You can see exactly what ProPhoto RGB is and you can modify it to Melissa RGB (albeit with a simplifed gamma, not a 2.2 TRC) directly in Photoshop's Color Settings.
That is good to know. I had always mistakenly presumed that ProPhoto MUST be paired with a 1.8 gamma curve and Adobe RGB MUST be paired with a 2.2 gamma curve or something would go wrong. I want to use ProPhoto RGB 2.2 in Photoshop just to be consistent with Lighroom, which renders 2.2, as well as the Epson ABW print driver, which only feeds on 2.2 gamma images. So now I will.
