What is unacceptable to you for a flashlight

For me it’s proprietary batteries and/or non removable batteries.

I will not buy a light that falls in this category.

I second the above.

Also, hold for off

Agreed on the above.

Proprietary batteries, unreliable lights, lights that let water inside, and bad heat transfer.

Not a deal breaker but irksome.

Aahh

Thermal regulation that zigzags like this:

Or drops to near zero like this:

Both can be fixed with a couple lines of code in the driver, but they’re just lazy or don’t care.

I agree with the above, plus the turbo mode i think that isn’t that good except for some specific uses - cases - jobs, because it puts a lot of pressure - stress in general on the flashlight and battery !

In terms of UI - no shortcut to low, especially combined with mode memory. Also blinkies being a part of mode rotation again, especially combined with mode memory. I can live with hold for on/off, double click for on, whatever. It is a matter of getting used to. But when i can not know what mode i will have on power on and no way to avoid cycling through blinkies - that is unacceptable.

In terms of electronics - PWM (i know fast PWM is not really an issue, still i prefer to avoid it altogether), weird thermal regulation which tries to increase power back up once cooled resulting in wild brightness swings, no LVP (i do not want to have to think about that if i happen to use unprotected cells) and particularly cold emitters, like 6500-7000k.

Proprietary or built-in batteries are also a big disadvantage, but not strictly unacceptable. I am willing to live with it if it feels justified. What olight is doing with standard form-factor cells which are intentionally made incompatible for no good reason is unacceptable though.

As L37 says - Crappy PWM / duty cycle. I only put up with it on lights that get used for short times. Like the Nitecore TUBE where low is 500Hz (if I remember right). Above low it gets faster and is acceptable.

A UI that forces me to go through Hi, Med, Low just to turn the thing off.

Proprietary / non-removable batteries - except on specialty lights - like key-chain lights.

A switch that is so flush with the body and can’t be felt in the dark. A constantly lighted switch helps here.

USB port that is easier to find by feel that the main switch. Charging ports unless well covered - like with a twist off tail cap.
The pop-off kind are just another failure point for water to get in.

Turbo stepdown is OK if not too short. But high should be held for as long as the batts can sustain it.
All the Best,
Jeff

Dual (or more) switches. Nuh-uh.

There are a few things I consider important, some of them already mentioned by other posters above:

Non-programmable UI: a single UI with memory mode really doesn’t work for me.
UI should be programmable and include shortcuts to the highest and lowest brightness levels.
The flashlight design should allow for one-handed operation - e.g. not two switches in different areas of the body.

Integrated battery: an integrated battery that cannot be replaced is not an option.

Crenulation: I hate lights without any crenulation but avoid aggressive crenulations too (no use).

USB rubber cover: I don’t like rubber USB covers either though I don’t consider them a deal breaker if everything else is right.

Strobe: strobe is highly overrated - switches dedicated to strobe are a waste in my opinion.
Not a deal breaker if there is a UI setting that offers what I need.

PWM (pulse width modulation)… has to be the most unacceptable fault, IMHO. At this late stage of the game in LED flashlight technology? C’mon… even many cheap flashlights seem to avoid PWM. When I’d bought my RovyVon Aurora A8 for $55 shipped, I was so pissed off to find that noticeable PWM was evident. It took a couple of years, but finally RovyVon listened to the complaints and PWM was eliminated. A newer A5 purchase confirmed that.

I don’t mind a proprietary battery for less expensive lights. I do expect that they’ll eventually die out and they’re meant to be “loss with no cross” (meaning, you’re not pissed off about losing it). But a flashlight over $30 should not have a proprietary cell, at least one that can’t be replaced.

Olight had another holiday sale. I bought an iXV i1r2 EOS keychain flashlight. I was expecting USB-C… but this particular holiday red variation came with Micro-USB! I expect they did this to purge their inventory of old Micro-USB ports. Still, very surprising and annoying.

Last but not least, parasitic drain. I have a NiWalker ET mini V2 that is kind of an odd-ball flashlight. It has some interesting design features and is very well made. But I was shocked to find that when idle, the parasitic drain is very high. There’s not even an aux-LED or illuminated button being powered. Anyway, at least the light has physical lockout, which I now do as a usual practice.

All good points.

well, unacceptable depends upon the price….

1. strobe.
2. 5000K or higher.
3. USB-B/A slot.

of course, i will buy one for $6.99
even with all of those. but, $7? nope.

Low CRI, no stabilization, especially on turbo, dedicated cells, tactical switches, strobe, onboard charging and so on.

I can’t really get mad at companies that make proprietary battery lights because in Canada it’s technically not really legal to sell a device with a lithium ion battery that isn’t a proprietary one so like…what’re they supposed to do? But I still wouldn’t buy one. And I don’t want to encourage them. So that’s still one for me too.

Also, not having a magnet on it somewhere. Unless it’s a keychain light or something way too big for a magnet in the tailcap to do anything. And not having stepless ramping.

You mean lack of on board charging?

I think he detests onboard charging. I agree, it can be hit or miss. Some overcharge or don’t provide a stable enough charge. But some do a pretty good job. If you can find one who does it right, it makes for a great reliable and protected charger for other flashlights that use the same cell.

Above a certain price point one should expect an option for Hi CRI if you want it, stable current draw, LVP, thermal limit control… and really, who’d not want a programmable UI like Anduril or NarsilM?

About ramping, I really don’t like stepless. I mean, I can deal with it in something like the RRT-01 that has a magnetic ring for analog control of brightness, but Thrunite has a bad habit of releasing flashlights with stepless ramping and no stepped option.

PWM
Weird UIs with slow smooth ramping, or ones that make you trudge through modes, or have strobe/blinkies as part of the main mode sets. hold for off doesnt bother me too much anymore, as long as it’s properly implemented in the UI.
Poor regulation and thermal management
Green tint
Micro USB if it’s not properly done. The port needs to be protected and designed to prevent improper insertion
Cheap/poor build quality in anything other than a $5 zoomie or pocket light

Generally in the last 2 years lights have gotten better (e.g Wurkkos, Convoy), but there are some from name brands that surprise me with the above

Yea, 1 less thing to broke. Built in charger.