Casual closeup photography question ...

I have two MD Rokkor X lenses, a 100 f/2.5 and 50 f/1.7. I also have the nifty fifty. What would you folks do-buy extension tubes for the nifty or a reversing ring for the Rokkors? The 100 and 50 are both 55mm filter threads. Will be used with XSi or 50D.

oldvultureface,
What I would do is buy the Canon 100mm f/2.8 macro lens

But from your options I personally would get a set of Kenko - 12, 20, 36mm extension tubes for use with your 50mm lens. It gives you more options as full control over aperture via camera controls and more options for less magnification. ex. a flower just a 12mm tubes with 50mm lens might be enough but for other subjects ex2. an ant more tubes like the 36 & 12 (or more) with 50mm lens might be wanted.

Thanks for the response. I thought I could put the old Rokkors to use but I see the tubes are more versatile with the nifty.

I'd been using a Sigma 105mm Macro lens + Kenko set, but I tried my 50mm 1.8 on the tubes and it produced much sharper images with magnification that didnt seem to far off that of the 105mm macro.

Received my extension tube this afternoon. My old work watch: