Sometimes mistakes in photography can be the coolest thing.
I didn’t have the neutral density filter I needed to get a picture of the annular eclipse on Sunday, 2012.05.20, but, I was determined to get a picture of some type that would show the stellar event. To get a reasonably exposed picture of a person with the crescent sun behind him, I tried variations such as using the flash on full power in high speed synch mode, 1/8000 second, f/22, 100mm lens, focused a couple of feet behind a person who is at close distance… the flash just wasn’t powerful enough to do it that way (and, it is a powerful flash unit).
I was a little bit frustrated, but, being the addict to photography that I am, I started trying stupid things, like, putting everything on auto mode. I knew the sun would be way out of focus, but, I was hoping there might be a crescent shape in the big blotch of light where the sun is. I didn’t get that. What I did get, though, was a reflection within the lens that put a small, perfectly exposed, reasonably sharp crescent on the guys forehead! Very cool! Understand, I am using one of the best lenses available (Canon 100mm f/2.8 IS L macro), but, no lens will make pictures without artifacts when shooting directly into the sun.
I certainly couldn’t see the artifact when I shot the picture. The image in the viewfinder was way too bright for me do any more composing than squint, point the camera toward the person, let the auto-focus do its thing, and take the picture… no more than 1 second. Having the lens focus an image of the sun (that’s basically what you were doing when you used to roast ants with a magnifying glass) on the shutter curtain can damage the curtain, so, I knew I had to work fast.
The picture as it came out of the camera was pretty good, but, in Photoshop, I did make adjustments to Fill Light, Blacks, and Brightness, to give it a little more drama.

Lens flare causes crescent from a solar eclipse to appear on forehead