I posted Google this question to usenet (google groups)
How much quality is lost when a @1998 SONY Hi8 analog camcorder transfers Hi8 output with a high-quality (Monster $40) RCA (video composite, 2 audio) to a mini-video jack cable VERSUS using a high quality S-video cable with a separate audio-only RCA to mini-jack cable?
Here's the background if needed:
I have a @ 7 yo SONY analog Hi-8 camcorder with S-video I/O. I just bought a Canon Elura 90. I have 30 days to return the Elura if I want something else.
Here's the problem. The 2005 Elura 90s don't have S-video input/output . They use an all-in-one mini-jack connector for analog I/O -- similar to what digital cameras use.
One of the main things I want the Elura to do is reasonably high quality conversion of my legacy Hi-8 tapes to digital format. I'll then edit the digital tapes over time on my purchase-pending G5 iMac and burn DVDs to archive.
 Instead they have a still camera capability. Arghh.
I've been told that if you're going from 8MM (or, shudder, VHS) to Mini DV the signal degradation impact of the composite video connection (mini-Video jack aka Video mini-jack to RCA plug composite) isn't that great. The source material is crummy to begin with.
Hi8, though, is a much higher quality source. It has 80% of the resolution of a mini DV digital capture. My experts tell me that the composite video has a significant impact in this setting.
The best solution would be the analog 3 channel RGB to analog 3 channel RGB input. That would require a professional level Hi8 camera and a pro level digital video camera. Next best is S-video, which is what I'll be getting.
I bought the camera from a high-service vendor so they didn't blink when I explained I wanted to swap out for the Optura 50 which does have S-video analog I/O.