Specifically, I wish I had taken a course on optics. I would then understand the inner workings of lenses, depth of field, and apertures. I would also understand why depth of field shallows significantly the closer one gets to the subject. Take for example this photo of a tulip that I took. I was as close as I could possibly get which is about 1.5 feet and the depth of field was incredibly shallow; barely anything is in focus. Granted, the aperture was almost wide open. But really, I want to learn what governs these general rules that I follow when I photograph. I think that it can only help me better my photographing.
Taken with Canon EOS Digital Rebel XTi.
Canon EF 50mm f/1.8 II.
Shutter Speed: 1/640s.
Edited with Adobe Photoshop CS5.