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Background Repair w/ PhotoShop


Sometimes we get an image with a problematic background. The following process is not for the faint of heart purest. However, there are times when we may want to simply replace the entire background with an artificial one. As a last gasp effort, this can save an image that is doomed for the Recycle Bin.


Image 1

Image 1 is our starting point. The image has a noisy, uneven background, but also shows some faint galaxies. The following steps will make the background smoother with little or no loss of faint galaxies.


Figure 2

  • Load your image into PhotoShop.

  • Use the Eyedropper to select the background color.

  • Use Ctrl-A, Ctrl-C to copy the image to the clipboard.

  • Use File|New to create a new image. I have PhotoShop set to automatically use the image, on the clipboard, for setting the height and width.

  • Select and set the Paint Bucket Tool (PBT) opacity to 100% and the Tolerance to zero. Now use the PBT to paint the image with the previously selected background color.

  • Image 2 shows the new artificial background


Image 3

The problem with the new background is that it is perfectly smooth.  So, it is necessary to add some noise to make it look natural. However, the added noise will be at a lower level than the original image.

Use the Noise Tool, as shown in Image 3, to add noise to the artificial background. Try levels from about 1.5 to 2.5. Also, try experimenting with the Uniform or Gaussian distribution. Sometimes it is useful to uncheck Monochromatic and use a background with random color noise.


Image 4

Now we will add our new background to the original image, see Image 4.

  • Use Ctrl-A, Ctrl-C to copy the new background to the clipboard.

  • Select the original image and use Ctrl-V to paste in the contents of the clipboard, as a new layer.

  • Set the blend mode for layer one to Lighten.


Image 5


Now, in Image 4, we have a perfectly flat low noise background. However, it is too bright and a covers the faint galaxies. Adjusting the brightness of Layer 1 repairs this.

Simply use the Brightness/Contrast tool to adjust the brightness so that the faint background galaxies start to disappear. With careful adjustment it should be possible improve the background with little or no loss of faint detail... see Image 5.

Finally, flatten the image. Roll the mouse in an out of Image 5 to see the before and after result.