Each "fair use" is established on a case by case basis. There is no predetermined amount of copyrighted material that can be used.
US Copyright Law sets out criteria that has to be considered before something can be judged to be "fair use"
# The purpose and character of the use, including whether such use is of commercial nature or is for nonprofit educational purposes # The nature of the copyrighted work # The amount and substantiality of the portion used in relation to the copyrighted work as a whole # The effect of the use upon the potential market for, or value of, the copyrighted work
You may use copyright protected material when you are the copyright holder, or when you have permission from the rightsholder or an exemption in the law. The most notable exemption is fair use or fair dealing, which allows certain limited unlicensed uses in situations such as education and commentary.
Infringement is the use, without permission, of copyrighted material that does not fall under a "fair use" or other exception to copyright law,
Unless it would fall under "fair use" no it is not "okay" to use copyrighted material without permission
If there is no "fair use" exception the only way to legally use copyrighted material is to obtain permision from the rights holder.
Under fair use, using copyrighted material for commercial purposes, reproducing the entire work, and causing financial harm to the copyright owner are prohibited.
There is no set limit of copyrighted material that you can use. Fair use is determined on a case by case basis.
In all likelihood no.Ostensibly your portfolio is designed to generate revenue for you. This would be a commercial use of the copyrighted material and would probably disqualify it as "fair use"
Fair use or fair dealing clauses in copyright laws allow certain limited unlicensed uses, for purposes such as education and critique.
For certain limited uses covered by fair use or fair dealing, no permission is required; otherwise, you can legally make copies if you have permisison from the copyright holder. Unfortunately there is never a straight answer on what uses are fair; fairness is only decided in court.
No, not without permission, or, you feel confident your usage will qualify as fair use. Fair use usually demands that the use be for non-profit purposes, so commercial use is generally disqualified.
In the US, section 107 of the law allows certain limited unlicensed uses; it has a longer name, but is usually referred to as "fair use."
Many educational publications specifically license classroom use. Limited photocopying and other unlicensed uses are often covered by the fair use defense. There is an excellent discussion of copyright for educators at the link below.