Just compress the file. Your photo editor will have a tool to compress the image and make the file smaller.
It does seem so easy to post the file straight out of the camera, but it is often a big file and and even if it does work, consider compressing the file. The UU platform is like a big database, if we load TerraBits of photo files it is going to eventually slow down the database. There is no real need to post a photo which takes up the whole screen on UU, it is actually an inconvenience for many of us because it blocks the entire screen and instead of seeing four or five posts, all we can see is wood.