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Gradient elimination

✅ Photoshop


GradientXTerminator is a gradient removal plug-in for Photoshop and Affinity Photo that is fast and easy to use. It can process 32-bit, 16-bit, or 8-bit images, grayscale or RGB color. It easily tackles large-scale gradients from light pollution, but can also handle vignetting and even tricky edge, corner, and circular gradients that are very hard to deal with otherwise. And assuming you already use Photoshop in your work flow, you may now have one less program to transfer your image into.

Gradients, whether caused by light pollution or image calibration errors, have always been a problem with amateur astronomical imaging. In the past, image processing programs have tried to correct gradients by automatically determining how they affected an image. This was usually detrimental, since the software could not easily differentiate between background areas and actual objects. A bright galaxy in the center of an image, for example, would “fool” the software, resulting in a dark halo around the galaxy.

More recently, tools have become available that allow the user to tell the software what parts of the image are background by placing small markers on the image. This was a great leap forward and produced much improved results. But for complex gradients that arise from multiple stray light sources and flat-field calibration errors, these tools are less than convenient. They can sometimes be made to work, but tens or even hundreds of background points must be marked for the tool to build an adequate mathematical model of the gradients.

For more details, check out the GradientXTerminator tutorials and manual.

System Requirements

✅  Photoshop
✅ Affinity Photo
❌ PixInsight

  • Windows 10 or later
  • MacOS 10.15 (Catalina) or later
  • Photoshop CS4 or later (64-bit only)
  • Affinity Photo 2.1.1 or later
    • Earlier versions of Affinity Photo have a bug that prevents the background selection from being properly communicated to GradientXTerminator. This was fixed in Affinity Photo version 2.1.1.

Revision History

Version Date Comments
1.6.0 7 May 2023 Enabled 32-bit image processing for Affinity Photo 2.
1.5.0 25 Nov 2022 Updated the MacOS and Windows installers to add installation for Affinity Photo 2. No changes to the plugin.
1.5.0 16 May 2021 (Mac-only update) Apple M1 silicon Mac compatibility.
1.4.1 16 Sep 2020 Affinity Photo compatibility. Settings, including license information, are now saved in a manner that is compatible with both Photoshop and Affinity Photo. The Mac version is now also signed with an Apple Developer ID and notarized by Apple, eliminating security warnings on MacOS Catalina and later.
1.3.0 5 Dec 2010 Ported plug-in to work in 64-bit mode with Photoshop CS5 on Mac OS X 10.6 (Snow Leopard).
1.2.0 29 Nov 2008 Ported plug-in to work on 64-bit Windows Photoshop installations (XP 64 or Vista 64). Fixed the “strength” parameter reversal on the Mac version.
1.1.4 15 Nov 2008 Fixed a registration bug.
1.1.3 1 June 2008 Made registration email address case-insensitive.
1.1.2 10 May 2008 Changed registration reminder (nag screen) to only show up once per day.
1.1.1 21 April 2008 Fixed registration issue on PowerPC-based Macs.
1.1 20 April 2008 Ported plug-in to work on both Windows and Macintosh computers. Revised licensing system to be more robust (permanent keys will not require re-entry.)
1.01 23 April 2005 Maintenance release:

  1. Now works correctly on layered images.
  2. Disabled the plug-in for images in modes other than RGB and
    (Please convert other images to one of these modes to use the plug-in.)
  3. Now gracefully handles the situation of not having enough background area selected to extract gradient information.
1.00 12 April 2005 Initial Release