I am having a problem with substance painter that is driving me crazy and I cannot seem to find a solution. If I create a roughness layer and set the greyscale vale to 0.08 when I export it as a PNG and import it to photoshop the greyscale value is 0.11 which means I get a completly different roughness to the material and not what I have chosen in Substance Painter.
How can I solve this. The color profile for roughness is set to L8 and I export using 16 bit PNG.
Photoshop uses ICC colour management for both colour and grayscale documents. Substance Painter exports without a grayscale profile embeded. When you open your PNG in Photoshop, the document will be assigned an ICC color profile. Even if you choose 'don't color manage' the document will be treated as if it was in the current grey working space for display and when showing values in the info panel. You will notice in Photoshop's info panel that the gray K values are correct and are the inverse of the expected L value. To display the L value correctly you will need to assign an ICC profile to the document that uses a linear gray space. None of the included gray profiles do that.
You can search the internet for such a profile e.g. the Quad Tone RIP software includes a Gray Lab ICC profile that will give the correct L values in the info panel.