Q I’m looking to buy a new AV receiver. Denon just came out with the AVR-S930H, a 7.2-channel model that’s Dolby Vision compatible. Should I instead buy a 2016 model with similar features minus the Dolby Vision support? It would save me a few hundred dollars. The only Ultra HD source I plan to use it with is a Roku player.  —Steve Guminy

You might be surprised to learn that there is more to contrast than just black and white. The intensity of color matters just as much. While the topic of black-white level has been explained in all its glorious intricacy by the best minds in the AV world, I prefer a more basic approach — one that makes sense to someone who doesn’t know lux from lumens.