Pretty frequently I'm startled by my lack of art knowledge. Sure, most people I know really aren't into art, and have little working knowledge of any medium. To them, I'm sure I seem like I really know what I'm talking about most of the time. And to other, more established, experienced artists, my lack of knowledge isn't surprising at all. There is so much to learn that, even you are devoted full-time to learning about art, there is always something new to discover.
Still, I regularly learn something that makes me think, "Wow, how could I not have known that?" The most recent example is pyrrole red. This is a pigment that was developed in the 1980s, so it's been around a while. It's a relatively inexpensive red, cheaper than the expensive cadmiums. I've learned (through internet research) over the past week that it's a great, versatile color, and very bright. Many artists consider it a very important tool.
I don't have this color. I don't have any reds that have this pigment in it. Get this: this color is also nick-named "Ferrari red." Hey! And I'm painting a Ferrari right now. I guess I'd better buy a tube and check it out.
Another thing I think about, related to the above: I feel like the technical aspect of painting was largely glossed over in my university studies. What did we talk about instead? Well, there were a lot of generalities (don't over-mix the colors…perhaps you want to try more muted tones…etc.). Most of all, I think there was discussion of the drawing aspects of painting, such as getting value right (something that, honestly, probably can't be over-emphasized), proportion, paint application and brush strokes.
I can recall very little discussion, however, of opaque pigments vs. transparent pigments, or having on hand cool and warm versions of the same hue. There was certainly little information presented on glazing, which frankly I'm not sure any student I was with ever really attempted.
I'm not at all faulting any of my professors. They had their hands full just trying to coax us into the ability to paint a portrait with vaguely human features, and I am forever in their debt. The information has always been available for me to learn. Maybe I don't really ever learn something until I truly need it.