The video in my timeline is 720 by 480 (1.2121). When I clip on "Export Frame" in the program window it exports a jpg that is 720 by 480 (0.9091)
I know I can right click on it and "modify - Interpret footage" and correct the pixel aspect ratio.
My question is "Why is it doing this and how can I correct it"?
Is their a setting I'm missing? Why does it change the pixel aspect ratio?
Your timeline has rectangular pixels, a jpeg has square pixels.
If you want a jpeg with the correct view (no squished persons etc) you need to export it to 864x480.
The jpeg is not square. The pixel aspect ratio would be 1 and not .9091, if it were.
I have two computers. On one the "Export Frame" exports the jpeg with the same pixel aspect ratio.
The other machine changes the pixel aspect ratio from 1.2121 to .9091.
I can't find any differences in my settings.