Would it be acceptable to store some original images as PSD (i.e. PhotoShop) formatted files?
The standards guidelines advise against using a proprietary format, which this is, unless you have a very good reason to do so. Photoshop is perfectly capable of saving files in the TIFF format so you would need to justify why there is any benefit in storing archival images in PSD. That’s not to say, of course, that you can’t take a copy from an archival TIFF and store it in PSD to work on. Try to create a ‘master file’ in a format that can be re-digitised from easily.
