It's "Pixelpipe HD" that sends full resolution pictures to Dropbox, using Dropbox alone on my iPhone to upload photos wirelessly puts lower resolution or compressed pictures with smaller filesize in my Dropbox

"Pixelpipe HD" fixes this by sending full resolution pictures to my Dropbox.
Here is the top photo send with Pixelpipe HD to my Dropbox and the bottom photo is the same picture uploaded with Dropbox itself on my iPhone:

You can see the difference in file size for exactly the same picture.
(filename is different because Dropbox & Pixelpipe HD change the file names themselves while uploading)