Adobe Photoshop CS5 for Photographers - Martin Evening [237]
Edge pixels
As you apply Lens Correction Transform adjustments, the shape of the image may change. This leaves the problem of how to render the outer pixels. The default setting uses the Transparency mode, although you can choose to apply a black or white background. Alternatively you can choose the Edge Extension mode to extend the edge pixels. This may be fine with skies or flat color backdrops, but is otherwise quite ugly and distracting, although the extended pixels may make it easier to apply the healing brush in these areas.
You can adjust the rotation of an image in a number of ways. You can click and drag directly in the Angle dial, but I mostly recommend clicking in the Angle field (circled in Figure 10.10) and using the up and down keyboard arrow keys to nudge the rotation in either direction by small increments. The other option is to select the rotate tool and drag to define what should be a correct horizontal or vertical line. The image will then rotate to align correctly.
The Scale slider can be used to crop a picture as you apply a correction. On the other hand you may wish to reduce the scale in order to preserve more of the original image (as shown in Figure 10.10). The Show/hide Grid overlay can prove useful for helping you judge the alignment of the image and you can also use the move grid tool to shift the placement of the grid. The grid controls at the bottom of the Lens Correction filter dialog also enable you to change the grid color and dynamically adjust the grid spacing, plus toggle showing or hiding the grid.
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In this example I checked all the Auto Correction options to apply an auto lens correction to this photograph, which in this case was based on the EXIF metadata contained in the original photo (there is a layered version of this image on the DVD for you to compare).
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I then switched to the Custom mode and applied a custom lens correction to further correct for the perspective angle this photograph was shot from. Basically, I adjusted the Vertical and Horizontal perspective sliders and made a minor adjustment to the angle of rotation. You'll also note that I adjusted the Scale slider to zoom out in order to preserve the sky at the top of the photograph.
Selecting the most appropriate profiles
If the camera/lens combination you are using matches one of the Adobe lens correction profiles that was installed with Photoshop CS5, then that is the only option You'll see appear in Lens Profiles (Figure 10.11). If no lens correction profile is available (because the necessary lens EXIF metadata is missing), You'll see a ‘No matching lens profiles found’ message. The Search Criteria Camera Make, Camera Model and Lens Model menus will then allow you to manually search for a compatible camera/lens profile combination. If you wish to explore some alternative lens profile options, then click on the ‘Search Online’ button. This carries out an on-line search for lens correction profiles that have been created by other users where the lens profile EXIF data matches and the profiles are publicly available to share. You can initially preview these profiles to see what the results look like before deciding whether to use them and save them locally to your computer. If you create your own custom profiles, as shown on pages 564–565, and wish to share these with other users, you can do so by going to the File menu and choose ‘Send Profiles to Adobe…’ ( ) (Figure 10.12). If you can't find any matching lens profiles then you can always select the nearest equivalent via the Search Criteria menus, and fine-tune the result using the Custom panel controls in the Lens Correction filter dialog.
Figure 10.11 You can choose to prefer raw profiles via the Search Criteria section fly-out menu options in the Lens Correction filter dialog.
Figure 10.12 The Send Profiles to Adobe dialog.
The Lens Correction filter can make use of profiles that have been created from raw files or from rendered TIFF or JPEG capture images. This means that two