301 and rel=canonical AGAINNNN

[InternetRep]

Trying to understand rel=canonical if you have proper 301 redirects (redirects to the canonical URl) for example when migrating from a HTTP to HTTPS environment why would you also opt to add a rel=cannonical tag on the same pages. What effect does this have on SERP rankings or is it ok to have 301 redirects and rel=canonicalon the same page? Anyone?

[Igor.Go]

No reason to use both. I would even go as far as to say I wouldn't recommend it.

301 and canonical have different purposes. 
301 forwards user to another page. Canonical removes the page from the index but the user is still browsing that page.
I guess you know that.

I wouldn't want to give Google even the slightest chance to mix it up and read it wrong.