1.0 reflection 255 rgb and 1.4-1.6 IOR
yes
1.0 reflection 255 rgb and CoronaColor map with Solid HDR color set to 0,02-0,06 in IOR map slo]"
0.66 Solid HDR ;)
IOR = 1 / IOR Map
IOR Map = 1 / IOR
1 / 1.5 = 0.66
1 / 0.66 = 1.5
IOR map is the way to go since you don't clamp the fresnel value. Too bad we need to do math, would be simpler to just load a .hdr/.exr with 1.5 value. But you know, why should 3D stuff ever be simple.
edit:
I just want to add.
Glossiness should take care of most of the fresnel changes. If you have to make big changes to the IOR map, it mostly means that you are compiling different materials into one single material. Try to split the materials up and blend them. Like "Pure Material", "Dirt", "Water" etc.
IOR map shines when you have to fake depth, like grass materials. Glossiness can't do that.
PBR is giving me sleepless nights
PBR should make your life easier.
Leave IOR at 1.3-1.5.
Control everything with Glossiness.
If you have to fake depth, use IOR map. If not, just leave it alone. (In most cases)
Split materials instead of compiling them into one.
Keep it simple and nice :)