Zoom lenses in general are not the best candidates for extension tubes. Prime lenses tend to work much better. The reason is that zoom lenses tend to be formulated to converge all wavelengths of light at a particular flange-image distance. Prime lenses tend to be convergent at more distances from the lens flange.
Close focus diopters will work with either zoom or prime lens designs and a 77mm, Canon 500D is a permanent addition to my bag (to use primarily with the 70-200mm, f2.8L). I use an adapter ring to mate the diopter to other lenses.
TBH I primarily rely on a crop 1.6x body and the Canon EF-S 17-55mm, f2.8 IS USM for close focus images like ring shots. While it's not a "macro" by any stretch, it is often appropriate.
This is a 40D plus EF-S 17-55mm @f8 and moderate crop:
Comments
Close focus diopters will work with either zoom or prime lens designs and a 77mm, Canon 500D is a permanent addition to my bag (to use primarily with the 70-200mm, f2.8L). I use an adapter ring to mate the diopter to other lenses.
TBH I primarily rely on a crop 1.6x body and the Canon EF-S 17-55mm, f2.8 IS USM for close focus images like ring shots. While it's not a "macro" by any stretch, it is often appropriate.
This is a 40D plus EF-S 17-55mm @f8 and moderate crop:
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