There was a case mentioned in a psychology book I had in college back in 2005 about a girl who was the strongest among a set of case studies investigating the concept of a photographic memory. She could recall details from the image for about ten seconds, if I remember correctly, before it faded from memory.
The 'problem' is in how the brain tends to remember things. The brain doesn't remember 'raw' information so much so as it remembers 'quirks.'
When you take a picture with a camera, information is recorded as to the state of individual photocells at the given time of the picture. Every photo cell is recorded and the information is stored to be recalled again. Unless it is compressed, in which case, information about groups of data points is collected. All of this can be pulled up to produce an exact replica upon demand.
However, there is only so much need for this within typical patterns of human behavior. The fact that we bothered to create photographs or that good portrait painters were held in esteem in older societies is a testament to our limited ability to both retain information about exact appearance and our difficulty in communicating it to others through oration.
Put simply, we tend to suck at remembering images and use tools to solve the problem.
This is because, as I said, the brain remembers 'quirks.' It is, you could think of, a sort of compression. You remember that a person is missing a tooth more readily than you could pick out their cheek bone. You remember a hair style more easily than you remember the face associated with the hair style (one of the reasons people look so different to us based on how they wear their hair). You might remember a particular set of freckles a person had or a peculiar stance in their posture.
For example... what color is the couch in the latest AVGN video you've seen? Was he even sitting on a couch? Can you even remember what he was sitting on (or substitute any other video series you may watch)?
We don't have photographic memories because these details tend to get lost. We may remember that there was a pizza box in the background - but from where? In what position? And what was it sitting on, or what was next to it?
The brain remembers quirks and concepts. Everything tends to get reduced to the level of detail you would use in conversation. Even things you remember well enough to 'see again' are heavily subject to the way our brain tends to 'compress' information.
Granted - the exact processes of memory are still being researched, and it is likely that different people have considerably different ways in which their brain remembers information. Some of which may be better suited to 'photographic memory' type things.... but it has, to my knowledge, never been demonstrated for a person to have a truly photographic memory in the sense that they can take a sort of 'snapshot' to look at and pull details from, later.
Another problem arises when we consider the limitations of the eye. If you hold out your hand at arm's length and extend your thumb - your thumb-nail is about how big the area is that your eyes have 'maximum' resolution for. The quality of vision drops rapidly as you extend into the peripheral - where image resolution can be as low as 'feet per pixel' depending upon the exact distances involved.
You must be registered for see images
This is pretty close to how your eyes see things. Because you sweep your eyes very quickly across a scene on instinct to 'stitch together' a scene, it is rare for you to ever have a 'photograph' to work with.
In marketing, researchers use devices to track eye movement and determine where people are looking when they encounter an advertisement and what-not. "heat maps", as they are called, are used to highlight where people spend their time looking at an image:
You must be registered for see images
The colors on the lower images relates to how much time the eyes of people spend there.
In the left image, the model for the product is looking at the viewer - in the other, she is looking at the product - and whether conscious of it or not, people instinctively react differently to the simple adjustment to eye placement.
Notice, however, that the eyes spend very little time elsewhere in the scene. To drive this point home:
You must be registered for see images
The eyes spend a lot of time on the face, do a brief scope-out of the twins, and try to figure out what is with that dark line on her arm.
Since the focal point of the eyes is so narrow and the range covered so contextual - it's difficult to understand how someone could remember that the drapes on the wall behind her had an accompanying blue top or that the display behind her had some kind of red and blue fabric.... unless a point was made to try and grab those details with the part of the eye that can actually perceive them.
