[Radiance-general] macbethcal error

[Rob Guglielmetti]

Howdy.

So, I'm trying to use the macbethcal utility for the first time, and am 
getting an odd error.  The first time I tried to create a calibration 
file I got an "out of gamut" error, which I understand points to a 
poorly exposed gretag photo.  Before re-photographing everything, I 
thought maybe cropping my gretag image to the registration marks may 
help (lazy Sunday thinking).  But now, after cropping the photo and 
re-creating the pic file, I now get the following error when running 
macbethcal (macbethcal -d debug.pic mbscan.pic colorcal.cal):

macbethcal: non-increasing neutral patch

The resulting debug.pic is 59 bytes and is useless.  Two questions: how 
can I get a better image to avoid the out of gamut error, and what 
caused the error above?  I was using northern skylight on a fairly 
cloudless day for my lighting, and f2.0 1/125 for all exposures.