can be used as a guide. If there is a light pole and you know that light pole is straight in real life but in your shot it is leaning, you know the shot needs some rotation to get that pole to appear perfectly straight up and down. However, the most reliable verticals are going to be in the center of the frame because lens distortion, especially UWA or fisheye distortions, will cause verticals to lean or bend in the outermost portions of the frame. Some other verticals I like to use are the sides of buildings or any other structure that has a straight edge that can be checked.
In addition to vertical references, look for good horizontal references. Horizontal references can be less obvious so I think it’s easier to start with verticals, and then find horizontals that can be used to cross-check your verticals. If you can get both vertical and horizontal references to agree that the photos is level, then you’re good to go!
Once you find reliable references you can choose a couple different methods to rotate the shot. The first method is to rotate the image in conjunction with the crop tool. When you crop, you can drag the corners to rotate the shot. This is nice because it crops at the same time but I struggle with the accuracy using this method because it’s not exact and it’s hard to see how it will look until after you execute the crop.
The next method that I use as a more accurate starting point is the ruler tool. It can be found by right clicking on the eyedropper tool in the menu to the left.
This tool can be used with a vertical or horizontal reference by clicking on one side of the reference and then dragging to the other side of the reference. So if you were using a light pole, click the base of the pole to anchor that point and then drag and release at the very top to anchor your second point. What you are doing is drawing a line along the reference. In this shot, I use a horizontal reference based on the shape of the fountain.
You can see that the line slopes up from left to right confirming that this shot needs clockwise rotation. Then by going Image—>Image Rotation—>Arbitrary a box opens up with a number in degrees and selection for CW (Clockwise) or CCW (counterclockwise).
Since we used the ruler tool, Photoshop calculated how much and what type of rotation is needed. In this case, it determined the shot needs .57 degrees of clockwise rotation. I use this as a starting point and I might tweak it further by plugging in my own values until I am satisfied. So if .57 degrees got it close, but I feel it needs another .2 degrees, I will open the Arbitrary box again and plug that in and see how it looks. I continue the process until I am satisfied.
Like I said, I think a properly leveled photo is important. Here is the final photo!