My advice would be to simply get a set of Macro Extension Tubes that support AF and aperture control and use those with the lenses you have.... The 18-55mm set to 55mm or the 55-250 set to between 55 and 100mm or so.
There are inexpensive macro tubes selling for around $75 for a set, not fancy, plastic bodied but with metal bayonet mounts. Zeikos (also sell as Bower, Vivitar, ProOptic and a bunch of other brand names) that have sort of odd sizes in the set: 13mm, 21mm and 31mm. Opteka just stared offering a set too, for around the same price, but with more traditional sizes: 12mm, 20mm and 36mm.
Canon sells 12mm and 25mm tubes individually. So does Kenko, who also offer a set that included 12mm, 20mm and 35mm. All these are more expensive than the plastic bodied tubes, but are definitely better quality, too.
Do not waste your money on the really cheap Macro Extension Tubes... Under $25... Sometimes under $15. They lack the electronic contacts, which means no AF and no aperture control. No AF isn't all that big a deal, it's often easier to use manual focus techniques for macro, anyway. But no control of the aperture is a pain in the arse (there is a work-around, but it's really slow, involved and fussy).
There are two ways to reverse lenses.... One is to reverse the lens right on the camera. The other is to reverse stack a lens on top of another lens on the camera.
Reversing the lens right on the camera means no AF and no control over aperture control if using modern AF lenses. Vintage manual focus lenses, which have an aperture control dial right on the lens, can be used. BUT, CANON FD IS NOT USABLE. All FD lenses stop down to f5.6 when removed from the camera and remain there. In other words you cannot change the aperture by changing the setting on the dial on the lens, without a special, hard to find device that installs like a rear lens cap.
Even so, a reversed lens makes for very high and difficult to work with magnifications. It will almost always mean using a tripod and often you will need auxiliary lighting (at a minimum, a portable flash and an off-camera shoe cord).
A reversed and stacked lens is a little different and more practical. This is usually done with two prime lenses, is difficult or impossible with zooms. Often a 28mm or 35mm lens is reversed on the front of a 135mm, for example. Ideally the two lenses should the same filter thread size. That makes it easier to get a stacking ring to join them together. The lens on the front act like a high quality diopter of sorts. You'll be somewhat limited to a range of fairly high magnification. The rear lens still provides control over the aperture, though AF probably won't work.
By the time you set up either type of reversing rig, you'll most likely have more than $75 in it. So it would likely be easier and cheaper to just get a set of Macro Extension Tubes to experiment with. That would be my recommendation. They are very versatile and come in handy for many things... I always have a set with me (sometimes even use them on macro lenses).
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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