Well I do beg to differ from you here .For the year of 2012 17,282$ was the tax free bracket/basic personal amount for one person and 34,564$ for a couple if the spouse is not working.So, if your income is less/equal to that figure you are exempted from provincial taxes only..
However, one has to pay both Federal and Provincial taxes .The Federal tax free income bracket/basic personal amount for Feredal taxes is only 10,822$ for one person and 21,644$ for a couple if the spouse is not working.
In order to be exempted from both Federal and Provincial taxes your income should not exceed 10,822$ as a single and 21,644$ as a couple.So,if you earning anything more than 21,644$ (as a couple) ,you are exempted from Provincial taxes (for AB) but you still need to pay Federal taxes .
The exact amount can be calculated at the following links:
http://lsminsurance.ca/calculators/canada/income-tax
http://www.finance.alberta.ca/calc-script/pit-assumptions.htm