This is a close-up shot of an ice sheet, and the curvy nature of the surface of the ice sheet caused some caustics to form. By having the focus on the ice surface itself, no caustics were seen, as can be seen in the second picture below, where the curvy nature of the ice surface also is visible. But by having the focus slightly in front of the ice surface, the caustics showed up as in the photo below. The colors in the photos are probably caused by a crack somewhere in the ice sheet.
(2015-01-25)
The same scene as above, but with "correct" focus on the ice surface itself. The caustics are no longer visible. (2015-01-25)
Another photo of the caustic effect. (2015-01-25)
Another photo of the caustic effect. (2015-01-25)