Well, Firefly's IDL was intended to account for passive bouncing of light.  To simulate  things which are active light emitters, you need to fudge a bit.  Thus, one mesh for the visible prop, which will have only a gentle ambient (half, two-thirds, at most 1) so that the visible prop retains a realistic color and allows a perception of shape and depth.  If you give the visible prop too high of an ambient, (5, or 20, etc) then the prop flattens out as a white silhouette.

     That is why I use a separate -and unseen by camera- IDL emitter.  The emitter prop can have an ambient of 5, or 50, whatever is needed to effectively cast light.  The greater the surface area of the emitter, the lower the ambient intensity needed, and the less splotchiness for a given render setting.  Rendering with gamma correction will also tend to lighten and even out the lighting in a scene, so I'd recommend that you start using it.

     For your lamp, I would use a high-ambient bulb emitter that is perhaps twice the diameter of the visible bulb, and a low-ambient emitter closely fitted around the lampshade, since lampshades are generally somewhat translucent -not opaque- and so the shade should give a little light also.

     All of this extra unseen mesh nonsense complements the point light by casting light from a volume.  A lightbulb in a translucent lampshade doesn't cast light from a single point, does it?  No, it casts light from the filament, the entire surface of the bulb, and -more gently- from the surface of the lampshade.

     If you use only a point light, the shadows will be grossly unnatural.  If you use only concealed IDL emitter meshes, the light will be dull, lacking specular highlights.  Use both.   Concealed IDL meshes combined with Poser lights have synergy, symbiosis, ...something like that.  They each compensate for the weak points of the other.   Bring the full arsenal of Poser lighting to bear, and the total effect will be greater than either of the components used alone.

Ye olde medieval wall torch example:

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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