OD LED Power Level vs resistor packs

Hi, so I’ve been looking at this and I’m slightly confused with what to do. Is there a way I can modify the setup I have right now (bought from you completely built) such that it is more sensitive at lower ODs?

What sensitivity are you trying to hit and for what application?

Hi, there!
If I’m starting a new experiment, how do I define which LED emission is ideal for each value, quantitatively? I know it depends on the range I’m trying to read but does it also depend on something else? Knowing the range I’ll be reading, how do I choose the LED emission?