Sometimes an RGB color or monochrome image contains too much information to make the image usable. A negative image can address this by making the black space white, and the light areas dark thereby highlighting parts of the image that might not have been visible before.

This article walks you through installing and using a Photopea.com set of actions to create a negative black and white image.

Result

This is an image of asteroid 6478 Gault that was taken on February 11, 2019, between 03:05UT and 03:42UT. The image has been aligned on the asteroid, so you see star trails in the image:

The image is good in that it reveals the two tails of the asteroid, however, more detail can be recovered from this image. This is a negative black and white image showing much more detail in the asteroid:

In this image, the second tail above the longer one is more apparent – this was completely invisible in the preceding original image.

Loading The Actions Into Photopea

Photopea.com makes it possible to record a set of actions that can be played back at a later time, saving you from having to remember menu selections.

I include a simple set of actions that generate the negative image for you and once you have that, you can further adjust to bring out more detail as I have here.

1. Download this file: RemoteAstrophotography-com-NegativeBW-Action.zip

2. Open the file in Photopea – select File – Open and locate the file

3. Photopea will ask if you want to load this file each time you start Photopea – select Ok

4. From the menu, select Window – Actions to bring up the Actions window

Execute the Negative Action

1. Open an image in Photopea.com (select File – Open)

2. From the menu, select Window – Actions

3. Select the Negative action

4. Click Apply at the bottom of the window

The image will become a negative of the original.

You can bring out more detail in the image by performing a Curves adjustment similar to the following:

Implementation of Action

If you’re not using Photopea and want to do this yourself in Photoshop or GIMP, here are the steps that the action implements (you can adapt these steps to your photo editor):

  1. Invert the image
  2. Desaturate the image
  3. Apply a curves adjustment to highlight the upper-end of the histogram

Conclusion

Creating a negative image is a useful process whereby you can recover information from an image that’s not apparent in the original image. This article showed you how to generate a negative image and then adjust it to bring out more details in it.