How to upload to Facebook from Photos?

I'm not impressed with the change to Photos. I used iPhoto on my MBP with few issues. Photos has doubled the size of my image library which is going to take some time to unravel (and I did set it up in the standard way - ie didn't change the default storage location so there should have been no duplication).

However, I have found that Photos will only contemplate uploading 50 images to Facebook. The facebook limit is 1,000 so the problem is not at their end. When I press the upload button in Photos, I am offered Facebook if I have 50 or less images highlighted but it disappears with no explanation if I have 51 or more.

Any ideas why this might be?