iMovie export file size. Which one I should use.

When you export out at Best Quality (pro res) you are exporting at a much higher bitrate than if you exported out at Mp4. So the pro res would be better quality than the Mp4. It might not even be noticeable except to the most discerning eye.

If you shoot the video in Mp4 it will be fairly highly compressed. iMovie unpacks it for editing purposes. Then if you export it out in the pro res format, you will release a lot of that compression, have more independent frames and fewer referenced frames, and get more detail and less artifacts. If you export it out at Mp4 with the same resolution as the video was recorded it should have the same quality as the Mp4 that you imported into iMovie. I have never been able to tell the difference with pro res versus Mp4 when watching on my computer. I just go with Mp4, as it is probably the most compatible viewing format.

-- Rich

Hi,

You probably will find it satisfactory for most purposes to export at High Quality, Better Quality Compression, and resolution as high or only one level higher than the original resolution.

If you export at Best Quality (pro res) you will get the best quality but it will be a .mov file at 4x the file size. Exports at all other quality settings will give you a smaller .Mp4 file.

If you will be posting on a website perhaps a lower quality small file size would be more satisfactory. On the other hand, if you intend to display the video on a large screen TV you might want the best quality that your TV can play.

What is satisfactory quality is primarily in the eye of the beholder.

-- Rich