Usage guidelines

As you'll learn in Adobe's handy Grammar and Trademark Law (combined) 101, Photoshop is not a verb:

Trademarks are not verbs.
CORRECT: The image was enhanced using Adobe® Photoshop® software.
INCORRECT: The image was photoshopped.

Trademarks are not nouns.
CORRECT: The image pokes fun at the Senator.
INCORRECT: The photoshop pokes fun at the Senator.

Always capitalize and use trademarks in their correct form.
CORRECT: The image was enhanced with Adobe® Photoshop® Elements software.
INCORRECT: The image was photoshopped.
INCORRECT: The image was Photoshopped.
INCORRECT: The image was Adobe® Photoshopped.

Trademarks must never be used as slang terms.
CORRECT: Those who use Adobe® Photoshop® software to manipulate images as a hobby see their work as an art form.
INCORRECT: A photoshopper sees his hobby as an art form.
INCORRECT: My hobby is photoshopping.

Yes, a repost from the weasle