What about DPI when sizing to 2048 the long way? Mine are usually 300dpi but since FB (FaceBook) changes that to 72 dpi, would I be better off to change to 72 dpi myself before uploading? Thank you!
It makes absolutely no difference for web viewing. 2048 pixels is 2048 pixels. Viewing apps will resize to whatever they resize to anyway.
For more about why it doesn't make any difference, please see: Is there any practical difference between saving at 300ppi or 72ppi?
As far as facebook specifically is concerned, facebook strips all of the metadata from your file anyway. Facebook also resizes, re-compresses, etc. images as well. The way to optimize images for facebook is to upload them at the exact resolutions for their intended usage and compress them yourself so that the total file size is less than 100KB. Other wise facebook will compress them further.
The value that Facebook sticks into the dpi field does not matter. Facebook has specific sizes they want to display based on photo width, and maximum file size. Their manipulation of the photo is based on those quantities, not the dpi. I have seen 96dpi and 180 dpi on Facebook images. It is all about the number of pixels and the quality of each pixel, nothing else. If you are worried about changes in quality caused by Facebook, then worry about the parameters that Facebook looks at. If you do not want them resizing, then hit one of those pixel widths. (after looking at a few images on Facebook, that parameter might be the maximum dimension, which can be either width or height) If you do not want re-compression, also make sure the files size is small enough. Note: these are always subject to change and the Facebook algorithm might not be perfect in what they do with images. Here is what Facebook says on their help pages ( https://www.facebook.com/help/266520536764594 ):
How can I make sure that my photos display in the highest possible quality?
We automatically resize and format your photos when you upload them to Facebook. To help make sure your photos appear in the highest possible quality, try these tips:
Resize your photo to one of the following supported sizes:
Regular photos: 720px, 960px or 2048px wide
Cover photos: 851px by 315px
To avoid compression when you upload your cover photo, make sure the file size is less than 100KB
Save your image as a JPEG with an sRGB color profile
You can also changes your settings so that your photos are uploaded in HD by default.
There also is a fairly recent "Photo Taco" podcast about this very same issue talking about various social media dealings with photos, including facebook, Instagram, and others. ( http://improvephotography.com/43150/photo-taco-sizing-sharing/ ) He is particular about doing what results in the best images and talks about his experiences.
The show used to run about 5 minutes or so, but recently it is averaging over a half hour. You can listen to it online or download the podcast.