GradientXTerminator is a gradient removal plug-in for
the Windows version of Adobe Photoshop® that is
fast, easy to use, and really works. It can process 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.
Enter GradientXTerminator. Three key features make this
a superior tool:
- Simple, intuitive user interface.
processing tools sometimes seem like they were written by computer programmers for computer
programmers. Obscure numerical parameters, excessive numbers of
settings, and clunky user interfaces are a barrier between you and the
results you want. With GradientXTerminator, you don't have to be a
mathematician to make it work.
- Familiar background selection methods.
probably already use Adobe Photoshop®
to do the final processing steps on your images. You are probably
already familiar with its rich set of selection tools, such as the
Lasso, Magic Wand, and Color Range tools. Rather than forcing you to
click many times to place background markers, GradientXTerminator allows
you to use the tools you already know to tell it where the background
- Sophisticated mathematics.
Behind the friendly and comprehensible user interface is an advanced
mathematical modeling engine. The hardest part of correcting a
gradient, even when a tool is told where the background is, is what
to do in the rest of the image. GradientXTerminator finds the
optimal model of the gradient based on the input you give it.