Correcting Ultra-Wide Keystone Effect in Photoshop
Ultra-wide angle lens for the landscape photographers are those heavy pieces of glass that we just can't leave at home. They can capture dramatic skies like no other lens in your collection. The problem with them is a distortion called keystoning where the pitch angle (see below) of the camera causes vertical objects to lean toward the center of the image.
Below is a typical example of keystoning that plagues me when using an ultra-wide lens. The lens is a Panasonic 7-14mm (this is the same as a 14-28mm in 35mm full frame sensors) zoom lens used on an Olympus OM-D.
Various Methods to Correct or Hide Keystoning
The methods we are going to explore are the following:
Clone Stamp and Healing Brush
One approach to removing the keystoning distraction is to use a combination of Clone and Healing brushes in Photoshop. Basically, we will be removing and converging objects from the image. Most of the time the healing brush works well but it may smear a section, or give you results that look obviously manipulated. A mixture of clone and healing brushes will usually give you pleasing results. The most obvious keystoning distractions in this photo are the towers and power lines; as can be seen in the image below.
The healing brush is a good option for the thin power lines. A good way to use the healing brush is zooming in to the pixel level (see below). This takes much longer but does work well.
Below you will see how I removed the large tower with the healing brush but the results were a bit splotchy.
We still have a few artifacts left so just hit it with the healing brush again in those areas. For this image the results were very good.
Below is the final image using only the clone and healing brush. This works pretty well but the image (trees and some clouds) still has that keystone look.
What do you do if there are more obvious vertical objects in the scene that you don't want, or can't remove?
Using the Lens Correction Filter
This is a very quick way to fix perspective in an image. Do not use the automatic lens correction filter but the one accessed by pressing Shift+Control+R (in Windows version). As shown in the image below; go the "Custom" tab and slide the vertical perspective slider to the left (minus) direction till your vertical objects are once again vertical. Since I am shooting with an ultra-wide zoom even moving the slider all the way to the left (-100) my vertical objects are still keystoning. Click OK and return to the main Photoshop screen. I like to use layers so I can see my progress and also go back to various steps if I need to tweak something.
Copy the layer and make your final vertical perspective correction (see below) and click OK for the corrected image. I could then remove the power lines if I wanted to but many times I will leave them.
See the final image below and you will see that the image no longer has the keystone affect but you can see that I lost some of the image on the side. How do we keep most of the image that was originally shot and lose the keystone affect? To do this we are going to use the Photo Merge tool.
This next process has to be preplanned at the time of exposure. Because I am an old school photographer I shoot about 95% of my landscape work in manual mode, which is essential for this process. I will now take two separate images and merge them together. If I was to shoot these images in an automatic exposure mode on my camera, the two images could have different exposures, which would be very obvious in the merging and could cause some extra work trying to balance the images.
I take one photo (the one I used in the previous example) showing all the sky that I want to include. The next image is taken with the horizon in the center of the frame. Because my camera is no longed tilted the keystone effect is eliminated.
Below you can see the two images I want to use in Adobe Bridge.
Having selecting both images in Bridge I open them up in Adobe Camera Raw (you can open up jpegs in Adobe Camera Raw) and at this time I am only going to remove chromatic aberration and perhaps a little sharpening. It is important that whatever you do in one you do the same in the other so select the "Select All" button in the upper left corner. Save these files. You can also skip this step and go straight to the next step and work on tweaking the final image later.
Go back to Photoshop and choose: Automate - Photomerge (see below)
Browse for your files, select Auto (default), Blend Images Together (default) and Geometric Distortion Correction. Press OK. (see below)
Wait a few moments for Photoshop to do it's magic and below is the result!
Below are the two layers Photoshop created
Because I like to go back incase I make a mistake I will now duplicate the layers and then merge the duplicates. Now that the layers are merged I can crop the images to my liking. There were a few spots in the sky that I wanted to keep so the crop had a couple of empty areas on the bottom. (see below)
Below I used the clone brush I fill in the blank areas being careful to make sure there are no repeated patterns.
Below is my original image
Obvious Keystone Vertical Objects Removed (below)
Using Vertical Lens Correction (below)
Using Photo Merge with two purposely taken images.
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