GIMP Fisheye Lens Simulation With Spherize Filter

The GEGL Spherize filter in GIMP is a distortion tool that maps an image onto a virtual sphere, accurately reproducing the optical curvature of an ultra-wide fisheye lens. This guide covers how to prepare your image layer, access the built-in GEGL Spherize filter, tune the distortion parameters for a realistic barrel effect, and optionally create a circular lens border.

1. Prepare Your Layer

  1. Open your image in GIMP by selecting File > Open.
  2. Right-click the active layer in the Layers panel and select Add Alpha Channel to ensure transparency support.
  3. If you want a non-destructive workflow, right-click the layer and choose Duplicate Layer to preserve your original image.

2. Open the Spherize Filter

  1. Navigate to the top menu and select Filters > Distorts > Spherize....
  2. A settings dialog will appear with an active real-time preview on your canvas. Ensure the Preview and Split view toggles are configured to your preference.

3. Adjust the Core Settings for a Fisheye Effect

To replicate the optical distortion of a physical fisheye lens, configure the following parameters:

  • Mode: Set this to Radial. Radial mode applies the distortion symmetrically in all directions from the center, which is necessary for a true camera lens simulation.
  • Curvature: Adjust the slider to a positive value. A positive curvature pushes the center outward toward the viewer, creating the characteristic "barrel" distortion of a fisheye lens. For subtle wide-angle effects, use a lower value (around 0.2 to 0.5). For extreme fisheye effects, push the value closer to 1.0.
  • Amount: Keep this set to 1.0 for the full effect of your curvature setting, or lower it slightly to blend the distortion with the flat original image.
  • Radius / Scaling: By default, the filter scales the effect to the edges of the active layer. Ensure the center coordinates (X and Y) are aligned with the optical center of your composition (typically 0.500 and 0.500).

Once the distortion looks natural, click OK to apply the filter.

4. Create an Optional Circular Fisheye Mask

True circular fisheye lenses produce a round image surrounded by a solid black circle. To simulate this:

  1. Select the Ellipse Select Tool (E) from the toolbox.
  2. In the Tool Options, check Fixed: Aspect Ratio and set it to 1:1.
  3. Draw a circle starting from the center outward across the main subject area.
  4. Invert the selection by going to Select > Invert (Ctrl + I or Cmd + I).
  5. Set your background color to black, create a new blank layer beneath your distorted image, and fill the outer inverted area with black using the Bucket Fill Tool or simply delete the excess area to transparent edges.