Gimp Tips - Bloom

Bloom is an effect light has on film where light appears to blur in around the edges when you have a dark object in front of a light background. Many photographers avoid such a juxtaposition for just this reason, but others use it purposely to gain a certain stylized look. The film Sky Captain and the World of Tomorrow used bloom extensively in building their unique look. Here is how you can add some fake bloom to a picture with a dark object against a light background.

  1. My beautiful wife with cloud in the background Here again to help out is my beautiful wife, Libby (photo by Tim Howley). The original photo didn't have the light background needed to illustrate this technique well so I filled it in with these clouds to lighten it up a bit.
  2. Channels area with Libby pasted into the new channel Begin by selecting the whole image, and copying it. Make a new channel and past the image into it. This will automatically grayscale it, since channels can't have color.
  3. The Libby channel is now darkened With the channel still selected go into Colors|Curves and move the bottom corner over to (128,0). This will darken the image in the channel and sharpen the contrast, emphasizing the light areas of the image (that we want to bleed into the darker ones).
  4. Libby image with a strange selection area around the bright things Turn the channel you created into a selection and grow it by about 10 (the amount you grow it affects how deep the bloom penetrates into the dark areas of the image).
  5. Libby with strange white patches colored over her Add a new transparent layer. Using the bucket tool, fill the selected area with white.
  6. Now the white patches have been smoothed out by blurring them Select|None then Filters|Blur|Gaussian Blur by about twice as much as you grew the selection (so in this case 20).
  7. Libby with the final bloom effect applied Finally, turn down the opacity of that white layer to affect the degree of the bloom. I used 40%.