The Photograph makes no sense

There are several reasons why the photograph with the 'disappearing siblings' doesn't make any sense.

The way a photo works, is basically 'capturing and interpreting' photons that hit the camera lens. It doesn't even matter if it's a film camera or a digital one, the principle is the same when it comes to photons.

So for a camera to see something, photons must enter the camera lens, probably radiating from something else, like a sibling or their tacky T-shirt.

Now, the 'his head's gone, like it's been erased from existence'-idea is great, I can imagine someone getting chills from that moment. However, since we understand how a camera works, WHAT did the camera and the 'cameraman' see when taking the picture, when the head was gone? Was someone just casually taking a photo of a HEADLESS MAN and his headful siblings?

After all, we see the bushes behind the head, which means the photons that would've hit Dave's face and then radiated into the lens, now hit the bushes BEHIND his head and straight into the lens, because the head is no longer there. How can we see the bushes but not his head, if his head was there when the photo was taken?

Also, how would the siblings not react if the head of their brother is suddenly disappearing? Surely they wouldn't be able to just casually pose for a photo. To add, wouldn't Dave's now dead body just collapse on the ground?

I know it's supposed to be sort of 'symbolic', but how does the camera know that? WHAT was the cameraman (I am just using this term, get over it) seeing while taking that photo? Was the timeline constantly altered from 'hairless Dave' to the 'headless Dave' to the 'mostly bodyless Dave's legs'? Why would someone take a photo in a situation where someone's legs are just standing on the ground?

Not to mention the whole 'timeline changed, so everyone is different, but yet they took the same, exact photo at the same, exact place with the same tacky T-shirts', not to mention there had to be someone taking that EXACT photo even if there were no people there.

You can't just have someone disappearing in the photo and have the rest of the photo remain the same and have it make sense. Butterfly effect dictates their family would've been vacationing somewhere else, they would've used a different camera to take a different photo - heck, they might not have even taken that photo, they might have taken just video since they could afford a portable television studio at that point.

So did someone take the exact photo at the exact place even without any people? Otherwise, we shouldn't be able to see the bushes and such behind 'fading Marty' and such.

The more I think about this photo, the less sense it makes. What did the cameraman see? IF he and the camera always saw 'three people in front of the background', then the camera should NEVER show us what's behind them. So at SOME point, photons from the bushes DID hit the camera lens, so there couldn't have been any people there - someone took the exact photo without any people in it!