Despite selecting the High option when exporting JPEG images from Photo, I am finding the file size at destination is around 3MB - 60% smaller than when I exported the same images from iPhoto with the High option. Image size is unaffected. If Photo is compressing JPEG images more during export than iPhoto, I fear the image quality is also being reduced. Is this correct?
There is a possibility that Photo is actually extra-compressing images at the import stage, not during export. Or both!