I went to see this twice when it was on . I think generally it was very good, but at the same time have needed quite a bit of time to let the ideas settle in my mind into some sort of writeable-about-thing. The exhibition was arranged according to the elapsed time since a wartime event  took place, with the early rooms containing pictures that took place seconds or minutes after an action working up to the final rooms which were distanced from the action by a century or so. I suspect this applies not only to photography focused on war but to anything photographic that is dealing with the past.

What follows are my distilled thoughts, three months after…

The exhibition starts with pictures taken moments after something has happened, a puff of smoke hangs in the air over an Afghan field; dust hangs in the air after a roadside bomb has gone off in Iraq or a marine stares blankly out at us from the streets of Hue in 1968…

These are the pictures that contain most obviously what  I think work best – the ones where there is something in the air (even if, in pictures made years later, that is only a hint or a photogram caused by solar radiation or even just the datestamp of a cheap film point and shoot alerting the spectator to the picture’s having been made in August, of the sky in Japan, during the anniversary window of the 2 1945 A-bombs), something that links the depicted scene to a past event. Some of the later pictures seem to have no discernable link to past events within the frame; rather this is supplied by the title, or the commentary.

Eventually recording history and the places where history happened becomes a question of “this is” or of “this was”; the poison of the past dissipates (where it does not fester) and it becomes harder to discern the horrible and the dreadful. The Armenian genocide is there in the archives if you know to look for it and the Nazi party buildings in Munich are still there if you’re allowed to know that that is what you’re looking at, but there that something in the air has to remain.

For this reason, I am uncertain about whether I think Chloe Dewe Matthews series Shot at Dawn works at anything other than an intellectual level, dependant on our reading supporting text. They have impact, but only once you have absorbed the contextual meta-text around them. Possibly for this sort of thing you need more things that speak of people, and the actions of people, rather than just pictures that could – without the explanations – be moody landscapes. Maybe in 100 years history can evaporate; Culloden can be just another peaty bit of land just south of Inverness; Scapa Flow would be just Scapa Flow if it wasn’t for the rainbow film of  oil seeping out from the wreck of the Royal Oak.

Generally though, I thought that the work that was less obvious in its apportioning of blame worked better. The Lebanese car bomb sites for example or the very dry, but utterly gripping A Living Man Declared Dead pictures by Taryn Simon which – whether they dealt with the culpability a Nazi bureaucrat or the missing men from a Bosnian family – said something deeper about war and atrocity than a simple message of elapsed time.

Gradually I realise that at the core of many of these pictures there are questions of either our (as citizens of the UK) culpability in the events portrayed or else accusations leveled at others. This is particularly the case with the pictures of Hiroshima or Nagasaki or Dresden, but the same accusatory tone is there in the pictures of ruined northern France in 1918 or those of Auschwitz or of the wolf’s lair (Hitler’s east prussian headquarters) photographed in 1960 by Jerzy Lewcyznsky). War is someone’s fault and there will always be people to lay blame on.

Stephen Shore’s pictures of Ukrainian holocaust survivors, their houses and their possessions speak of ordinary people who survived (so becoming extraordinary) and highlight all the other ordinary people who did not. They are concerned with humans  and so connect us to history in the way that some of the other pictures do not.

Many of the pictures in this exhibition deal with the background to my youth (I was born in 1964, my parents were adults during world war two, I lived less than a mile from one of the main fleet anchorages and  the bomb, the cold war, Vietnam, the holocaust, Northern Ireland, the Berlin Wall were present events, rather than history.

I would argue that – say – Don McCullin’s pictures of the erection of the Berlin Wall are as minutes after (or during, even) as his picture of the shell shocked marine in Hue rather than 16 years after the end of world war two; they are no more about the past as his pictures of a gang posed among the rubble of Finsbury Park bombsites in the late 50s are about the blitz. “Years After” distances us from events; many of these are still present in some way, particularly those that deal with the middle east, even though there is nothing relating to Israel, or Korea or the Falklands, or, or, or…

Lastly, it is interesting how the context of two exhibitions (this one and Constructing Worlds at the Barbican) which I visited at much the same time changes the way you read the same images from Simon Norfolk’s Chronotopia (2001-2) – photographs of destruction in Kabul taken shortly after the fall of the Taliban. In this exhibition they seem to be about the still-echoing gunshots that have pocked the concrete surfaces of the ruins; at the Barbican they seemed more in the spirit of Shelley’s Ozmandias, showing the ruins of buildings built by the once-mighty  (here, the Soviet backed Afghan regime that had preceded the Taliban’s rule) and so hinting at the possibility that the things put in place by the Nato allies in the years to come might suffer a similar fate.

I enjoyed the exhibition, but suspect that what I will take away and be able to apply to my own practice is more concerned with the methods of displaying pictures  – the room filled with Sophie Ristelhueber’s large prints of the immediate aftermath of the first gulf war say, or the collaged pictures and transcribed interviews dealing with refugees in D R Congo by Jim Goldberg and Kamel Khelif  – than with this largely post hoc way of rationalising meaning in relation to time. Photography freezes chunks of time; we then look at the past through those chunks’ the elapsed time since the shutter opened and closed again or since something happened in the place photographed is not the only way of organising these pictures’ meaning. But it is a thing to think about.

And the exhibition did bring together many pictures that I wouldn’t otherwise have seen…