When you send a photo to an external editor for editing, by default Lightroom automatically embeds the ProPhoto RGB color space into the photo. ProPhoto RGB is Lightroom’s native color space. It has a very wide color gamut, and in many ways it’s an ideal color space for today’s digital photographers. However, as soon as your photo arrives in Photoshop, unless you already have Photoshop’s working color space set to ProPhoto RGB, the Embedded Profile Mismatch dialog box appears (see Figure 6).
Ideally, you’d change Photoshop’s color space to ProPhoto RGB (in Photoshop’s Color Settings preferences) before your photo leaves Lightroom. However, you can convert the file to your working color space—hopefully Adobe RGB (1998) and not sRGB—by choosing Convert Document’s Colors to the Working Space in the Embedded Profile Mismatch dialog box.