I bought this on ebay to reproduce the many color slides I have. I tried to use my bellows with the slide copier attached and macro lens but could not get a full frame copy. The bellows with the EOS/FD adapter does not allow for the less than 1:1 magnification needed for a full frame copy on a Canon EOS 20D with a 1.6 crop. I have tried to use both my film and flat bed scanner but they just take too much time. Also the scanners appear to make the grain more noticable even though they have more resolution.
This slide copier appears to be just a +10 close up lens attached to a tube with a slide holder and diffuser at the end. It attaches to the lens via the filter threads. I used it with my EOS Zoom 28-105mm f/3.5-4.5 USM and set the camera to AV at f/11. I found that setting the zoom to about 70mm gives me a full frame copy. I shoot the copies in RAW and convert them in Photoshop. That way I have control over the color balance. I can use sunlight or flash for illumination. I am very satisfied with this purchase.