OK, here's a follow-up and a response to the two reply posts...
By 'flicker', I'm talking about the horizontal ghost bands that move up and down the image as you watch 18 fps 8 mm footage filmed at a non-matching speed. When you use ML film at a speed other than the standard (24/25/29.976/30 etc. fps) you are still shooting on the background of that standard speed. So g3gg0 is quite right. The camera records the file and plays it back at the standard speed, not at the speed you set for filming. That's why the use of slower frame rates in ML is really intended for achieving time lapse effects: when you play back, things are sped up.
I happen to be using 24 fps as the camera set speed. If I play back the 18 fps footage as shot, it's sped up by a factor of 1.33-fold. So I edit everything with Adobe Premiere Pro and adjust the speed of each clip to 75% (=18/24). Premiere then slows everything back to the equivalent of its original shooting speed but the use of 18 on 24 in the camera has eliminated the flickering bands. If you don't have editing software that can change the digital frame rate your footage will indeed look sped up.
I've now copied a lot of my old 8 mm movies. At one stage the flicker reappeared and I discovered by experimentation that was because the projector had suddenly decided to run a tad faster. Thanks to ML (and some patience and some cussing) I was able to restart copying at 18.62 fps. (Then I reset the clip speeds to 77.6% in Premiere Pro!)
Some years back I paid for a couple of professionally made copies from super 8 and was far from pleased with the results. They were mostly flicker-free (though it reared its head in places) but poorly lit. This is a definite limitation with copying: you need a projector with a strong lamp or you're unlikely to get a bright result.
While I remain mostly pleased with the results I've got, I have one problem to overcome. When the film shows something moving fast the 24 to 18 frame rate correction in Premiere interpolates a kind of double exposure effect, picking up bits of neighbouring frames to compensate for the slowing down process. It seems to do this whether a clip is or is not marked for 'frame blend'. If anybody knows a way to get the 18-on-24 footage slowed down without interpolation, please shout!
The 'ghost motion' effect created by software frame interpolation is something I find much easier to live with than the horizontal band flickering. I've uploaded to YouTube a short sequence of old movie filmed in a zoo so you can see the final product at
(I haven't cropped the film properly; that's not the issue.) The ghosting effect is apparent in a few places, but in general I'd say this result is almost as good as the best you can get with computer driven frame-by-frame copying using complex pulldown algorithms to match the speeds.