I've never had trouble with the Epson 3200 film holders as far as Newton rings are concerned. I've also made my own film holder which doens't cut off as much on the edges, but also doesn't grip the film securely. It also doesn't produce newton's rings. It may be that for some reason my film is more rigid.
The last time I tried the film both sides up and compared, I couldn't tell the difference. Perhaps I should try again.
I've always assumed that Epson tells you to keep the emulsion side up so the resulting scan won't reverse left and right, not to get a better scan. I believe the scanning software is designed to work with reflective scanning, and without a reverse built in for film, it would normally reverse left and right if the base side were up. Of course, they could have implemented a reversal in the firmware or software when doing film, but they decided not to for some reason. If anyone has any further light to add, please do.
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