At what point is it ok to shift to the first name?

[ItsFreezingUpHere]

Ok, I'm pretty sure this is a stupid question, but at what point is it ok to shift to a first name basis with professors? It's been my experience with some professors that it's pretty clear when you can and should start to address them by first name, especially when they're relatively younger or more laid back. However, with some of the older and more "traditional" professors (like beards and elbow patches on the sport coat), I can't help but feel as if it's more appropriate to address them as Professor So-and-So. I'm sure this urge comes from my childhood when my dad insisted that I address older people (like people older than him) by Mr. or Mrs., etc. Any thoughts?

[Eigen]

This is best explained by the following chart:

As well as the preceding strips.

[virion]

I usually notice a change in email signature over time.

Dr. Franklin Lastname

Franklin Lastname

Franklin

Frank

[splitends]

Haha...this was such an issue for me! I was fairly close with my professors in undergrad, and the ones that knew me well would often sign emails really informally, as in "-mike." But I never felt comfortable actually calling them by their first names. I would just avoid it in person, but emails were awkward and I usually stuck to Prof So-and-So. It wasn't until after I officially decided to accept their offer to the grad program that the DGS emailed me back (I had sent in an email saying Dear Prof So-and-So) saying "For goodness' sake, just call me Heather!" Now it's all first names. I think you're probably safe sticking with titles as an undergrad, then switching to first names in grad school. If you don't feel comfortable, err on the conservative side.