Is there anyway in which I can turn a celebrity photo into a poster with out infringing copyright?
For your own use it should be OK although it is technically infringement of copy-write.Have a look at the work of the Pop Artist Andy Warhol and see what he did with his prints like the Marylin Monroe series.There are many tutorials in photo magazines and Photoshop tutorials to show how to achieve the effects.Many celebrities commissioned Warhol to do there pictures in his style and some still like to have their pictures done to associate with the “ikonic status” of the real stars like Monroe.Should you wish to use the images for more than personal pleasure it would be wise to contact your chosen subject.