UNDERSTANDING COLOR

Computer monitors produce millions of colors by mixing varying levels of red, green, and blue light.  These three are complemented by opposite colors of cyan, magenta, and yellow.  Color correction software provide controls to add/subtract colors, including Curves, Levels, and White/Color Balance.  Generally a combination of two colors will need to be altered.  It is better to make several small adjustments if coarse adjustments don't work well.  Always try using automated corrections before resorting to manual ones.  Programs such as Photoshop allow you to fade the current adjustment.  I find that a combination of Auto Levels and Auto Color, along with fading produces good results with the least amount of effort.   

What is interesting about color correction is that there are two ways to make the same adjustment.  For example, an image with too much green can be easily corrected by subtracting green, moving the slider toward magenta, but the same effect can be accomplished by adding equal amounts of red and blue.

Silkypix RAW conversion software approaches color correction in a different way, with a primary Blue to Red slider and two Green to Magenta sliders, one for highlights and the other for shadows.  This method takes practice to master.

Color spaces are data tables created in an effort to reproduce colors accurately between various devices such as cameras, computers, and printers.  Two common photographic color spaces are sRGB and Adobe RGB.  The sRGB color space has a limited color palette barely acceptable for posting images to the web, not printing.  Serious photographers should use the Adobe RGB color space since it has a wider color palette which renders colors more naturally on screen and print.  In order to see the difference one must be using a high-quality monitor.

Inexpensive monitors are designed for web browsing, games, and office work using the sRGB color palette which reproduces much less than what the eye can distinguish.  High quality photo editing monitors designed to reproduce the Adobe RGB palette cost several times more but are worth the investment if you are serious about photography.  Regardless of the make/model a monitor should be calibrated before editing.

Monitor calibration is extremely important for digital photographers.  Unless your monitor is calibrated the colors on your camera, computer, and prints will not match.  Color corrections and adjustments using software will not be accurate or easy.  A variety of calibration devices are available, some for less than $100.  I use a ColorVision Spyder and the difference is immediately apparent when I look at images corrected before and after.

Quality digital cameras are usually quite good at producing acceptable colors, however underwater performance can be hit or miss depending upon a few factors.  Regardless of the cause, a fair number of images can be corrected with imaging manipulation software regardless of brand.  Best results are obtained from high-end programs including Photoshop and Paint Shop Pro but simple 'one-click' solutions from Picasa and those bundled with your camera may produce remarkable results.  These corrections will work with any digital image format but the best results can only be realized by users whose cameras offer RAW image capture.

Some cameras have an 'Underwater' scene mode that adds orange to the image to offset blue light.  This is akin to placing an orange filter on a film or video camera minus exposure adjustment caused by the filter itself.  Despite this option the best practice is to set the camera's white balance to 'Daylight' or 'Auto WB' if it produces satisfactory results.

Of course you could take photos at depth using available light employing a 'Custom' white balance (see your camera manual) but my experience with this method is that it is best reserved for wide angle/available light scenes.  Custom white balance must also be reset with major depth changes or alternating sun/clouds.  Closeup work requires the additional depth of field & sharpness possible with flash.  Custom white balance should not be used underwater along with flash.

Available light using Custom white balance

Note unsharpness due to subject movement & lack of flash

Auto white balance plus flash

Improved sharpness provided by flash

SATURATION

Sometimes color correction alone can appear artificial, especially when the image is richly colored or over-saturated.  Most Point & Shoot cameras lean toward over-saturation.  The intensity of color can often be reduced to restore a more natural look.  Signs of over-saturation are most noticeable in the image's highlights and shadows.  If your software has the option of adjusting saturation by individual color you can simply de-saturate that channel.  Another method is to use the Levels or Histogram tool to adjust the unwanted color's highlights and shadows. 

 INCREMENTAL ADJUSTMENTS

The most common color issue is caused by cyan/blue ambient light from filtered sunlight.  Adding red and/or yellow (orange) can help things look more true-to-life.  I suggest making several incremental changes rather than a big one.  The best way to recognize how much incremental adjustment is 'enough' is to keep the image highlights from assuming the colors you are 'adding'; i.e. keep the whites white.  By making several small adjustments you should be able to obtain a more pleasing and natural-looking product while adding more orange overall.

Uncorrected

and

reduced saturation