SEATTLE — Anyone who wants to learn calculus, statistics or ancient Greek history can take free online courses in those subjects at a variety of sites from instructors with distinguished academic pedigrees. For more mundane pursuits, like learning how to paddleboard or build a planter box for the garden, there is an inexhaustible supply of free how-to videos on YouTube, eHow and other sites.

But if you’d like to watch a recording of a three-day course on the minutiae of photographing clients who commission high-end portraits of themselves in lingerie, that will cost $149 on a Web site called CreativeLive.

While companies like Udacity and Coursera — providers of giant online open courses — are just beginning to introduce courses with fees that count for academic credit, other online learning companies have carved out a lucrative niche in courses on design, photography and other creative pursuits. CreativeLive, Lynda.com and others have tapped into an audience of customers who are highly motivated to hone skills that might help enhance their careers. The online courses are usually less expensive than intensive in-person workshops on photography and other subjects, and can attract top-notch instructors with their promise of big national audiences.

Amanda Picone, a wedding photographer in Babylon, N.Y., bought the CreativeLive course on photographing people in lingerie, a genre known as boudoir photography, because she thought it would enhance her appeal to clients, some of whom want boudoir shots. Ms. Picone learned that asking subjects to lift their chins slightly while posing can result in more flattering portraits.