[Radiance-general] Horizontal artifacts in large image

[Mark Stock]

Fellow Radiance users,

I recently completed a large image (1.4 GB .pic file, 16k
by 24k pixels), and it appears like there are two obvious
horizontal bands of incorrect values (one 30% from the top,
the other ~80% from the top). I pfilt'd the image down to
5% of it's original size to make the image below:

http://mark.technolope.org/image/p21c_fish_take_3/redo_smooth_6/timg10_1_tw.jpg

The commands that I ran were:

rpict -x 16000 -y 24000 -vta -vp 0.2 0.2 -0.01 -vd 0.454 0.891 -0.08
-vu 0 0 1 -vh 58.66667 -vv 88 -ab 1 -aa 0 -ad 16 -as 0 -dv -ds 0.1
-dj 1.0 -t 600 -o img10_1.pic real.oct

pfilt -1 -x /10 -y /10 -r 0.4 img10_1.pic > timg10_1_t.pic
pfilt -1 -e +3 -x /2 -y /2 timg10_1_t.pic | ra_ppm | cjpeg -q 95 > timg10_1_tw.jpg

Does anyone know where these artifacts originate, or how to
prevent them from appearing? I'm running the same image at
reduced resolution right now, but final print quality is
not going to be as I'd hoped.

Mark