What version of Poser are you talking about? FireFly's shadow map temp files are in the same format as those of Pixels:3D, you can even re-use shadow maps that Poser created when rendering in Pixels:3D. The interlacing effect you see comes most likely from the fact that shadow depth maps usually are rendered in 32 bits/pixel where I assume that Photoshop opens raw files only with 8 or 16 bit per pixel - effectively stretching one pixel in the shadow map over 2 or 4 pixels in Photoshop.