Digitising collections of microfiche - Re: Looking for opinions...

On Wed, 28 Mar 2018, Ethan via cctalk wrote: In other words, a homemade fiche scanner. If you start with a fiche viewer, then a lot of the mechanical parts, such as the fiche holder, are well under way. You need to modify the card movement mechanism to be able to automate it, but you could put that part off until you confirm that the optical portion is satisfactory. But, even when you put in the stepper motors to handle card motion for scanning, you still need to manually load each card into it, and THAT is one helluva lot of cards. Enough to even discourage Al! I s'pose there exists auto-feed fiche scanners, but prob'ly not cheap. You would need to replace much of the optics with a short focal length flat-field lens with a lot of extension. 25mm enlarger lenses, which are usually the cheapest flat-field lenses, are usually pretty available. Most are L39/M39/Leica screw mount (39mm diameter by 26tpi Whitworth. YES, Oscar Barnack really did go metric for diameter but not thread pitch!) which is REAL easy to find adapters to almost any interchangeable lens camera. Some enlarger lenses, however, are the Schneider mount which is 25mm x 0.5mm; those adapters used to be readily available, both for enlarger lenses and Compur 00 shutter. Now it takes a little more looking. Added extension shortens the distance from lens to subject. An added extension equivalent to the focal length of the lens will change the focus give you one-to-one. In other words, adding 2 inches of extension to a 50mm lens will bring the focus to 4 inches from the lens. You want a fair amount more than that. If you will be doing a wide mix of frame sizes, then a bellows would be the right way to go. Otherwise, extension tubes. Both are available very cheap on eBay from China for most cameras with interchangeable lenses. For a non-interchangeable lens camera (NOT RECOMMENDED!), you can add what uest to be called "Portra lens" that attaches like a filter, with added diopters. They are additive, and you will need more than one. They also further reduce the image quality. If you want help with the formulas for extension, just ask. My favorite source for that kind of information is a 1936 edition of "The Leica Manual" by Morgan & Lester. Most important formula is that distance from lens (focal node, not surface of front element) is equal to distance of lens from "film" multiplied by focal length divided by amount of extension. -- Grumpy Ol' Fred cisin at xenosoft.com