With true jewelery photography you want to have maximum control over the depth of field. There is no way to achieve this with macro lenses alone when shooting rings for instance. Half of the picture will be sharp, and half of it will start to get blurry. Decreasing aperture will yield in loss of image quality. Tilt-shift lenses from canon are quite good but won't get you close enough to the subject in a lot of the cases. If you're serious about it you should look into large format cameras. You can pick them up real cheap these days on ebay. They allow complete movements of the front and back standards. The lenses are superior, and you can purchase them relatively at low cost too. You could probably opt in for Calumet lenses or try attaching an enlarger lens. The plus side to large format system is that you can purchase a plate which will allow you to mount Canon equipment and in the future you can also mount medium format sensor.
