Here are some considerations about photons I'd like to share.

  The left image is the normal render you get with one light source.  In
my 
opinion, the dark shadows cast by the glass are to dark.  I have
observed 
this kind of refractive caustics in some experiments I have done with
real 
glasses and lights, so they are right from the physical point of view as 
remarked by N. Kopp elsewhere in this newsgroups.  In the other hand,
the 
reflective caustics are to bright.

  One extreme solution to both is to shut down photons all together.  We
all 
know that in most scenes this is a bad solution.  There is an
intermediate 
solution.  Turn on a second light source (in the same position off the 
original one) with reflection and refraction off.  The result is shown
in 
the right image.  The light that shoots photons has rgb .12 and the new 
one, rgb .88 (this settings may not be the best ones).  The rendering
time 
of the two images are more ore less the same.  The slowing down due to
the 
two lights is partially compensated by less sampling needed in anti-aliasing.

  BTW, here are the settings for the glass:

pigment{rgbf <.94, .94, .94, 1>}
finish {ambient 0  diffuse .5  reflection 0.065  specular 1  roughness .005}
interior{ior 1.5  media{absorption <1, .75, 1>  density{rgb .01}}}
photons{target 1  reflection on  refraction on  ignore_photons}

They work well with  global_settings{adc_bailout .05  max_trace_level 100}.

  Finally, this are only my opinions and you may have other ideas/solutions.

  Alberto.

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