The Lens Corrections panel can be used to apply lens profile corrections to remedy geometric distortion. This can correct for curvature of straight lines, including photo- graphs shot with a fisheye lens. Such corrections are global, which means the correc- tion maps the entire frame area, reshaping it based on knowledge of the geometric distortion characteristics of each lens. While this can often help produce better-look- ing images, photographs shot using a wide-angle lens can sometimes benefit from selective perspective correction. This is because even when you correct for geometric distortion, objects toward the edges of the frame can appear elongated and round objects appear egg-shaped. This is where the Adaptive Wide Angle filter can be useful, as it allows you to selectively correct the perspective.
In this example, I photographed the Glenfinnan Monument using a 14 mm lens on a full-frame dSLR and had to tilt the lens up slightly to include all of the tower. By making use of the Adaptive Wide Angle filter controls, I was able to correct the con- verging verticals and ensure the walls and tower edges were all kept perfectly straight.
The Adaptive Wide Angle filter adjustment produced a unique perspective correction of the monument. But because I didn’t correct the top and bottom sections, this has created the impression the viewpoint is closer than it was in the original.
1 This shows the original photo- graph, which was shot with a 14 mm rectilinear lens using a full- frame dSLR sensor. I imported this photo into Lightroom, where I applied an Auto Basic panel adjustment and left Enable Profile Corrections unchecked in the Lens Corrections panel.
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2 I went to the Photo menu and chose Edit In ➯ Adobe Photoshop, where, from the Filter menu, I selected the Adaptive Wide Angle filter. With the Constraint tool selected, I added constraints to indicate which lines in the image should be made straight (these were colored cyan). For those that needed to be absolutely straight, I held down the S key as I did so. These were indicated with purple for the vertical lines and yellow for the horizontal lines. I also reduced the scale slightly before clicking OK to process.
3 Here is the final version, where I cropped the photo and filled in the four corners with a Content- Aware fill, using the same method that was described in the previous series of steps.
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Removing elliptical distortion
1 This photograph was shot using a 14 mm lens on a full-frame dSLR camera. Because of the wide angle, the bicycle wheel appeared as a stretched, elliptical shape.
2 In this step, I went to the Lens Corrections panel, where I checked Enable Profile Correc- tions and selected the Vertical Upright adjustment to improve the perspective on the buildings.
However, this happened to make the wheel distortion even worse.
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3 I chose to undo the correction in Step 2 and reverted to the Step 1 state. I went to the Photo menu and chose Edit In ➯ Adobe Photo- shop, where, from the Filter menu, I selected the Adaptive Wide Angle filter. Here, I selected the Perspective Correction method and added a number of vertical, horizontal, and regular constraint lines to correct the straight lines.
I then selected the Polygon Con- straint tool to define the shape of the bicycle wheel and clicked OK.
4 In the previous step, I was able to selectively correct the perspec- tive for the architectural lines and the bicycle wheel. I deliberately left the bottom section (apart from the wheel) uncorrected to maintain the wide-angle distortion.
Finally, I made a selection of the bottom left and right areas and filled using the Content-Aware fill method.
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The Puppet Warp feature is avail- able from the Photoshop Edit menu and allows you to apply custom warps to images.
TIP
It is a good idea to convert the image to a Smart filter first be- fore you apply the Adaptive Wide Angle filter. This way you can go back and re-edit the settings at any time.
Adaptive Wide Angle filter controls
As you have seen in the two previous examples, the Adaptive Wide Angle filter can be very effective at selectively correcting the perspective. The initial dialog preview will vary depending on whether the underlying correction used is Auto, Perspective, or Fisheye. In most instances the Auto correction is automatically selected. Instead of applying a geometrically correct perspective correction, this applies a “shape conformal” projection, where the emphasis is on preserving the shapes in the image proportional to the distance from the viewer. To understand the key difference here, a lens profile correction in Lightroom, or the Lens Correction filter in Photoshop, will apply a correction where priority is given to obtaining the correct geometry at the expense of distortion in the way the image is projected. When using the Adaptive Wide Angle filter, priority is given to keeping the relationship between the elements in the scene in proportion, at the expense of being geometrically incorrect.
To use the Adaptive Wide Angle filter effectively, it is best not to apply a lens profile correction before you apply the Adaptive Wide Angle filter (especially if you are editing a fisheye lens image). A “shape conformal” projection is the starting point upon which you can add multiple constraints to determine which areas need to appear in “correct perspective.” As you add constraints, you are effectively overriding the initial, selected projection and adding a perspective type projection to that par- ticular section of the image.
The Adaptive Wide Angle filter works its magic by reading the camera body and lens EXIF metadata. It is then able to reference the lens profile database, allowing you to apply a geometrically correct perspective correction by adding constraints. As you do this it uses a Puppet Warp method to stretch or squash the pixels between the constraint lines. You can edit the constraints by clicking to select them and adjusting the endpoints. You can adjust the rotation as well, which can be useful if, say, you initially correct the lines of a building to make them vertical and then want to edit the lines to make the verticals converge slightly by a few degrees.
Photo merge corrections
The Adaptive Wide Angle filter is particularly good at correcting photo merge images, whether these have been created in Photoshop using the Photomerge feature or in Lightroom using the Photo Merge ➯ Panorama method. As with regular images, the filter reads in the lens profile data and takes into account the warping that occurs when the images are merged together. This means as you add constraint lines, the filter will know precisely how to follow the lines of curvature distortion to correct the curved edges and make them appear straight. The Adaptive Wide Angle filter can do a really good job of improving the look of panorama images that have been created using a photo merge technique.
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Correcting the perspective in a Photo Merge panorama
1 To create this Photo Merge panorama image, I began by selecting 10 single images in Lightroom and chose Photo ➯ Photo Merge ➯ Panorama (I explain this process in more detail in the following chapter). This produced the panorama image you can see here, where the images were all blended together smoothly, but the vertical and horizontal lines needed to be better aligned.
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2 I opened the image in Photoshop and applied the Adaptive Wide Angle filter. This defaulted to the Perspective mode, where I added the constraint lines shown here.
3 I was then able to edit the Focal Length setting to change the apparent lens focal length from 10.4 mm to 20.8 mm. This made the image appear less “wide angle.”
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4 After clicking OK to the Adaptive Wide Angle adjustments that were applied in Steps 3 and 4, I made a Magic Wand selection of the outer transparent areas. I then went to the Select menu and chose Modify ➯ Expand, where I expanded by 10 pixels. I followed this by choosing Edit ➯ Fill and applied a Content-Aware fill to the selected areas.
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5 I saved the image in Photoshop so that I could carry on editing it in Lightroom, where I applied a few Basic panel tone and color adjustments to improve the contrast and color saturation.
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