[StephenBatey]

Having reread your previous post, I'd like to offer a further observation. Photography is based on two scientific effects; the way light can be bent by lenses to produce an image, and the effect light can have on certain objects that make the recording of that image possible. These can only be fully understood and predicted if you have some grasp of the science underlying them. And, as you've found, sometimes what is entirely predictable by science can be amazingly unexpected if you don't know the principles. As a simple example, think of the effect of observing a solar eclipse for the first time if you have no prior knowledge of them.

Sometimes you need the science to make sense of the reality. In this instance, you need it to be able to predict which lens to use, assuming you have a choice and also that the exact focal length (and hence image magnification) matters. There are some rather unexpected effects of lens design to be detected in practical work if you use a lens in certain circumstances.

I personally like to know what's going on, and most arcane pieces of knowledge do have a practical bearing when the circumstances are right. I know a lot of things that will hardly ever make any difference at all in practice most of the time; but sometimes they will; and knowing them means that I can either work around them or use them to my advantage.

Switching subjects from lenses to shutters provides an easily seen illustration. If you don't know it, find Laritgue's photo of the Grand Prix of the Paris Auto Club 1912, which is easily found on Google. The effect of the spectators leaning one way and the car the other (giving what Ansel Adams described as the most effectiive impression of motion that he knew of) was anticipated by the photographer, who used the camera in a way that would produce it. It's based on focal plane shutter distortion.

Summarising, you can get what you want from your equipment without knowing these things. But if you know them, you'll realise that your equipment can actually give you far more control than you realised, and you can achieve things that you would never have thought possible without this knowledge. It expands your horizons, and pushes your boundaries outwards. It means that you can contemplate images that you might otherwise never see as a practical possibility.