Like Meta, I did it in days of yore with film cameras. I did dabble briefly since going digital and before buying a dedicated macro lens. The only two shots in my
Gallery that were taken with a reversed 50mm standard lens are these...
It can be very effective and is certainly a cheap option - a reverse adapter should cost under a tenner.
The biggest drawback is that focusing is a nightmare. When the lens is on the right way round the camera keeps it wide open regardless of the aperture you have set and only stops it down to your selected aperture when you press the shutter button. This is to give either you or the AF system the maximum amount of light for focusing. When the lens is on back to front the mechanism for doing this is disengaged so if you set the lens to f16 it stops down to f16 straight away and the image in your viewfinder is
VERY dark.
Dave P.