How do you handle photo file size limitations as phones now take pictures using more than 6M?
Allow uploads as large as the picture file size you believe your users will upload.
So basically set the upload file size limit to 8MB or even 10MB.
In the Control Panel > Attachments page, use the default settings for Image Quality.
With the UBB.threads default Image Quality settings, most of your user's 8MB images will be compressed and stored to about 200K - 1.5MB.
Here is a sample gallery regarding this:https://www.ubbcentral.com/forums/ubbthreads.php/galleries/258291/test-for-attachment-sizes
And a screenshot with additional samples, as post attachments.