The 50mm and the 100mm are prime lenses. Prime lenses are usually a lot sharper than zoom lenses. My advice is don't sell 'em use'em. You will get better pictures and learn more about composition rather than zoom in or zoom out. The previous comment about f-stop is right on too. You can use lower ISO in the same light, which makes for better pictures also. Good shooting...

I have a Slik U212 that will do most anything. A few years ago I was copying old family photos and didn't have, as I do now, a copy stand. SIMPLE... I take my tri-pod, extend the legs all the way, reverse the center post, attach an angle finder to my camera and shoot away. Now I would simply put my Olympus E5 on my copy stand and use the flip screen feature. I think that your instructor was embarrassed because HE hadn't came up with the reversible center post gambit first. I had an instructor do me that way years ago when I mentioned "Hyper Focus" as a good way to take fast action photos. Some instructors are like that.