The normal perception of the photograph is to see it as just a record of something but it is far more complex than that.
Taking a photograph does indeed take the image out of it's context. The 'context' of reality is the flow of time. A photograph is a 'slice' of reality which is divorced from time - a rough analogy is a fly trapped in amber.*
If the photograph is of a specific thing and that is it's importance - a record of a person, a record of an event - it only retains any use whilst there is supporting information: who the picture is of, what was going on, when the event occured and so on.
If this information resides in the viewer's memory then the image is important to them. If the viewer has no knowledge of all of this then the image changes it's function and we look at it differently.
For example: a picture of your mother will be evaluated by you in terms of your memories and emotions. To someone who does not know your mother, the image will be evaluated purely in terms of it being a portrait photograph.
The two viewing experiences will differ considerably.
This is why there are different types of image and it is possible to take images which transcend these complex problems to become universally significant.
This can happen because the image uses the visual codes to transmit emotional content - it acts as an emotional/intellectual trigger to the viewer - independent of the context of the image.
Thus the images
here give rise to a range of different reactions. The American action in Vietnam occured within living memory. Most people will know something of the event. The pictures therefore represent war ingeneral, the Vietnam conflict specifically, a key to emotion if you took part in it, a key to emotion if you lost a loved one in it. It is also important to remember that US citizens will have a different reaction to non-US citizens, who in turn will have a completely different set of reactions to the Vietnamese.
And I have yet another layer of reactions to some of them because I met Don McCullin and I knew Tim Page.
All of this explains, to some extent, why we see pictures we take differently to those taken by others. We have a different memory set surrounding our images - and sometimes this clouds our judgement and makes us wonder why others do not get the same reaction to our images that we do. We have to take all of the above into account and take our pictures differently to do that.
*My current thinking is that the process used to record the image in 2D does so by squeezing out time (time being needed to give the third Dimension). The function of the frame in Photography (to go back to another thread) is therefore not to stop the creative act overspilling but to stop time re-entering the image and destroying it.
I could go a lot deeper with that but I think I've probably lost most of you already
