I've done one Photoshop feature article here, about using Apply Image to repair damaged color channels, specifically to correct or salvage) u/w images in which the red channel is badly damaged or non-existent, which can easily occur with images illuminated purely by ambient light at depths of 20 meters or more, particularly subjects which might be shot at distances beyond strobe range such as pelagics and wrecks.
Learning PS looks like it might turn into a life-long thing. I keep discovering "new" tools and techniques that really do make me want to throw it all away and redo almost every image I've ever done. Unfortunately, ars longa, vita brevis.
For me, the latest discovery has been magic wand/lasso or color match tools to select the background water, feathering, and then selectively applying noise filters to those areas (or, alternatively, selectively not applying full sharpening to background areas, which sometimes amounts to almost the same thing). This allows more sharpening on the main subject without kicking the noise in the background up so high that it starts to look like woven fabric.
I'm sure this is something knowledgeable PS users would consider very basic, but I hadn't worked out a good way of doing it before. So it's taken me, what, five years to figure out that I really don't need to apply sharpening to the background water (or sky, or out-of-focus areas in a macro shot).
Using layers with variable opacity and/or different modes to fine-tune the effects of global changes is something I'm more likely to bother with now than before. The history brush is another tool that I'm just starting to get a handle on.
Some here may argue that discussions like this belong on a different website, one focused on photoshop techniques, and they would have a point. Personally, I think that many problems of underwater images (and the best techniques to solve them) are specific enough to more than justify having those discussions here. Dealing with wiped out red channels on images taken with ambient light in deep water is just one example.
That's why I'm glad one forum on this site is dedicated to "Image Processing, Printing and Storage," though to date I don't think the discussions of PS techniques have been as extensive or useful as they could be. Particularly when compared to the very informative (and highly technical) threads comparing and discussing different sensors and camera platforms.
Unfortunately, spending more time playing with PS doesn't appear to be a optimal way to reduce love-handles. If only there were a "history" brush that could be used to selectively repair the ravages of time on our bodies and our lives.
