Have you ever seen a photo and you thought to yourself--wow! That person is awesome. How did they get that photo at that moment?
Well my friends, I'll be the first to admit (even if another photographer doesn't), that sometimes it is accidental! Take this here photo:
I saw this window of students in their class, but I had no idea that this student was going to lean over and smile when I was taking the shot! Afterwards I felt so blessed that I happened to capture it.
There is a phrase coined by Henri Cartier-Bresson (who is known as the "Father of Street Photography" and also for being a master of taking candids) that calls these moments "The Decisive Moment". It's that perfect moment in time, that doesn't last long--maybe just a second, that you catch on camera. I believe that these perfect moments can be calculated, and sometimes not. You have to be looking for them, especially when it comes to people!
When it comes to objects however, you can set it up. The photo I took below, was very intentional. I loved the snow on the branch and I loved the tree limbs in the background with the yellow/blue hues from the sunset. In this case, you could say that if I had waited another 10 minutes, it could have been darker and that exact coloring wouldn't have been there. I wouldn't had caught that moment in time when things were perfect.
So accidental or intentional? I'd say both. I try to be intentional in every shot, but sometimes you do accidentally get that shot you weren't expecting, simply because you were there at the right time and the right moment. I wish it were like that every time!