Enigmatic Half-Circles

The photow below was taken while photographing nothing but ordinary drops of pure, clean water falling against a dark featureless background. The first one from December 17, 2015 shows a strange half-circle that appeared with a size of several inches.

The second one, from January 4, 2016 shows another semi-circular object:

These objects are what I call orb veils. This semi-circular shape is only one of the many shapes these mysterious things take. Below is a composite photo of many different types. Open up the large image in a separate browser tab to see the image at its full resolution and read the different category types.