Tech

How to Correct Wide-Angle Stretch

September 2020 issue

How to Correct Wide-Angle Stretch

If you’re using lenses 24mm or wider, you’ve likely noticed unnatural effects at the edges of your images. This is especially apparent when a lack of space forces you to use a wide-angle lens for a group photo or wedding party. These abberations exist even after applying lens corrections in editing software because they’re not the result of optical lens distortions but due to an effect called anamorphosis or, more commonly, volume deformation.

Volume deformation arises because a three-dimensional object cannot be exactly mapped onto a two-dimensional plane, such as an image sensor. Previously this effect could be corrected only with the use of ViewPoint from DxO Labs. With the release of the Nik Collection 3 plug-in from DxO, you can now correct volume deformation in Adobe Photoshop, Photoshop Lightroom, Photoshop Elements, and DxO PhotoLab.

For this tutorial, I used Perspective Efex in Photoshop and Lightroom on Windows and iOS systems.

HOW TO TAME DEFORMATION

Apply the volume deformation correction by selecting Perspective Efex in the Nik Selective Tool 2 toolbar in Photoshop or by selecting Photo > Perspective Efex > Edit in Lightroom.

Depending on how the image is deformed, Perspective Efex provides two methods of correction: horizontal/vertical and diagonal. If heads or objects near the edge of the frame appear stretched or flattened, then first try the horizontal/vertical icon. It’s located to the left in the Volume deformation subpanel. When you select it, the image is processed with a default horizontal correction based on EXIF information in the digital image file. Two sliders are provided for fine tuning the correction both horizontally and vertically. These are most useful to reduce some of the correction if the original image becomes too cropped to show all of the relevant content.

When the image stretches to the corner of the frame (left) applying the default diagonal adjustment corrects the volume deformation (right).
© Stan Sholik
When the image stretches to the corner of the frame (left) applying the default diagonal adjustment corrects the volume deformation (right).
The diagonal adjustment tool icon is located to the right of the horizontal/vertical icon in the Perspective Efex workspace.
© Stan Sholik
The diagonal adjustment tool icon is located to the right of the horizontal/vertical icon in the Perspective Efex workspace.


Another adjustment in the submenu corrects volume deformation when the objects stretch to the corners of the image rather than to the sides. Again, a default correction is applied based on EXIF data and a single slider is available for fine tuning.

I found that group photos made with the camera generally level required the horizontal/vertical correction, and captures showing more dramatic perspective called for the diagonal correction. You can easily try them both and then decide which gives the better adjustment. In order to correct for volume deformation, some cropping of the image area occurs. Keep that in mind when you make your capture and as you apply the adjustment.

With some images it is difficult to decide whether a horizontal/vertical or diagonal adjustment is more appropriate (left). In this case the diagonal
adjustment worked better (right).
© Stan Sholik
With some images it is difficult to decide whether a horizontal/vertical or diagonal adjustment is more appropriate (left). In this case the diagonal adjustment worked better (right).


With diagonal adjustments, the image is not only cropped, but lines become curved. This is most obvious when there are strong horizontal lines in the image, but it’s also visible in the repeating patterns that can be found on floors. Even when the diagonal adjustment provides the better correction, you may decide the horizontal/vertical adjustment looks better overall if curving is too noticeable.

Volume deformation is only one subpanel of the new Perspective Efex tab in Nik Collection 3. The unique ability of this plug-in to correct a common issue quickly makes it worthy of a closer look. Other sections of Perspective Efex correct horizontal and vertical lines, tilting buildings, and even flatten full-frame fisheye images.

The new Perspective Efex module is one of the eight plug-ins in Nik Collection 3. The collection retails for $149, and upgrades are $79. A 30-day trial of Nik Collection 3 by DxO is available.  

Stan Sholik is a writer and photographer in San Clemente, California.

Tags: lightroomphotoshoppost capturetutorial

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