You don't need analytics. It's right in your raw logs. But it's expressed as "page=" rather than "number=" which raises the interesting question of what happens if the visitor's search prefs are set for more than 10 items per page. Does "page 2" mean their page 2, or "between 11 and 20"?
And forget trying to make sense of page numbers in an image search. The layout seems to change every other week.
If you do show up as Page 5, it would be interesting to know whether the user patiently clicked one item after another through those intervening pages-- meaning either that the snippet text doesn't convey the right information, or :: ahem :: that the visitor is stupid-- or did they keep scrolling through the SERPs until they got to your snippet and said "Aha! That's what I'm looking for!"
And then you'd want to know whether the said visitor entered an anomalous search phrase, or whether most people using the same terms and getting those same results were likewise looking for something buried on page 5? Did the others just give up, or did they glance at page 1 and try a different search phrase?