Getting the most out of your underwater photographs

We've all been there ... at least those of us who are stupid enough to drag cameras with us while we go scuba diving ... You get back from the dive, and you look at the pictures you took and you find there's that one picture that looks good ... except for that blue/green cast dominating subject and background. It looks flat and you remember thinking how beautiful and colorful the fish was when you took its picture.

What can you do? Well ... here's a method that can often return significant natural-looking color to your underwater images that have that blue/green cast. This technique works best with images without a lot of water column and lots of colorful stuff. I'm using Photoshop CS3 for this tutorial, but most of the effects are easy to replicate in other editors.

Here goes ... the image I'll be starting with was generously permissioned by fellow underwater photographer David Sifre - Thanks David! (David's blog can be found at http://divelove.wordpress.com/).

Step one ... Surprise! This step has nothing to do with color and more to do with Sharpening. I find that many underwater photographs with lots of nice textures and details can benefit from a bit of local contrast enhancement and fine sharpening that one can achieve with the application of an unsharp mask or masks.

This filter tool can be found under Filters>Sharpen>Unsharp mask. I use an amount of somewhere between 110 and 150 and a radius of 0.6-0.9 with a threshold of zero. Sometimes I follow this up with a second pass with another unsharp mask with the amount down to 20-25 and the radius up to 30-50 and the threshold somewhere between 8-12.
Don't be afraid to dial it back and make sure to preview the results in a 1:1 magnification to truly see the impact ... you don't want to oversharpen the image, but done right you can really accentuate the details of an image this way.



Ok ... Step 2 ... on to the color part.

Make a duplicate layer from your background. You can do this by right-clicking the layer in the layer control or on the toolbar under Layer>Duplicate Layer ... Next, use a Blur filter (average is best) to completely schmear the layer into a solid color field. It will likely look something like this:

Next, hit CONTROL and "I". This will invert the color field layer and should look like this:

Now look at the layer control ... each layer has pull down option that defaults to "Normal" next to another control labeled "Opacity" with a value of 100% ... the first pulldown contains the blending options for this layer. Switch this from "Normal" to "Overlay" and play with the opacity until you think the image looks good.

Lastly, I often will hit an image like this with an "auto-level" adjustment. If you want to preserve the maximum flexibility and use non-destructive techniques, you can create a levels adjustment layer and apply the auto-level that way. That can be found under Layer>New Adjustment Level>Levels ... Or, if you are happy to start the process of collapsing the image to a single output file, you can "flatten" the color layer and the background into a single layer by going to Layer>Flatten Image at which point you can apply an auto-level adjustment directly to that single layer with Image>Adjustments>Auto-level.

Here's the final result ...

EDIT...

This post was referenced on the front page of Wetpixel.com, a site dedicated to underwater photography. Here's a link to that article from Wetpixel.

http://wetpixel.com/i.php/full/jeremy-payne-on-underwater-color-correction/

Thursday, July 31, 2008
Jeremy Payne on underwater color correction

Wetpixel member Jeremy Payne posts a link to his technique for color correcting underwater images exposed with too little strobe light.
Here’s a method that can often return significant natural-looking color to your underwater images that have that blue/green cast. This technique works best with images without a lot of water column and lots of colorful stuff. I’m using Photoshop CS3 for this tutorial, but most of the effects are easy to replicate in other editors.

Posted: Eric Cheng 07.31.08 04:14 AM
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