Scaling factor applied to HDRI pixel values?

[豪三品8170]

Hello,

I am trying to export 3ds Max scenes to a proprietary PBR engine using MAXScript and/or the SDK. My question is, is there any way to get the scaling factor, which seems to be applied to the pixel values of HDRI used as an environment map?

The following is an example scene setting (no objects, environment map only):

The environment map has pixel values around 14 cd/m^2 in the red circle as follows: 

And, the followings are the images rendered with the ART renderer:

Luminance distribution (with Pseudo Color Exposure Control)RGB image (with Physical Camera Exposure Control) 

As you can see in the left image above, the luminance values in the red circle (corresponds to the environment map) seem to be scaled by some value around 500. So again my question is, is there any way to get this scaling factor using MAXScript and/or the SDK?

Any hints would be greatly appreciated,

tmishina