I just got my 52mm reverse adapter ring and thought it would be good to do a comparison of 50mm lens compared to a real macro lens.  All of these shots were taken on a Canon T1i, 1/160 shutter, and with the use of a bounce flash.

Lets start out with the “real macro” lens, the Sigma 50mm DC 2.8:

A Reversed Canon 50mm 1.8 mk ii:

A reversed Sigma 18-50mm DC lens 3.5-5:

Now just for fun, a 50mm 1.8 mk ii stacked in front of a Tamron 28-300mm (not really enough light, and without a tripod):

Please click through on the images to get a finer detailed shot. I would have to say a reversed lens while taking a bit more work does a comparable job. Now I have to admit the 50mm sigma is much easier to shoot with, since it gives you better aperture control, and autofocus. It is still not bad for the cost of a $10 canon reverse adapter.  I am most happy with the 18-50 Sigma lens as it was the cheapest and out of the box gives a better dof then the canon reversed.