Hi Stan,
Many thanks for your advice. I will attach the Sequence Settings for the video file created as advised. I'm wondering if I'm trying to do the 'impossible' by combining still and video images from both the IPhone and Nikon camera on the one Timeline? To put the video file on the Timeline I think I need the 16:9 ratio and not 4:3 that appears to be the default setting.
Malcolm
That's good now. That's what I was trying to get to. So, add your photo now to this timeline. Then you can adust the Scale setting in the Effect Control Panel. And have black bars left or right / top or bottom. Or you can scale the image so it fits into the frame fully, but you'll be cropping sides or top/bottom.
It's the way it works when you have different aspect ratios. People deal with this all the time, it's part of being an editor.