For many people, photos are their most treasured possessions. Maybe you have a collection of photos you took yourself, or that a family member took. But if those are in an obsolete analog format like slides, it can feel like those memories or family heirlooms have been lost because there isn’t an easy way to view them. But if you have a decent DSLR camera and some technical skill, you can do what Bryan Howard did and convert an old slide projector into an automatic scanner.
Because there isn’t much use for them anymore, you can find used slide projectors for very affordable prices at thrift stores or on eBay. Howard was able to use one of those to build a scanner to digitize approximately 200,000 Kodak slide photographs that had been taken by his father over the span of more than 50 years. His modified projector does that efficiently by taking a stack of slides, loading one in front of the projector, snapping a photo with a DSLR camera, and then moving onto the next slide in the stack. Each slide takes just a few seconds to digitize.
If you don’t want to go the DIY route, there are commercial scanners designed for exactly that purpose, but they’re expensive. The SlideSnap Pro, for example, costs thousands of dollars to purchase and hundreds of dollars just to rent. Howard’s setup is far more affordable, and you’ll just need a projector that’s compatible with your slides and a DSLR camera that can be remotely triggered. An Arduino is used to coordinate the slide loading and triggering the DSLR’s shutter. The particulars of how exactly you’d do that will depend on your projector model, but you can read through Howard’s build log to understand the basic process.