In Japan, my girlfriend and I had many experiences with these "orbs" of light, sometimes referred to as "DC monitoring lightships". At first, I thought they were caused by water spray on the camera lens, but I was wrong. Their appearance and disappearance is a complete mystery to me... Also, the common explanation that they are caused by dust particles and/or the camera flash are not valid, as these pictures were taken without a flash.
My girlfriend was much better at "summoning them" than I
And the most curious thing is, when you ask them to go away, they do!