Change resolution permanently before taking photos

I want to change the resolution permanently before taking any and all future photos to save iCloud space. I know about keeping the smaller versions, but that's not what I want to do.

When I email a photo, I'm posed with four resolutions to choose from. I don't want to send a 1 - 2MB or more photo. I'd like them all to be good for websites.

I want to reduce the resolution for both my iPhone 6 and my iPad mini 3.