My initial files are in RAW. When I was only using Photoshop Elements, I was always working in PSD format. Now I also have Lightroom. As recommended, I first do all the possible editing in Lightroom and, if needed, I afterward transfer the file from Lightroom to Photoshop Elements for further editing. Why would I then use, in PSE, the TIFF format instead of the PSD format? Lightroom permits both, but the default setting is TIFF.