This is how you can get identical images with or without mia_exposure_photographic node as lens shader. In this case you are able to set typical light values witch you are usually use.
Cm 2 Factor: 1*
Film Iso: 1000000 (This is the main cheat)*
Camera Shutter: 100
F Number: 10.5
Burn Highlights: 1
Crush Blacks: 0
Gamma: 1 (Super important!!!!!)
One more tip for the Physical Sun and Sky system:
Use this values inside the mia_physicalsky node for physically accurate lights:
R Unit Conversion: 0
G Unit Conversion: 0
B Unit Conversion: 0
The unit conversation equal 0 is a special built in value.
Means: “For convenience, the special rgb_unit_conversion value of 0 0 0 is internally set so that 80000 lux (approximately the amount of light on a sunny day) equals the classical light level of 1.0.”
* Or you can use 10000 as cm2 and 100 as ISO.