I now can't believe I committed to a whole week shooting this head of broccoli. Although I'm still committed and struggling a bit, I think this shot is a bit more realistic in color. Andisaw's recommendation to increase the light was a big help. I shot all of my images today in the greenhouse where there was a lot of natural indirect light. I'm still finding the extension tubes to be a bit tricky. I didn't buy the really good ones and I have to manual focus, which could be part of the problem. I'm considering renting a macro lens simply to evaluate the difference. Is anyone using one that they love?
This next image was shot with my little Olympus Tough Stylus camera on the macro setting - no tripod, no timer. It ended up sharper than the previous shot using my Canon Rebel 3Ti. No edits were made. I'm not sure why I can't get a sharper image like this with my Canon.