The HDR-FX7 (prosumer) and the HVR-V1 ("pro") are "siblings". They have a 62mm filter diameter lens and 1/4" 3CMOS imaging chip system.
The HDR-FX1 (prosumer) and HVR-Z1 ("pro") are "siblings". They have a 72mm filter diameter lens and 1/3" 3CMOS imaging chip system. The FX1 and Z1 have essentially been discontinued.
As the lens system filter diameter gets larger and the imaging chip size increases, the low-light behavior improves. The HDR-FX1000 is the prosumer and the entry level pro is now the HVR-Z5.
I use an FX1 and like it a lot - even in low light. It *can* get grainy. If you want that eliminated, then you need to move out of this "low end" and into DVCPRO HD (Panasonic), HDCAM or XDCAM (Sony). Another option is to shoot in better light, then darken down when editing.
Actually, I have a couple requirements and am having difficulty tracking a camcorder down with all of them: good in low light, external mike input, manual focus (it can have automatic, but I need the manual option), HD, and a fire wire port. Help me out here, I've looked at a lot of Sony HDR-FX7s and HVR-Z1U, but the problem I run into is poor lighting.

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