Yeah the flare can be annoying, sometimes it works well but with the last few I tried they didn't turn out. And thanks! For their cost I am really surprised how well they work. Since there is no glass there is no image quality degrading. The Kenko tubes also maintain AF, which for macro stuff isn't really important but it's still nice every once and a while.
Thanks Greg. Yeah that one was with the 85mm. I had all three tubes stacked - 12, 20, and 36. It was just lit by two house lamps. I brought this small garden in a tub inside so I wouldn't have any wind to deal with for longer exposures. I wanted to try focus stacking too but didn't get it right. I mention Vivitar because the lens is sold under a few names and people will search for any of them, polar, bower, walimex, rokinon, vivitar, samyang, and falcon. Optically they are all the same but some are priced differently and look a bit different on the outside.