Complete newb here; sorry this may be a basic question but trying to learn. I made a simple circuit with nothing except an Arduino power source a 100 Ohm resistor in series with a 10mm red LED. Weirdly it gets dimmer if I remove the resistor and my question is why is that occurring? I thought reducing resistors would brighten the LED. The datasheet is attached. The max current is 80mA and the LED worked fine after and this phenomena is repeatable so I don't think I burned the LED out. This phenomena doesn't happen if the power source is 3.3V in which case I don't notice much brightness difference between the two. This phenomena also doesn't occur with a same sized blue LED by the same manufacturer. FYI, there's no code, I am running the power direct from the Arduino Uno's 5V and 3.3V pin and gnd pin. I read the Sparkfun tutorial on resistors and am confused.