What is the burden of proof for speeding tickets?

I recently got a ticket from a speeding camera for speeding in a school zone. I contested by mail, asserting that as there were no children visibly present, the ticket was without merit. The Administrative Law Judge ruled that "People who could be children are seen in the far top of the photos and movement can be seen in video.." I reviewed the video and it is impossible to identify specific movement. One of the photos, blown up in high resolution, shows what could be a child partially blocked by a car on a lawn, not on the street. So, does this satisfy the burden of proof? Essentially, the government is saying I could be guilty, therefore I am... ?? Does this constitute guilt by preponderance, or reasonable doubt? Because it is obviously not clear and convincing. Thanks