The IDL emitter will have very high ambient value, so it would appear as basically a flat white silhouette.  The trick is to conceal the emitter.  In P9 and later, you can simply un-tick the visible in camera box (and also casts shadows box) in the properties tab of the prop's parameters panel.

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     If you have another mesh surrounding the emitter, that object will need to have casts shadows un-ticked, or it will block the light.

     Bear in mind that the emitter will cast only diffuse light;  for best render results, I prefer to use both an IDL emitter mesh and either a point or spot light.  The Poser light will provide specular highlights which an IDL emitter prop lacks.  The IDL emitter provides a more realistic distribution of light than the poser light.

     If you make a candle, give the wax considerable SSS, so that it has some translucence.

edit:  cross-posted with hborre! :P

Poser 12, Poser 13, Poser 14, in feet.  

OSes:  Win7Prox64, Win7Ultx64, Win11

Silo Pro 2.5.6 64bit, Silo 2025.1, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5