At what levels do death timers for champions rise at?

Question

Does the time on deaths rise every couple of levels or a certain amount every level, or is it by the time of the game?

Answer 1

It seems the exact formula is nowhere to be found, however from http://leagueoflegends.wikia.com/wiki/Death :

On Summoner's Rift the death timer scales from 12-50 seconds, which includes a base scaling per champion level and an additional scaling after 30 minutes, increasing the death timer by 2% each minute up to a 50% cap.