Facebook has released its new facebook photo viewer just a while ago and has not appealed much to its audience. The new facebook viewer with black background has been little sluggish in opening and closing and I personally prefer the old viewer over this fancy new one.
After digging for a while on the internet I found these two methods to revert back to the old classic photo viewer.
1. This is a simple method and works on any browser any time. Just refresh the page(or pres F5) when you're viewing a photo album. The page will reload and there it is, the old and beautiful classic photo viewer. Sad thing is that you have to this for every album(not every photo).
2. This second method is more simpler because you don't have to refresh the page every time, but this trick works only on your Chrome Browser. It is a free extension that you have to install on to your chrome. It is called "Revert Facebook Photo Viewer" extension which is available in the webstore. Just install this once and you have to never worry about it again. The extension works in your background silently never showing you the new photo viewer of your facebook.
Both the tricks are working perfectly as of now. Hope this has been helpful to you.