Best Mac Screenshot Software?

[bdwlecteur]

Long-time BR member but first-time poster here. What's the best software for capturing screenshots of DRM-protected files on a Mac? Have bought and downloaded several titles on iTunes sales over the last year or two for possible use in a film course I'll be teaching next spring, and would now like to capture select frames (like those that show up in reviews here) for use in lecture, but Mac's regular screencap feature doesn't work w/ DRM media. (Not for me, at any rate.) Thanks in advance for methods/apps to streamline this task!