Levels definition

[Salvador Calabria Montero <scalabri@xxxxxxxxxxxxxx>]

Hello all,

I know it has to be a very easy question, but I am wondering if it is 
possible to define a level that covers without fixating an upper limit.
For instance, in a shade command, Can I define a level that contains all 
values greater than 10.
I have not found it in the Ferret User's Guide.

Thank you for your help