They work, the problem is guessing the right exposure for the image. I would prefer a reverse adapter ring to install the lens on the camera on reverse that will make it a very close, closed up lens. On my Rollei I Install the lens on reverse on the camera and use the camera bellows for proper focusing, it gives me a 3:1 ratio. So even though I have tubes I dont use them. Beside focusing with tubes is a pain in the neck. Hope this help.