4.8. Lens Distortion
| 4. Distort Filters |

### 4.8. Lens Distortion

#### 4.8.1. Overview

Figure 16.48. Example for the “Lens Distortion” filter

Original image

“Lens Distortion” applied

This filter lets you simulate but also correct the typical distortion effect introduced in photo images by the glasses contained in the camera lenses.

#### 4.8.2. Activating the filter

This filter is found in the image window menu under Filters → Distorts → Lens Distortion.

#### 4.8.3. Options

Figure 16.49. “Lens Distortion” options

The allowed range of all options is from -100.0 to 100.0.

Preview

  The result of your settings will appear in the Preview without affecting the image until you click on OK.

Main

  The amount of spherical correction to introduce. Positive values make the image convex while negative ones make it concave. The whole effect is similar to wrapping the image inside or outside a sphere.

  Figure 16.50. Example result of Main option

  -100.0

  0.0

  +100.0

Edge

  Specifies the amount of additional spherical correction at image edges.

  Figure 16.51. Example result of Edge option (Main set to 50.0)

  -60.0

  0.0

  +60.0

Zoom

  Specifies the amount of the image enlargement or reduction caused by the hypothetical lens.

  Figure 16.52. Example result of Zoom option

  -100.0

  0.0

  +100.0

Brighten

  The amount of the “vignetting” effect: the brightness decrease/increase due to the lens curvature that produces a different light absorption.

  The Main or Edge options must be non zero for this option to produce noticeable results.

  Figure 16.53. Example result of Brigthen option (Main set to 75.0)

  -25.0

  0.0

  +25.0

X shift; Y shift

  These two options specify the shift of the image produced by not perfectly centered pairs of lenses.

  As above this option produces visible results only if the Main or Edge options are non zero.

  Figure 16.54. Example result of X shift option (Main set to 70.0)

  -100.0

  0.0

  +100.0

4.7. IWarp |  | 4.9. Mosaic