Tweaking lightmaps in photoshop

Hello, when unity generates a lightmap, it saves it in a 32-bit exr format.
I'm editing this lightmap in photoshop to add some more detail using ambient-occlusion and cavity maps (using multiply blending). After I save the tweaked lightmap in 32-bit EXR format, it doesn't look much different from the original lightmap, but once I apply it over to my terrain, the terrain gets like 10 times brighter than it was originally. Where does this difference come from and how can I reduce the brightness? Visually the unity-generated lightmap and the one I made in photoshop look the same.

Unity-generated lightmap:


Tweaked lightmap with ambient occlusion map added:


Terrain with unity-generated lightmap applied to it:


Terrain with my custom map applied to it:


What can I do to add all the ambient-occlusion detail and keep the same brightness?

Thanks!

 

Photoshop have some difficults with 32bits alpha... same issue with blend textures. Try to use GIMP

 

So what are my options to combine the maps correctly?

 

GIMP won't import the EXR lightmap...

 

Make sure your Texture Type is set to Lightmap. I felt like such an idiot when I realized the reason I got these same results was just because I hadn't set the new textures to Lightmap after making making changes to the original, saving as a copy, and using the copy in the lightmap array. I'm using Photoshop CC with the OpenEXR format. Works fine for me.