Ahh. For brevity and clarity’s sake, we must separate explaining the process into a couple of segments. Capturing the image and developing the image .
We’ll start with the capture since it ‘must’ come first.
As I go out at any given time, I am looking to see something which moves me — gives me peace, joy or excitement. Often, they overlap together in some fashion.
I can get excited seeing the power of a big wave crashing upon a rock, exploding its salty white metamorphosis in the air at lightening speed. To capture this in a frozen millisecond is quite challenging.
One can easily guess one challenge — the speed of it.
The speed is but one challenge. The second may be even more of a challenge. The exposure. As a professional photographer, one would set manually the opening of the iris [shutter wide to narrow], the length of time opened [shutter speed] and the sensitivity [ISO]. This is determined by the combination of what is in the picture frame along with the light which is hitting it.
Studio shots and landscape shots have the time to fine-tune to get the perfect exposure.
So you set your exposure by the scene and light you are seeing, then in the twinkling of an eye, the exposure ‘drastically’ changes and that big explosion of whitewater is ‘over exposed’ — throw away that pic.
Trying to anticipate, one never knows just ‘how much’ white will come into the picture in that millisecond. Part calculating, part guessing, part luck.
We have not even addressed the issue of focal point — to have the premium part of the explosion in focus. You do not know where each speedy little droplet will be. To rely on an ‘autofocus’ is not comforting because it can easily get confused as to what and where, and that is ‘if’ it can process fast enough [likely not].