Everyone who takes digital photos without a powerful strobe or a red filter will have taken shots that look like the 1st image on the right. 

This is the effect of light travelling through water. In fresh water, light generally loses most of it’s red and some blue leaving images greenish. In salt water, light loses most of it’s red and some green, resulting in images that look very blue.

 

Most computer users familiar with image processing software will immediately reach for the “levels” feature in their favourite application (this article refers to Adobe Photoshop). However, when you attempt to pull the level sliders, something strange happens - you get an image that looks like the 2nd image. This is because the original image contains little or no “red” data and what's there has had it’s levels increased to cover the image’s whole dynamic range.

 

Even if you manually adjust the level sliders yourself, you can at best only achieve results like the 3rd image. There’s just not enough “information” in the picture to create a properly colour-balanced image.

 

So what do you do? Well you can manufacture the missing “red” data from the luminosity (brightness) data of the other 2 channels (green and blue). This will result in an simage similar to the last one on the right.

 

The process is as follows:

  1. Load your image into any version of Adobe Photoshop.

  2. Create 3 duplicate layers of the original photo (Layer > Duplicate Layer > OK)

  3. Make the middle duplicate layer active (second one down in the ‘Layers’ palette) by single clicking on it in the ‘Layers’ palette (palette with Layers-Channels- Paths)

  4. Fill that layer with 50% grey (Edit > Fill > 50% Gray, 100% opacity, normal)

  5. Make the top duplicate layer active by single clicking on it in the ‘Layers’ palette. Change that layers blending mode to ‘Luminosity’ (Layer > Layer Style > Blending Options > Blend Mode > Luminosity) Merge that layer down into the middle grey layer. (Layer > Merge Down). You now have a B&W image of your original photo in this layer.

  6. Create a new fill layer above this B&W image (Layer > New Fill Layer > Solid Colour). make sure ‘Group with Previous Layer’ is ticked. Fill this layer with red (R: 255, G: 0, B: 0). Change this layer’s blending mode to ‘Multiply’ (Layer > Layer Style > Blending Options > Blend Mode > Multiply) and merge it down into the previous layer (the B&W image) (Layer > Merge Down). You’ve now have a red photo.

  7. Change the blending mode of the red photo to ‘Screen’ (Layer > Layer Style > Blending Options > Blend Mode > Screen) and merge it down into the first duplicate layer (Layer > Merge Down). You’ve now got your original image with a set of artificially created red data.

  8. Run Auto-Levels (Image > Adjustments > Auto Levels). See how you like the results. If not, undo them (Edit > Undo Auto Levels) and adjust the ‘Levels’, ‘Contrast’ and ‘Brightness’ manually.

  9. Make adjustments with the Hue/Saturation (Image > Adjust > Hue/Saturation) and Colour Balance (Image > Adjust > Colour Balance) until you get the desired effect.

  10. Adjust the sharpness (Filter > Sharpen > Unsharp Mask). A window will open with an automatic percentage adjustment shown. Increase or decrease the adjustment if you’re not satisfied with the results.

  11. When you’re finished, flatten the layers (Layer > Flatten Image), re-size the image to your requirements and save the photo as a new file. Never overwrite your original photo as you may want to do something else with it in the future.

Top Tip

You can automate this process by creating a Photoshop "Action" which can be stored in a library of requently used operations.

 

Running an action on a photo takes a fraction of the time compared to performing the steps manually.

 


Original image - very blue with virtually no red data


Poor results after using auto "per channel" levels


Best attempt to manually adjust "per channel" levels. Still no real improvement


Much better results after adding artifical red data