It doesn't happen often but this photo brought it about. It was taken by one of my grandsons. I saw the picture and was looking at it and then 'saw' the grandson taking it. This image changed because he might have been kneeling on the grass or bending down or maybe standing back and zooming in.
I don't know what this phenomenon is called. It has occurred often enough to warrant further attention and increased awareness. It has happened once while gazing at a painting – catching a glimpse of the artist at work – but mostly with photographs.
Often enough in life I have risked voicing unusual observations to have other people respond with similar experiences and saying "I didn't know anyone else had this happen."