It’s commonly accepted that pictures never lie. Now, despite the obvious irony of printing that statement in a magazine about Photoshop, one of the truths about photography is that lenses don’t truly depict reality. Lenses are round, so light travelling through them bends with their curvature. This is most noticeable near the outside edge of images from wide-angled lenses. Architecture provides the best means of highlighting this skewed reality. Long, flat horizontal or vertical lines tend to bow when viewed through a lens. Edges of opposing colours might display a fringe of tones, or the corners of the image may appear darker due to a lens vignette. Each of these issues is the result of how the rounded camera lens broadcasts light onto a flat image. However, the manner in which these issues are created can be calculated and predicted.
Work with auto correction
Step 01: Begin with auto correction
Retrieve the ‘Cathedral.jpg’ image supplied online at http://blog.advancedphotoshop.co.uk/tutorial-files. Go to Filter>Lens Correction and in the Auto Correction tab ensure that the Lens Profiles box is populated with at least one lens profile. In the Correction area check the Geometric Distortion and Chromatic Abberation checkboxes, but leave the Vignette box. Engage the Auto Scale Image box and set the Edge to Transparency. To see the effect of the lens correction toggle the Preview checkbox.
Step 02: Manual adjustments
Switch to the Custom tab for additional adjustments to set by hand. Begin with the Transform area, setting the Vertical Perspective to -40. This removes the exaggerated vertical perspective in the image. To compensate for some of the other distortions introduced, set the top Remove Distortion slider to -2. Then set the Vignette amount to -45 for a more artistic appearance. These corrections will push the top of the structure out of frame. To recover it, reduce the Scale to 93%.
Step 03: Corner treatment
Click OK and Photoshop applies the correction. To address the hole at the bottom of the image, first create a selection of the layer by Cmd/Ctrl-clicking on the layer thumbnail. Invert the selection, then go to Edit>Fill and set the Use to Content-Aware. Photoshop fills in the hole with resampled pixels from the rest of the image. Hit Cmd/Ctrl+D to cancel the selection. If there are further visible lens distortion issues, you can run the Lens Correction filter again to refine further.