It is unremarkable that there are no specific responses to ET's initial comment, "photographs fail to capture the amazing visual experience of these light works". It is remarkable that no one has felt moved to comment on the resistance these works have to reproduction in any form, and to any aesthetic description beyond "you ought to see them". The cleverer the attempt, the worse the result. The Hayward Gallery images, inviting perhaps, are inviting only - they miss all of the work-sense of Flavin's re-building of merely instrumental lights into a specially focused - even rare - beauty.
You only get that when you see them, sockets and all, mounted on a wall that lets them shine unexpectedly with glow and color in an uncommon placement. It stops us in our tracks - each tube has another life utterly beyond its wattage and fluorescence - and we had surely not seen that before with anything like Flavin's invention of each tube as a complete visual entity.
Sorry, I have come up against my own caveat. If you can see only the "Diagonal of May 25, 1963" put on the lower left corner of a partial wall leading to an exhibit (as the Washington National Gallery did) you would be convinced.
-- Geoffrey Cavanagh (email)