This is a Firefly IDL render, with the window's material set to ambient = 1

The apparent brightness of the window is correct, but it isn't casting enough light proportionate to that apparent brightness.

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Then I set the window ambient to 8:

Now the window casts light, but the hyper-ambient burns out the window image.

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Now, I use an unseen IDL emitter. The window is set to ambient = 1, so its apparent brightness is correct, and the emitter (ambient value of 7) produces the stronger lightcasting proportional to the window's apparent brightness.

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This is the properties settings for the window's emitter; un-tick the two highlighted boxes:

Firefly render settings:

This emitter trick isn't needed if you use Superfly; I can just set the material of the window itself to cast light in whatever strength I want.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5