After my mother died and my father sold his house and moved, I ended up with all the old family photos, as I was the only one who had aspirations to do anything with them. The photos included both prints and slides. But most of the older images were on slides, including those of my father in the Navy, when he bought the 35mm camera the slides were shot with.
Converting the slides to digital was going to be the most specialized part of the project, as they would require a dedicated device to digitize them.
I started looking into slide scanners years ago, and they varied widely in price and quality. Since most of our slides weren’t in that great a condition to begin with, I didn’t see the need to buy an expensive professional grade slide film scanner.
The biggest shortcoming I saw with all the scanning systems I found, besides the price of many of them (especially the professional slide scanners) was the amount of time it took to complete the scan. Scan times ranged on the low end from from 20 seconds to minutes per slide, depending on the resolution used and the processing options selected.
Since my family slides weren’t taken with a high quality camera to begin with and had degraded somewhat over time, it struck me as overkill to spend too much time and money to get high quality scans of what were mostly low quality slides.
And of course, the longer it would take me to digitize the slides, the less likely the project was to be completed as well.
I tried a few inexpensive scanning options, including flatbed scanners with slide options, and a cheap dedicated slide scanner, that inadvertently became unusable when I converted my operating system to Windows 7 as there were no Windows 7 drivers available for it.
None of them produced results that I felt were worth the time it took to scan a slide, so I decided to try a slide duplicator (sometimes called slide copiers) for my digital camera.
Since I own a Canon Digital Rebel XT, it made sense that if I could simply take a photo of the slide it would be the most efficient method of digitizing all my slides. Theoretically I would end up with a reasonably high resolution photo of the slide.
There are a variety of sub-$100 slide duplicators for sale from several retailers but at the time it was cheapest on eBay (around $50) so I bought it there (called an “HD² Slide Copier”). Reviews on these types of devices are mixed; some people claim they work fine, while others say they’re terrible. Certain brands also get better reviews than others.
These types of slide duplicators are pretty simple devices, consisting of only a convex lens (a magnifying glass), a tube, a slide holder frame (capable of holding 2 slides), and a receiver for the frame with a light diffuser.
They all require a camera lens of a certain focal length in order to focus properly.
The assembly screws onto the camera lens (I needed a step-up ring too to accomplish that), and the slide holder assembly rotates to align the slide properly within the camera frame.
I digitized a few slides with the duplicator, and found it a very efficient method of digitizing the slides, taking only a second to take the photo, and a few seconds to transfer the image to the computer. Of course it would require some manual cropping of the images later, but the photos were digitized, and that was the biggest part of the exercise to me.
But after using it and examining the images closely, I immediately discovered a significant shortcoming to to the system. The images had serious softening (focus) problems on the edges of the slide. The centers of the images were in focus, but the edges were blurry. (You can see examples at the end of this entry.)
That’s an inherent limitation of lower quality convex magnifying lenses. There are probably slide duplicators with higher quality lenses that avoid this problem to greater degree, but mine certainly didn’t.
Since the center portions of the images were in focus, logic told me that if I could replace the lens with one that would magnify the image within only the central part of the magnifying lens, that the distortion from the edges of the lens would be reduced (that was in lieu of locating, buying and testing a high quality lens, of course).
Since my slide duplicator was useless in its current form, I decide to modify it to eliminate the problem.
I would use the lens mount, and the slide holder/diffuser assembly and replace the lens with another larger diameter one, avoiding using the edges of the magnifying lens.
My first thought was to use the 3.75″ lens in my cheap magnifying lens combo I bought at a dollar store.
But then I found two 3.75″ convex lenses in my parts box that would also suffice. I first had to determine the focal length of the lens (the focusing distance for the camera from end of the camera lens to the slide itself) for the purpose and found it to be around 3.5 inches.
My replacement lens didn’t magnify quite as much as the lens it was replacing, but in testing I found the larger lens definitely eliminated the softness around the edges of the image so it was an acceptable trade-off to lose a little resolution in the process.
Here’s a size comparison of the original duplicator lens and the replacement lens.
The new duplicator assembly was made by disassembling the original duplicator and cutting both ends off the tube at the proper length. The tubes were fit into holes in wood discs that fit inside 4″ PVC plumbing pipe cut to length.
Here are the parts primed with rust colored primer. The original barrel/tube is masked with green tape.
Then the entire assembly was painted flat black.
The lens was mounted inside the PVC tube sitting on four screws with shrink wrap tubing over the exposed ends of the screws. The end cap has rubber pads on its underside that secure the lens.
I used aluminum tape to seal the business end of the new duplicator.
The results were much better than with the original duplicator and completely acceptable for my purposes.
A couple of caveats though: the new assembly is too heavy for the camera lens to autofocus properly, which is not big deal because once the focus is set for the slides it remains constant. To avoid putting stress on the autofocus motor I turned it to manual focus. The weight of the assembly should probably have some additional support to avoid damaging the lens itself and the screw mount.
Additionally, I lost some image resolution with the new duplicator. The cropped images from the original duplicator were about 25% larger than the new duplicator.
Here are some examples to compare output from the original duplicator with the new:
Original duplicator image (note the softness on the edges):
New modified duplicator image:
Comparison of edge detail of original duplicator (on left) versus modified duplicator (on right):
I think it’s clear that the results from the modified duplicator far exceed those from the original.
Regardless, based on my experience and the mixed reviews they get online, I can’t recommend the sub-$100 slide duplicators/copiers (and I can only assume that the cheaper they are the more likely they include an inferior lens and resulting poor performance) , but then you do get what you pay for, so caveat emptor.
If you have reasonable expectations of slide duplicators, you might be satisfied with the results, (as long as you get one with a reasonably good lens).
Otherwise if you’re handy enough and so inclined you can try building your own! The biggest challenge there would likely be making the slide holder assembly and light diffuser, which is the main reason I chose to simply modify my existing duplicator.
Now it’s just a question of plowing through and digitizing all the slides (again)…