Original Image: Comparison Set:
Conclusion:The best iPhone Flickr Upload App is the Mail App using the Copy and Paste Function! (How to use Mail App here)
Reason: Due to Apple OS restrictions, all Third-Party Apps are not allowed to have full access on Files, that means, any third-party App doesn't have permission to read the Date Taken info or Geotag info, even the original File size the picture taken with can't be retrieved.
Goodbye to all Third-party Flickr Uploaders!!
Hint: To use the Mail App, you have to setup up a Flickr E-mail Adress here