Hi Irene,
When I re-read my answer I realized it was too long, so I’ll sum it up quickly: Use Sony Catalyst Browse to create ProRes files, and keep editing in FCP7.
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Here is the too-lengthy answer:
Premiere is great and will work fine with your camera originals. It requires a subscription, but if you already have it available, you will enjoy it.
You could also try editing with Resolve 12 (basic version free), if the learning curve doesn’t bother you. It’s very much like FCP 7.
If you want to keep using FCP7: You could use a file conversion program to create ProRes files, which work directly in FCP 7 on Yosemite. I’ve tried three file conversion programs: EditReady, Wonder- Share Video Converter Ultimate, and Sony Catalyst Browse. There is also Sony Catalyst Prepare, which I haven’t used. They’re all different; look for reviews and enjoy!
My favorite is the free Catalyst Browse. It will do some color correction and is pretty fast. I think it might lack file checksumming??? So if I were in the field, copying SxS cards off to a hard drive so I could recycle the SxS cards for the next shoot, I’d use something else like Sony’s old Content Browser or Imagine Software’s ShotPutPro, to copy the BPAV folders to one or more hard drives first.
(The only caveat I have about my experience: I did some of the test conversions with an older MacBook Pro running 10.8.something. But I used Browse on a Yosemite MBPro.)
Please let us know whether this works for you.
Bob C