Fade to grey?

Having been back from the aforementioned Irish trip a while, I was having a flick through my photo's of the adult Kumlien's gull at Reenard point, Kerry:






Then this photo caught my eye:




I thought I had a different bird, one that we hadn't noticed in the field, paler but with still enough grey in the webs to make a decent candidate for Iceland gull. However, I looked again when I got back from Egypt (blog post soon), and there seems to be a bit of a scale in the darkness of grey shown in my photos of Kumliens gull(s) at Reenard, for instance:




I'm now pretty confused. In the field we only had one bird we thought was Kumlien's, which appeared to show charcoal grey in the outer primaries, although most of my attention was focussed on photography, rather than observation. There were certainly a few adult Icelands knocking about as well. Are there two birds, or is the camera just responsible for the colour change?

Any comments gratefully recieved.