Devices like Digital Duplicator de Kaiser are cut-rate accessories that allow you to digitize or duplicate on film a slide and/or negative. The concept is not new; similar such devices are and have been sold over the years. These devices provide a means to hold and illuminate a target slide or negative and take a close-up photo using the supplied camera lens.
There is a problem using the supplied camera lens in that it likely cannot achieve focus sufficiently close enough to achieve the desired magnification. These devices solve the close-up imagining problem by affixing a supplemental close-up lens before the regular camera lens.
In the case of the Kaiser, a +10 close-up lens is supplied. The +10 is optometry speak for 1/10 X 1000 = 100. The +10 translates to being a 100mm lens. When such a lens is mounted before the camera lens, the camera set to infinity (∞) now achieves focus on an object 100mm foreword of the front element. Additionally if you move the focus ring away from the infinity position you can move in closer, an perhaps achieve focus at 75mm lens-to-object.
We can calculate the magnification obtained with a 50mm supplemented with a +10. Set to infinity, the magnification is 50 ÷ 100 = 0.5X. With the distance scale set to 1 meter (3 feet), this add another diopter worth of power for a total of 11d = 90mm lens to object, magnification now 0.55X. Now we know, with a +10 the focusing range is 90 thru 100mm and the magnification range is 0.55X thru 0.50X.
If we attempt to copy a 35mm slide of standard size 24 X 36mm (slightly smaller is mounted), with a magnification of 0.5, the resulting image will be 12mm height by 18mm length. If a full frame camera is being used, the image will cover only ½ of the camera’s frame. If a compact digital is being used, the format size is 16mm by 24mm, the Kaiser will not quire fill the frame.
Would I use a devise like the Kaiser? I would if I only had a need to digitize slides occasionally. The drawbacks are, the +10 supplemental close-up is a weak link. Most will tell you the acuity is not there. My experience with supplemental lenses is OK. I buy achromatic doublets and they work just fine for most needs. Best would be to mount the Kaiser to a macro, these are optimized to work in close.