Comfortable step height

So I'm building 3 decks, all different levels, one lower than the other etc etc. To create a step down effect.

I'm a little stuck with working out what will be a reasonable height to have each deck. Obviously I want to keep the steps in a uniformed height, so when walking up the decks, it is comfortable to step up, and varying heights may trip the person.

I have the alan staines book but it says nothing about minimum and maximum heights for a step. It just talks about stringers and rise and run..which is all good and proper but this is far from that.
Can anyone advise?

I was thinking something around 135mm would be comfortable.
Is there a standard for such a thing?


More...