jvc250 or sony dsr NOT have 4:2:2 color sampling, only 4:2:0 in PAL mode
jvc have 1/3 matrix, DSR 2/3
if you have 4:2:2, try another way:
JVC on component port makes 1080i (or 720p) in 4:2:2 color space
of course on HD-SDI its same (SDI its digital componet)
i think, SONY DSR-450 have on SDI 4:2:2 sample rate
You have connect this camcorder to another recording device and record to external device
ideal its NANOFLASH device
but better quality (high chroma sampling) it some difficulty when you keying and cut blue screen (in this case – DV family better use green screen)
i have some camcorders and also JVC 201 and DSR-570 with wideangle lenses.
Sony (in SD modes of course) is better.