Image processing for Digital Underwater Photos

This article describes a number of simple methods of improving your digital underwater photos using your PC, as well as a number of tips to maintain a high level of quality in both image files and prints.

[Original photo]

Software

Editing photos does of course require capable image processing software. Adobe Photoshop is the well-know number 1 in the graphical sector, but the high price makes this package less interesting for the home user. Cheaper alternatives are abundant, with suites like Photoshop Elements, Corel PhotoPaint, Jasc Paintshop Pro, Microsoft Photo Standard and Linux' GIMP. All of these programs provide sufficient tools and options to perform the basic modifications shown below to enhance underwater photos.

Color correction

As you have learned as diver, red is the first color to disappear under water. The resulting blue/greenish results can be corrected for this loss by increasing the redness of the photo and adjusting the other. Imaging software has got special functions to achieve this: Curves, Color Balance, Hue and White balance are the most common. Applying these functions on the example photo already reduces the blue haze and make the seal and kelp come out better.

[Color correction]

If possible, only select the Red channel when using these functions and experiment until the photo shows the desired results. When you are not satisfied with the results, try starting over by taking the original file again to prevent correction on correction. Also be modest in applying the color filters: in the end blue is the color the viewers associate with the underwater world.

Exposure Correction

Photos that are too dark or too light can be corrected using the Brightness/Contrast function. The effects of this tool can become too obvious very quickly, so use it only limited. Applying a slight reduction in brightness and a minor increase of contrast is sufficient give it a much softer and better balanced appearance.

[Exposure correction]

The Gamma and Curves tools can also be used to obtain a certain degree of exposure correction. Do select all color layers (RGB: Red, Green, Blue) to obtain a well balanced result.

Selection

Previous modifications have all been applied to the whole image at once, many photos do however only have a specific subject or area that require modification. Special selection functions like the Lasso, Magic Wand and Free Hand aid you in marking out these areas for separate editing. You can then use the same functions for color and exposure correction until the desired effects for the selection is achieved.

[Modifying a selection]

All previous corrections for example still left too much emphasis on the kelp. But by selecting the seal, and applying color and exposure correction separately the seal stands out more just as it is supposed to do.

The Result

As has been shown, a small set of simple functions is sufficient to improve digital underwater photos tremendously.

The end result on your photos does of course still depend on the quality of and information in the original photo, but it is always worth trying to get the most out of it.

[The result]

Printing

Traditional photography uses a 2:3 ratio for image sizes, like the common 10 x 15 cm print format. Your digital photos use a ratio of 3:4, like the 1536 x 2048 pixels results of 3 megapixel cameras. To get these printed without distortion, a Photo Lab will leave out part of the upper and lower image when exposing the photo, resulting in a significant loss of the image area.

[2:3 area]

To prevent this loss you can crop your photos to the 2:3 ratio your self. Also many interactive printing machines and web sites offer functionality to set the print area for each photo upon request. Special digital 3:4 print formats, like 11,4 x 15 cm, are also becoming available, but do keep in mind that most photo books, holders, frames etc. are not yet designed for these formats.

Also read: Using RAW instead of JPG and underwater color correction.

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