Apply a vignetting effect to the image.
Vignetting is a modification of the brightness and saturation at the borders of the image in a specified shape. Many of the parameters listed below can also be modified with a graphical control that overlays the image when the module has focus, showing the shape and extent of the effect.
Note: This module is known to provoke banding artifacts under certain conditions. You should consider activating the dithering module to alleviate this.
Also note: This module can produce unnatural-looking results and should be used with care. Instead, use the exposure module with an elliptical mask with a large transition area and, if necessary, use the color balance rgb module with the same mask to reduce saturation at the edges.
- The radius of the vignetting area.
- fall-off strength
- The progressiveness of the fall-off. Lower values cause a steeper transition.
- The intensity of brightening (positive values) or darkening (negative values).
- Control how strong colors become when desaturated/saturated in the darkened/brightened vignetting area.
- horizontal/vertical center
- Shift the center of the vignetting area horizontally/vertically.
- The shape of the vignetting effect. The default value of 1 creates a circular or elliptical area. Smaller values shift the shape to being more square; higher values turn it into a cross-like shape.
- automatic ratio
- Automatically adjust the width/height ratio of the vignetting area to match the aspect ratio of the underlying image. This typically causes the vignetting area to become elliptical.
- width/height ratio
- Manually adjust the width/height ratio of the vignetting area.
- Activate random noise dithering to alleviate banding artifacts caused by vignette gradients. Select “8-bit output” to prevent banding on monitor display and for JPEGs. When set to “16-bit output”, only a small amount of dithering is applied, just strong enough to compensate for banding on the fine grained 16-bit level. It is now recommended that you instead use the dithering module to alleviate banding artifacts.