Richard, you've obviously never known a person with a true photographic memory..these people are amazing. A person with a TRUE photograhpic memorie does understand what he/she reads instantly. Gerenally though these people want nothing to do with their gift-or are otherwise incapable of putting it to the best use(mostly from complications due to physical disabilites).There are those who can memorize quickly and then gain understanding, but that is not a true photograhpic mind.
There is insufficient scientific proof of photographic memory. It is widely accepted to be a myth. This is not to say that there are no people with incredible memories, or the ability for incredible recall...Kim Peak. Kim of course is a savant, but the studies on him are on going, and he is but 1 out of 6 billion people. For a story that brings this to light please read the following.
The larger issue, of course, is that a perfect memory wouldn't make a person a grandmaster. It wouldn't even make them a Class B. In ten or fifteen moves you are out of book and looking at a position that has never been seen before in the history of chess. You may have memorized a lot of similar positions, but applying that information to a unique situation is another matter entirely. Data is not knowledge, and knowledge itself is only a part of skill.
so stop laughing. NOW. this is serious business, mister, and you're about to be in for a whole world of pain.