Was experimenting with long exposure in my front yard.
Left image: 16sec exposure, F/10, 100 ISO. 21mm with Canon 17-40L lens, shot RAW.
Right Image: same image with Photoshop input level cure at 0, 1, 2.
Insert is blowup of area in question.
Took 14 images, this is the only one with the anomaly.
Any ideas what can cause this?