it's been a while :V

Somewhere between 5 and 10 years, aye. x_x

If you upload an image that is larger than 1280 pixels on any side, FA will resize it to that. A workaround is to use the 'update source file' link (it's below the "See More" panel as you're looking at this page) to re-upload the larger image. The size check is not performed the second time around.

Also know that the current UI resizes images to fit your monitor regardless of original resolution. Using the 'Download' button will show the image without that adjustment. Or you can switch your user settings to always display the non-fitted image by default when you click on it