I went to a nature photography event one weekend. There were several main speakers, mostly professionals, some using slides, firing them up singly, others doing dissolves, and a few others were doing digital presentations, mostly poor (compared to the slides) apart from one which was stunning and compared very well to the slides. At lunchtime a few other amateur photogs got to present their work, and this one fellow, who described himself as "a mountaineer who took photos", had a simple slides & music presentation, nothing hi-tech. (This is the dead time in the day, with relatively few in the audience as they're all out doing lunch and shopping.) He fired up the music, and then manually put up the slides through the normal projection system. They were mountain landscapes, very dramatic light, lots of contrast, and really lovely well observed work. First slide went up and the seconds went past, and a few more seconds, and a few more, and a few more and I started to get uncomfortable - why is this slide not changing to the next I thought? An unfeasibly long period of time went past - waaaaay longer than I'd ever have dared to leave an image up. Then the next one appeared, and the same thing happened - ridiculous length of time passing with the same image in front of me. And the music. And then again after what seemed like an eternity the third image appeared. And then something quite weird happened, the image 'seemed' to change, the slide hadn't been changed, but the image seemed to be 'shifting' in some quite wonderful and unusual way! Almost as if the image content was moving - clouds and light, sort of shimmering, but hard to describe though. I was astonished, and was aware that the guy beside me was looking as perplexed as I was, and fidgeting and wiping his eyes. Then image after image appeared in front of us at an utterly glacial pace, and for the next 45 minutes we were sucked into some quite weird and beautiful visual experience, and each image seemed to dance and shift and change in some very strange and unusual way. After it was over I turned to the guy beside me, Jan Tove, the well known & respected Swedish photographer who was sitting with his mouth open looking as puzzled and astonished as I. "What happened there?" he asked me. "Did you..." and I cut him off saying "Yes yes, I did...!" We compared our thoughts on what we had just witnessed and realised we had both experienced some quite strange and unusual perceptual shift, seemingly related to the length of time each image was left up on screen, and our brains trying to play 'catch-up' when the image was changed. Neither of us could figure it out, so we spoke to the photographer and he seemed unaware of exactly what was going on. We asked about why he decided to leave the images up so long, and he was just casual about trying something different, so you could really look at the images, that he felt giving people a longer time to do that would be good. He was really surprised to have us two babbling at him about some weird perceptual thing that we felt was going on! In many ways what we witnessed eclipsed all the techy dual projector dissolves and all that other stuff we'd seen earlier. It was simple and it was beautiful. But it was most odd. I have never seen anything even remotely similar. Whether the music contributed to the experience I am unable to say. Had I alone experienced this, I'd be curious, but that two of us sat side by side and seemingly experienced a similar effect has left me rather more than curious. I left that simple presentation feeling that I had been led towards another way of seeing. As a photographer of long experience, used to observing changing light, aware of some optical theory, and with an interest in perception, I considered myself fairly competent. However this experience has sneaked up behind me and whacked me on the head! And I am perplexed by it. It was so perplexing I'm not even sure what question I'm posing/asking here! Anyone had a similar experience or got any thoughts or observations?