Changing the range with a IR emitter

Hey guys, I'm new here, and I'd like to ask you if anybody knows how to change the distance of detection with a IR Emitter, actually, I'd like to decrease it, I know that I have to place some resistors, so, If I change the voltage or the value of the resistor, this will have consequences in the distance detection, right, I'd like to know just an example or a quick schematic to see it. Thanks guys.

anfedres.... Just put increasing numbers of very thin paper in front of the emitter (think thin tracing paper)

Sometimes answers are easier than they appear.

If the tracing paper isn't acceptable, look for a series resistor on the IR emitter and increase the value a good 10 times or so. Like if it's 4.7Ω, make it 47Ω.