Just slide forward to switch on and go brighter, and slider back to go dimer and switch off.
Either a slider or rotary switch with a detent at off position would do the job nicely. I wonder why the big brands don’t make such models 
Most simplistic UI is a switch that goes on/off.
Also, you always know whether it is at 100% or 0% for certain.
Simplest UI with multi brightness level adjustment 
But the switch can adjust between 0 or 100% 
Regular flashlights can adjust with 0, 20, 80, 100% or whatever, a regular switch is a single mode brightness adjustment.
Sliders are used with magnetic hall sensors
The problem with those is that they have a very high parasitic drain
So if you forget to turn off the light it will depleet the battery
I think there was a Jetbeam light which had a rotary brightness adjust with magnetic sensors, additional when the rotary was turned in the off position a small switch was pressed and the power to the magnetic sensors and driver interrupted
There are Imalent lights that use a rotary adjustment in the Tailcaps using a potentiometer which is seaked for water tighteness
One of their lights I have reviewed here
Yes, I think a 2-dimensional switch like a sliding or rotary switch makes for an effective and intuitive UI. It’s quick to get to any brightness you want. It has a nice analog feel to it. However, you generally don’t know the exact power level you are in so is not best for every application.
This has recently been an interest of mine. See my sliding switch mod here. I’m currently making a rotary switch in the tail of an S2 triple.
I may help you with your rotary S2 triple
I got here a defective Imalent light
The tailcap fits the S2+ body, just the tube needs to be shortened 2mm so the tail cap gets over the oring
When the replacement light arrives here I can send you that tail cap
Hey thanks Lexel, I appreciate the offer, but I just finished a prototype of mine and I think it will work pretty well.
Do you know how that imalent one works? Mine uses a supercapacitor to power the MOSFET gate.
Rotary like the Jetbeam RRT01 is wonderful. Also really like the Nitecore pistons like D10 and EX10, hold to ramp, release when it’s at the level you want. Of course, HDS Rotary is great and I’m eagerly awaiting Toykeeper’s Crescendo (sounds like a classical movement)
@EasyB, your prototype looks absolutely amazing. I wonder if any manufacturer is willing to make them, I’ll definitely be interested
check my review
I didnt concluded how it exactly works, but if you are willing to find out i can send you a dead driver
My guess is due to the low bleeder resistor of 34 Ohms it uses a very short off in full PWM to store energy in a inductor on the tailcap driver
Of course that will mean on max brightness the bleeder eats about 130mA when the LED is turned on
Thanks! I guess there are a few lights around that use a similar UI, they just use more complicated drivers than my mod.
It’s certainly an option and has been done to greater or lesser degrees in the past.
Issues are:
-maybe more complex to build, i.e. more cost.
-driver needs ramping modes. And many are PWM reliant for this.
-One handed operation may be hampered by switch layout.
-Accidental activation.
-No ability to activate in High, even if getting from low to high is pretty quick.
Difficult to access other modes or mode functions such as beacon or SOS and no ability to manually perform Morse Code.
Obviously there are benefits too as you mention.
I imagine IP ratings will suffer
Many diving lights got a slider
Its magnetic, so absolutely watertight.
I have never cared for side switches on my lights. I very much prefer the simple tail light clickie.
idk if it is the best for everyone, but it is pretty simple, i build few lights, with rotary control, but i went even farther, i used pot with switch function, some have off click on one side, whether it is on min side or max side depends where you solder wires, other pots have pull out on, push in off. (like lighting switches in old cars), as well as rotary dimming control. but those switches are pretty big, almost impossible to use in classic tube lights, but very handy in lantern\searchlight form.