Check out the images in p.b.i -- the image was generated with the
following code: (rander with +QR)

camera {location 2*y look_at 0}
light_source { 2*y rgb 1}
global_settings{
  assumed_gamma 1.0  // makes error more apparent
  radiosity{}        // comment this out to get correct image under
MegaPov
}

plane {
  y,0
  pigment {
    spherical // or cylindrical -- doesn't matter
    color_map {
      [0 rgb 0]
      [1 rgb .05]
    }
  }
}

Take out the radiosity{} block, and it renders "correctly."  It does
this no matter what where the camera or light source is.  It renders
correctly under both Superpatch and plain ole' 3.1  All that is
happening is that the outer edge is being brightened more than it should
-- and, interestingly enough, the distance inwards that this ring
reaches is inversely proportional to the brightness of the center spot. 
The brighter the central spot, the smaller the area affected.  Anyone
ever seen this before, or have a clue what's causing it?
-Alex V.

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| Take out the radiosity{} block, and it renders "correctly."  It does
| this no matter what where the camera or light source is.  It renders
| correctly under both Superpatch and plain ole' 3.1  All that is
| happening is that the outer edge is being brightened more than it should
| -- and, interestingly enough, the distance inwards that this ring
| reaches is inversely proportional to the brightness of the center spot.
| The brighter the central spot, the smaller the area affected.  Anyone
| ever seen this before, or have a clue what's causing it?

Seems a numerical problem relating to color maps but nothing I know about to
begin with.
I gave your test a try and found that the bad effect disappears at around
0.015 (640x480 res) for the index 1 color.  I changed gamma downward to 0.5
or 0.1 to get a much better look at it too.
Increasing the index 1 color to 10 seems to make it disappear once again but
I couldn't say for sure it does altogether, it simply moves the "ring"
outward more and more as the rgb is increased.
Anyway, it's certainly a color map number thing and however it relates to
radiosity.  So you're not the only one seeing the problem.

Bob

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