Scientists are not yet certain how photographic memory works, but there are several theories.
Perhaps visual memory consumes many regions of the brain that are supposed to be specialized for other purposes. People can have diminished capacity in certain areas such as spatial thinking, social skills, or language, while having extraordinary talent in a single hobby. This explains why savants and autistics have damaged social capacity.
Perhaps enhanced emotion is involved, which would deeply ingrain a memory in a more dense fashion than normal. Perhaps attention is merely extremely focused on image detail. Perhaps there is some elongation of short-term memory, which would solidify image patterns in memory.
Eidetic memory (frickin’ humongous memory storage) can occur for any sense. It seems to me likely that a combination of these theories may be responsible.
imasciencegeek 
Another theory that wouldn’t explain all cases, but helps explain some is that in some people the senses overlap (synthesia). In this way a sound can have a shape, a texture, a smell, a color, and so on. Since, multiple senses are then involved with any particular stimulus, a memory may be even more vivid.
I thought about mentioning that but it felt a little too off tangent. Thank you for bringing that up. I think synesthesia mainly supports the region overlap theory.
Totally fascinating stuff.
Well, this is off topic but the image of the lady is really nice. Are you an artist yourself or do have a source for it? Toodles 🙂
All my blog images I get from google searches on the topic. I do some artwork, but it’s not really anything good.
hm…. you SHOULD use your own artwork. It’s good practice and I bet it’s actually better than you think. People like doodles and sketches! 🙂
It would probably help my skill to practice more often, but it takes a lot of time that I don’t have (I’m a full-time college student). Also, I don’t really have the equipment to scan (photographing sketches make them look horrible).
I know this is two and a half months after the post, but wanted to put my two cents in on how my photographic memory works and how no one told me that this is not normal. I didn’t even realize till college. Anything with a strong emotion attached is always ingrained. However small details and obscure conversation are remembered strongly too and in vivid detail. When a memory is played it feels like there is a projection on my forehead playing what I want to think of and I can look up and watch or just listen. It is almost a non stop conversation and the only times I can get it to stop is while playing video games (probably why I am an addict.) My nephew now 3 is showing the signs of this as well and my sister asked for my advice on the matter and told her to promote it and tell him that not everyone remembers like this to avoid some awkward conversations. A photographic memory is a blessing and a curse because in the bad times it can easily override what you remember and all the bad, angry, and embarrassing memories will take over the screen. One bad thing happens and it sends my chest into serious pain/pressure for hours. Most recently tried to switch lanes and a car was in the blind spot badly and they looked at me weird and couldn’t get it out of my head for around 5 hours. If you want any follow up for journalism feel free to contact me.
Thank you for sharing. Emotional photography is less rare than you think. When disasters happen, people’s brain shuts down most of the brain, except for the flight or fight response, or reptilian brain. Time appears to slow down and people often remember events just like a movie projection. For instance there are people who cannot look at Japanese Kamakazi clips without 9/11 flashing on their brain. Emotional memories are always the strongest. You probably just have an extreme form (are you more in touch with your emotions than other people?).
Some people would say I have a great memory, but it pales to David’s. I’ve played enough music in my head that I’ve noticed my mind has a somewhere between two and three day sound loop. I hear a song, and then after two or three days, there it is in the forefront of my mind. It isn’t too bothersome as I have ways of shunting out bothersome tunes. The exception to this was Gaga’s “Bad Romance”. That damned thing was viral three days later and even piggybacked on the song “Sweet Dreams” to come back out and harass me. Never had a song do that before..nuts!