I had to "scan" about 1000 slides for a slide show. My slide/negative scanner is about as slow as most, so that was a poor option. A duplicator would be faster and easier *but* the 1.6x crop camera would cut off a lot of the image (verified by a test).
http://www.bhphotovideo.com/c/product/82193-REG/General_Brand_SD40_Zoom_Slide_Duplicator_1_2_5.html
The duplicator is similar to this but has no zoom. B&H no longer lists them, my friends and I may have bought their entire supply (four).
So, since the image on the sensor was effectively too large, two things needed correction: the slide needed to move farther from the camera, or the lens needed to move closer to the sensor. I did both, sort of.
The internal lens is mounted on a surface facing the slide, it was an easy matter to remove it and mount it on the surface facing the camera. Job one complete! The slide mount has some adjustment by a set of very fine threads on the body of the duplicator, by adjusting the slide all the way out it was very close to perfect focus and almost the entire slide was now captured on the sensor. A 1/4" plate (made of the finest plastic, and painted black to minimize reflections) finished the job.
By taking photos of a sharp slide while adjusting the threaded barrel 1/4 turn at a time I was able to sneak up on the best focus, which is pretty sharp (I can see film grain).
Here is the test slide:
The final frontier: negatives are of course orange and reversed, not much good like that. We need something to correct them once they are "scanned". I found a tutorial to do that in Photoshop but I use a program called VueScan which is made for scanning and can correct negatives as files, in batches. I bet other programs can do that also.
I use an Ott-Lite for a light source, open sky works ok too. The Ott-Lite needs a diffuser and the shutter speed is slow but the duplicator is mounted to the camera, even 2 seconds gives no blur!
Anyway, that's the story, kinda' long but hopefully informative.