Straightening/flattening warped 35mm slides for scanning

[srosenow_98]

UPDATE:

After a bit of thought I opted for a 1:1 Slide Duplicator on eBay that was well within my price range and it didn't require any extra expensive components. 

There was one major drawback, however: My camera is a Nikon D5500, an APS-C sensor camera incapable of capturing full-frame images and thus, on a technical merit incompatible with my slide duplicator (it requires at least a full frame digital SLR to capture the whole slide).

Alas, I had an epiphany. As I am also a veteran astronomer and astrophotographer, the way we shorten the focal length of a telescope and increase its field of view, is by way of using a focal reducer/field flattener. 

Knowing this, I set out to increase the FOV of the slide duplicator by inverting the principle used in telescopes, in which the focal reducer/field flattener is placed at the eyepiece end. (For reference, a focal reducer and field flattener looks like a set of magnifying lenses).

In my case, I took a 3-X Barlow lens (a pairing of concave lenses which, interestingly enough, triples the magnification at the eyepiece), and placed it ahead of the optical lens arrangement within the 1:1 Slide Duplicator.

 

It took a fair bit of finesse to reach sharp focus (including the use of double-sided mounting tape and a few spare slide mount blanks on the end of the slide duplicator) but tests are quite impressive! 

 

For anyone with an APS-C sensor camera, here is how I did it. (Pictures attached!)