Well, I found a million copies of diagrams stating 100ohm resistors for the LED backlight on my l2014 4x20 screen. Assembled it, checks, sod all backlight. Drops in a 47ohm instead. Bit better but not much.
So I spent a while tracking down the datasheet for my module - it claims 4.1v and 320mA typical. That all boils down to a 3.4 ohm resistor in line with the 5.15v supply. Now I tried shorting the resistor for a fraction of a second when I was running with 47 ohm one, and the brightness change was very significant. I've not tried the 3ohm yet, but I was considering sticking with a 5ohm one, this reduces the current to about 220mA.

If the units datasheet says 320mA, I presume it is safe to run that, but are there any benefits/pitfalls related to running less, apart from visibility problems in the sun?? What do you guys run?

James