Increasing contrast adds more 3-D effect to the shot and apparent
'drama'. It's a personal choice.
Increasing contrast often tends to appear to sharpen the image. Things appears to be
more in focus.
Usually altering the contrast is simply a matter of dialling in more or less contrast in, using a
scale or similar (often + 10 to 15%)
Contrast isn't always good. It can highlight backscatter. In some shots there is already
enough contrast. So, experiment.
Close call. Opted for 10% as tend to try to under-do things to retain a natural look when increasing contrast.
The coral improves nicely as does that fish directly in front of it.
Perhaps I should have gone for more
.