Originally posted by cats_five Where on the web are you using it? 1200 pixels is rather wide for a lot of screens (especially since a lot of us don't run the browser in full screen mode) - 1024 or even 800 is more user-friendly for a lot of people.
My own assumption is that it is going to be resized again (automatically) on upload. Works that way for most major photo sharing sites. Back when I tried to manage my own site, I also generated versions in various smaller sizes still, including thumbs. But I still like starting with a 1200x1800 for my own usage. I call them "proofs". Big enough to view full screen and then some, big enough to generate 4x6 prints at 300dpi, more than big enough for web use (again, I assume it will be downsized automatically, and it is on all sites I use), but small enough I can reasonably keep proofs for all my keepers (say, 50% of my images) on my laptop harddrive forever. For most images, this 1200x1800 proof is the only copy of the image I'll ever need to access regularly. The original PEF can be safely archived away, as could any full size derivatives (TIFF, etc) that I might have needed to generate during the editing process.