Exporting black and white images

Hi,

	I produced the attached black and white map in R using following  
set of commands.

par(mfrow=c(1,2))
plot(Z.pop, main = "Mp",col = gray(seq(0.0,1,0.01)))
contour(sk.pop, add=TRUE, nlev = 6, col = gray(1))
plot(Z1.vmt, main = "Mv",col = gray(seq(0.0,1,0.01)))
contour(sk1.vmt, add=TRUE, nlev = 6, col = gray(1))

Z.pop <- as.im(stuff)  where stuff is a spatstat ppp file.


The attached black and white pdf file shown here, which was saved in  
R, gives a black and light gray grid-like pattern that doesn't exist.
The attached map will not produce this image in Adode Acrobat  
Reader. It can be opened in Preview.

A black and white map looks great in R. These issues do not exist  
when "col = heat.color", etc. i.e. a color palette. In fact, Adode  
Acrobat Reader opens the file without a problem. It suggests to me  
that the black and white map is corrupted.

A method to solve this problem would be greatly appreciated.


Thanks

Paul




<vmt2_9_BW.pdf>