Negative Spaces in Logos

NBC logo

Carrefour Logo
Vanderbilt University logo

American Institute of Architects Center logo

These are just some examples for negative spaces in logo design. They are successful designes aren’ they? but there is a point that i do not understand, our professors say ‘you should not do painting while creating logos’, like these keys, birds or etc. But as all we know these logos are so famous and accepted by most people. I hope one day i will understand what should i do:)

If you want to see more logos with negative spaces you can look at http://www.logodesignlove.com/negative-space-logo-design