Having to re-render is mostly a function of the power of your edit computer (and the codec you edit with). I can move images around in DVCProHD and get a green line, so I can play without re-rendering. You don’t mention what codec you’re using. If you were editing in 8-bit UC and switched to DVCPro50 you might not have to render as much.
John
MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.5 QT7.5.5 Kona 3 Dual Cinema 23 ATI Radeon HD 3870
ATTO ExpressSAS R380 RAID Adapter, PDE Enclosure with 8-drive 6TB RAID 5
24″ TV-Logic Monitor
Final Cut Studio 2 (up to date)
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