Negative Difference Processing

A method of albedo enhancement of gray scale lunar images

The following is a simple method for the enhancement of fine gradational differences in monochrome lunar images using Photoshop. The method is very quick to apply and enhances both albedo changes and fine scale surface detail.

Load a starting image that's already been fully processed for best normal presentation such as the following shot of the Kepler/Aristarchus region under high sun angle:

 Create a duplicate layer using the default values. Go to "Image, Adjust" and click on "Invert". This will create a standard negative image over the original positive image:

While keeping opacity at 100% change the layer combine method to "Difference" to get the following result:

At this point you can flatten the image and adjust the levels as needed to bring out the maximum amount of detail in all areas. The overall effect  of all this is rather dramatic, subtle albedo changes are much easier to trace, especially in the rays that now stand out in bold tonal relief. Sharp features are also very much enhanced enhanced, note the appearance of Valles Schroter and the very finely etched line of Rima Marius as it winds through the area between Aristarchus and Marius.

Here's another example of the tonally varied area surrounding Rima Hyginus:

Tony Gondola, November 2005