It doesn't appear to be able to change the file size for jpeg pictures. This is most annoying as I can't send multiple pictures via e email. Had to download a third party app, open cam, on order to do this. Poor performance.
@SteveSmith: Sorry to hear of your disappointment. You may wish to try opening the Camera app > Tap the cog symbol in the top right > Save options > Enable HEIF Pictures. This will convert images into high efficiency files, reducing the file size. Hope this helps.