Photo resolution after using Markup - drops to much lower than original picture

It appears that the markup tool reduces the resolution of edited photos. How can I select to save edited photos in the original resolution?

I cannot find any settings in Photos or Camera that affect this. In all the cases I have checked, the image resolution and file size are lower after editing with Markup. I'd prefer not to lose image quality as a result of using Markup. Is there some way to maintain the original resolution when editing with Markup?

I use this for taking job site pictures and conveying information to others. Useless if you zoom in and just see big pixels.

Any help would be appreciated.