If you understand the information you no longer need the original mental image. Just like you understand the word chair can represent many chairs in different styles shapes and sizes. To have one mental image for the word chair would limit you in recognising the related items. It would confine you to having to learn and create a mental image of another chair.
This can probably be better explained by using the colour red for example. You see a picture of a red flower, then a red cube and a red car. If you only had a photographic memory of those three things you could not tell me through understanding what they have in common. You could create a list red flower, red cube, red car and it would be meaningless to you and someone is asking you what they have in common.
There are limits to a photographic memory. Often it's understanding the meaning of the message provided. Once you understand what you've read it makes more sense to own it by putting it into your own words based on your own experience.
This is why I find PhotoReading brilliant. You don't have to read the image in the minds eye later. You understand the information because the brain has processed it for understanding.
Alex
