Thanks for the suggestion sooperFoX, but I'm not using area_light at all. 
Here's my light_source:

light_source
{
  <500,350,-100>
  color Light_Color
  spotlight
  radius 1
  falloff 2.5
  tightness 10
  point_at <0, 0, 15>
  photons
  {
    reflection on
    refraction on
  }
}

The wierd thing is this ONLY happens when I use a cone object. Nothing else 
causes it. FWIW, I've attached the final result of my tinkering. Some of the 
old-timers may recognize this from some previous experiments with photons. I 
just resurrected it in order to generate a 1920x1200 version for my new 
monitor desktop.

-- Dave

"sooperFoX" <bon### [at] gmailcom> wrote in message 
news:web.4700aae86a7782f5943b35b60@news.povray.org...
> Hi Dave,
>
> If you're using the area_light keyword *inside* the photons block of your
> light_source, that will cause artifacts in a lot of cases. Try disabling 
> it
> (you can leave it turned on in your native light_source for the soft
> shadows) and you should lose the speckles.
>
> Below is an excerpt from the pov-ray documentation (3.6.3.3 Photons FAQ,
> second-last question):
>
> "Photons do work with area lights. However, normally photon mapping 
> ignores
> all area light options and treats all light sources as point lights. If 
> you
> would like photon mapping to use your area light options, you must specify
> the "area_light" keyword within the photons { } block in your light
> source's code. Doing this will not increase the number of photons shot by
> the light source, but it might cause regular patterns to show up in the
> rendered caustics (possibly splotchiness)."
>
> The last sentence is of interest, I think.
>
>
> -- sooperFoX
>
> "NetDave" <new### [at] netdavecom> wrote:
>> Thanks for all the suggestions everyone. So far nothing has worked. I 
>> tried
>> a bunch of other objects and they all seem to work ok. I guess I'll come
>> back to this sometime, but for now the cone doesn't seem to want to
>> cooperate. Lots of other shapes will make this scene work and I'll post 
>> it
>> when I'm satisfied with the composition.
>>
>> -- Dave
>>
>> "NetDave" <new### [at] netdavecom> wrote in message
>> news:46edc6c0@news.povray.org...
>> > I'm sure this is a frequent problem, but I just can't find the 
>> > information
>> > in the documentation. I'm rendering this scene with photons and as you 
>> > can
>> > see in the attached image the returning rays through the cone are 
>> > coming
>> > back as speckles. I've tried some of the photon settings with no 
>> > success.
>> > Thanks for any suggestions.
>> >
>> > -- Dave
>
>
>
>

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