Robert_Charlton - 7:20 am on Apr 5, 2013 (gmt 0)
On a photo site that's all graphics with no text, this fits a pattern I've seen confirmed several times in the past year. When good quality links are pointing to a site, and Google can find no other onpage signals, Google apparently looks at the meta keywords tag (or for any other onpage clue it can find) for confirmation to disable the Google Bomb filter.
Meta keywords - are they worth it?
Meta Keywords still do matter
It's the links that rank the site, though... not the keywords or the image file names.