To get good photos you have to experiment a lot, to try different things and to stretch the bounds of your camera’s light capturing abilities. This experimentation means that you will have many failed shots initially for every good one, and that over time with practice you will learn the edges and bounds. Here’s a photo where I bumped up against a few.
What I was attempting to do was take a long exposure of running water to give it a dreamy blurred motion effect instead of the “frozen” look you get when you set the camera to auto. This is because the auto setting will always attempt to get you a reasonably high shutter speed for the available light and aperture, which usually means glassy looking still water with all motion frozen in time. Sometimes that’s exactly what you want, but for a scene like this you hope to capture that sense of the water’s motion instead.
I’ve tried this same photo at the same spot a few times, and I’ve never really gotten the aperture / lighting / and shutter speed combo in the range needed. The day I took this it was dim so I thought I’d finally arrived while the lighting was right. It worked but it didn’t because of camera shake.
So to get this I set the ISO to the lowest (100,) the aperture to the highest this lens would go ( f/32) which gave me the desired slow shutter speed of slightly over a half second. The water is almost right, however if you look close every thing else has a slight blur from camera shake because the shutter speed is just too slow to avoid that with a hand-held shot.
So the next time I take this I will have a tripod to prevent that. That will cause the rocks and everything not moving like the water to come out crisp and sharp. Some pros cheat scenes like this by forcing the shutter speed with a neutral density filter, but that’s putting the image through another piece of glass, which ultimately makes it less sharp. So I doubt I’ll ever get a set of ND filters, but who knows.