The scene below renders much brighter when you turn focal blur on (set blur
to 1), and I'm sure it shouldn't.  Does anyone know the cause?  Here is all
the information I can muster:
Computer:  Pentium Pro 200, 32Mb ram
OS:  Windows 98 and RedHat Linux 6.0 running GNOME and Enlightenment
POV distribution:  Version 3.1g.msvc.win32 [Pentium II optimized] and
generic Unix 3.1g built from source to x-povray.
Other notes:
assumed_gamma and ambient_light do not seem to be the cause.
The specific settings of the focal blur do not seem to be the cause, but I'm
still not ruling out a problem with my scene file.
There is a gamma correction made at the end of the focal blur function in
the Unix source (I assume it is there in all the distributions), when you
remove this gamma correction, the scene seems to render appropriately, but
this may simply be breaking one thing to cover over another and may not work
in all circumstances (untested).
A bug with the gamma correction of focal blur was apparently fixed in 3.1b,
but I don't have the previous sources handy, so I can't compare them.

So, what's the verdict?  Any help will be greatly appreciated, thanks.

This is the test scene:
#version 3.1;

global_settings
{
  assumed_gamma 1.000
  ambient_light 1.000
}

#declare blur = 0;

camera
{
  location  < 0.000, 0.500,-1.000>
  look_at   < 0.000, 0.000, 0.000>
  #if(blur=1)
    aperture 0.100
    blur_samples 7
    focal_point < 0.000, 0.000, 0.000>
    confidence 0.900
    variance 1/128
  #end
}

light_source
{
  <-3.000, 2.500,-2.000>
  color < 1.000, 1.000, 1.000>
}

sphere
{
  < 0.000, 0.000, 0.000>, 0.200
  texture
  {
    pigment
    {
      colour < 1, 1, 1>
    }
  }
}

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