I am accustomed to using Premiere to edit DV SD Widescreen 16:9 from a canon XLH1 and on the same timeline editing AVCHD. Ppro sees this as 720x480 1.21. I just simply reduced the scale of the AVCHD and it worked great till Vista & Windows 7. When Ppro was dependable, this workflow gave me a DVD that would look well on 4:3 and then would fill 16:9 on a widescreen on Widescreen TVs. Now, in FCP6, I have captured the XLH1 as anamorphic 16:9 (as there is no widescreen setting) and am having difficulty getting clean AVCHD imported without getting interlace in the final. So I resorted to a 3rd party converter. The converter is working but I have to convert to 1280x720 to make it match on the timeline and output. Did Ppro look at 16:9 differently than FCP? Can you tell me what I am missing here? I need a workflow that makes a DVD that works well for 4:3 tvs and widescreen, all in SD.
Firstly in SD 16:9 is created by either anamorphic squeeze or letterboxing. Anamorphic is preferable as letterboxing simply uses about 65% of the frame so you are dropping resolution. So anamorphic is the correct widescreen option.
Secondly field dominance in DV is lower and in HD formats it is upper. Chances are you are simply getting a field order problem which can be corrected by applying the shift fields filter. Normally FCP does this automatically when you edit in material with a different field order.
Perhaps in the way you are converting the footage, you are baking in a field order problem.