"The Photoshop trademark must never be used as a common verb or as a noun."
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.