When I bought this, there was limited information in the description, so I bought it thinking it isn't much money, and it could be returned if it didn't do what I hoped it would. Stuff I wish I was in the description when I bought it: This adapter allows you to mount a fast lens with a 52 mm filter thread backwards on your F mount camera. This must be used in full manual mode on dslr cameras. This worked as intended with our f1.8 35mm lens. This will be less useful with slow lenses, because there won't be enough light to find focus. It worked, but not well enough to try to get any pictures with the 55-200 lense at 55, and didn't work well at all at 200 (to dark to see focus). On our 55-200 zoom lens at least, the zoom ring works as a focus ring, making it so you can get perfect focus on a tripod without a macro mount or moving the tripod. A fast extending barrel zoom with an aperture ring might actually be better with this than a macro prime lens (other than the the manual metering issue many cameras will have with that arrangement). Old lenses might have convenient aperture rings, but modern lenses will require you to manually adjust aperture against minor spring tension. At first I thought I would jam the aperture open with something (delicately), but it turns out that you need to adjust aperture to get good shots handheld. This is because you need light to focus, and you need depth of field to get good macro shots of most stuff (the F1.8 35mm reversed and set to f1.8 doesn't have enough depth of field to put the top and bottom of the mint mark on a coin in focus at the same time). If this paragraph doesn't make sense to you, you are unlikely to be happy with this item. With our 35mm lens reversed, we get somewhere about 2:1 reproduction ratio. That is both awesome, and somewhat frustrating. It is frustrating in that since working distance is how you focus, you can't back up to get a bigger area in the shot. It appears that longer focal lengths give lower reproduction ratios and greater working distances. Still, the image quality we get is stellar (as good as the F1.8 35mm nikkor is capable of frontwards). Unlike the screw-on-the-front macro adapters, or diopter filters, etc, the image quality seems to be as good as the lens you use it with. So picture made with this are harder to make, but excellent quality is possible, not just "excellent for the price." I freaked out when it wouldn't come off of the lens. No worries. The proper procedure for using this is to install it onto the lens finger tight, then install the lens onto the camera. When you are done with it, REMOVE THE LENS first, then the adapter from the camera. This does not have an extremely tight fit to the camera body, and pressing the release button, it comes right off. Update (12/2013): Shortly after the original review back in 2010, I ended up installing this to an old underwater camera lens purchased at full retail (used) for $15. The underwater lens is awesome in that the glass is excellent for the price I paid, and the manual aperture adjustment is a knob that protrudes from the side of the lens body. It was only so inexpensive because no one uses the camera mount it is made for anymore. I highly encourage others to use the same trick. The best photos I've ever taken (ignoring the value of documenting family events)have been with this reversing ring and the $15 old underwater lens. This also avoids the problems some others have had (which I have not) of getting the ring stuck on a nice lens.
