Further to that, I suggest wiring a small circuit up for a few pence that will allow you to adjust the brightness of the LED by adjusting the voltage applied using a variable resistor.
Depending on the voltage rating of your LED which is typically around 1.5 - 3 Volts I would apply a 1000 ohm (1k) resistor in series with a 0-10,000 ohm trim pot which gives you resistoe adjustment from 1000 to 11000 ohms which when I apllied a 6 volt supply to resulted in very prototypical light levels using DCC Concepts 1.8 mm panel dot typw Prototypical White LED.
Depending on the voltage rating of your LED which is typically around 1.5 - 3 Volts I would apply a 1000 ohm (1k) resistor in series with a 0-10,000 ohm trim pot which gives you resistoe adjustment from 1000 to 11000 ohms which when I apllied a 6 volt supply to resulted in very prototypical light levels using DCC Concepts 1.8 mm panel dot typw Prototypical White LED.