Feature suggestion: new since last login.

I would like to be able to see only the pictures posted since i've last logged in. i know pictures that were posted while i was logged in would also appear, but it seems better than trying to remember "did i saw that already?"

How would you define "last login"?

If you browse the site for a while, go eat something, and come back after 30 mins, is that a new login? One hour? 4 hours? A day?

i'd define as each time you type in your password. but "new in the last 24hrs" would also be cool.