Originally Posted by niznai

That would be lame, but I regret to say, it may be true.
Think of it this way.
An exponential is a function that varies very little around 0 (zero=rest or neutral position) and a lot at extreme values (an example is y=e^x) whereas a logarithmic function varies a lot around 0 and very little at higher values (y=lnx).

Some radios (and manuals) will talk about and display "exp", others "ln". These I suppose are short for "exponential" and "logarithmic" (or they should be). Both will scroll from negative (-100%) to positive (+100%) values, meaning probably that say a radio with "exp" applies an exponential response curve when values are positive (say +10%) and a logarithmic response curve when values are negative (say -10%). Of course, when the value is zero, the response wil be linear. The response curves are in reverse of course when the radio talks about "ln". I think this is where the feeling that different radios interpret differently "positive" and "negative" (exponential) comes from.

Clear as mud?