As a photographer, it makes me cringe everytime I see poorly uploaded photos to Facebook, but what is even worse, is when a fellow photographer uploades incorrectly optimised images.
Honestly...as photographers we are the trend setters, people look to us as inspiration, and we should always be uploading the clearest possible images for our clients to view and ideally have them book us.
So how difficult is it? Its actually insanely easy, Lightroom makes it so simple, especially if you are batch exporting, or even just 1 or 2 images.
Once you have edited your images and you export them in the usual 'full res' you do for your clients, I generally select my favourites for Facebook, I then export these into a Facebook Folder. The first time you ever do this will take a minute or 2, everytime there after is literally like clicking 3 tick boxes.
So this is the set up (see screenshot below) this ONLY applies to the first time.
Go to the Image Sizing tab, tick the Resize to Fit box, choose the drop and select 'Long Edge', then enter '2048' by the pixels, this will ensure that the long edge is 2048 pixels.
Keep the resolution at 299 ppi.
Then the very next tab is Output Sharpening, tick the 'Sharpen For' box, select screen and change the Amount dropdown to 'High'.
Click export and everythings done, your image size is perfectly optimised.
What makes it so easy is when you are NOT exporting for Facebook just untick the boxes, and when you do want to export FOR Facebook, you just tick them again, none of the settings within that Tab changes.
* Remember to untick these tabs when exporting full res images for your clients.
** Always remember to post images from your Computer and NOT your phone, Facebook downscales images from a mobile device a lot more than a PC.