A couple of newbie questions

[Farhad Gulemov]

Hi,

I have recently purchased my first LED flashlight. After doing some research on the Internet I settled for the Fenix TK40 and I have to say that I absolutely love this flashlight. However, I also have some very basic questions about it:

a) The TK40 features a "high" mode which throws 277 lumens and a "turbo" mode which throws 630 lumens. I had somehow imagined that 630 lumens would be roughly 3 times as much light as 277 lumens, but that is not the case. Yes, the "turbo" mode results in very perceptibly more light, but not 3 times more. I am wondering whether to double the light output you need to decuplate (10x) the lumens of the LED. If that is the case, there would be some kind of limit after which it would make little sense to add power to a flashlight. I am correct?

b) flashlights are often rated on the Internet in terms of Watts. I did not see a Watt consumption rating for the TK-40. Why is that? Does anybody know how many watts the TK-40 consumes?

c) units: what is the best measure of who much light a flashliht atually throws? Lumens? Lux'? Watts?

Thanks in advance for any explanations!

Kind regards,

Farhad

 

[headophile]

as far as i know:

a.) 630 lumens is closer to 277 x2 than x3 (2.27 to be exact). i'm pretty sure that if you took 2 tk40s, put them both on high (277 lumen mode) and overlap the beams, it would look just a little less bright than 1 tk40 on turbo.

b.) different lighting methods have different efficiencies (in lumens per watt), hid being the most efficient, then led, then incan. rating flashlights in watts would almost amount to nothing if you didn't know what lighting technology it uses. maybe the experts can give the actual efficiency figures here.

btw, watts = volts x amps.

c.) a higher lumen light with a reflector designed for flood can easily be out thrown by a lower lumen light with a reflector optimized for throw. i believe lux is a measurement of the amount of light hitting a surface whereas lumen refers to the perceived amount of light coming from the source of light itself. hence, lux is the appropriate measurement for throw.

cpf experts, feel free correct me if i'm wrong in any of these things

 

[strinq]

as for:

a. it takes 4 times as much output for the human eye to perceive something to be twice as bright.

b. want to know myself

c. lux = used to measure throw (2nd poster got it right). Lumens = brightness

 

[headophile]

higher efficiency means more lumens per watt. say, you have an hid bulb, a led emitter and an incan bulb which are all rated at 10 watts. the hid bulb will be the brightest, then the led, then the incan. lumens make more sense as a standard measurement for flashlights because it doesn't take power consumption into account, only the brightness. you'd have an idea of how much light the product makes regardless of the lightning technology it uses.

i think the specs on the tk40 are around 6v and 2.8a. using the formula:

~6v x ~2.8a = ~16 watts

hope this helps.

 

[CaseyS]

This article says the current draw for a TK40 is as follows:

Lo: 25ma
Medium: 250 ma
Hi: 700 to 800ma
Turbo 2.6 amps

http://www.candlepowerforums.com/vb/showthread.php?t=229296

As headophile mentioned, you can multiply the volts x amps to get the watts.

 

[Farhad Gulemov]

Thank you all for your very interesting replies and for clarifying things for me. I really appreciate it!

 

[chaosmagnet]

:welcome:

 

[Marduke]

Headophile, you may want to double check your figures

2.8A x ~3.6v = ~10W

You can't mix the drive current and battery supply voltage

Also, LED's are more efficient than HID's, though they are in different power classes (for now).

But in general, it is best to ignore wattage ratings in lights, as it tells you absolutely nothing. Lumen ratings are also often suspect, but is a better rating of brightness if they can be believed.

 

[headophile]

Headophile, you may want to double check your figures

2.8A x ~3.6v = ~10W

You can't mix the drive current and battery supply voltage

Also, LED's are more efficient than HID's, though they are in different power classes (for now).

But in general, it is best to ignore wattage ratings in lights, as it tells you absolutely nothing. Lumen ratings are also often suspect, but is a better rating of brightness if they can be believed.

thanks for the corrections marduke. just a quick question:

don't hid's give more brightness per watt? in what way are leds more efficient?

 

[Marduke]

thanks for the corrections marduke. just a quick question:

don't hid's give more brightness per watt? in what way are leds more efficient?

Modern LED's have a higher luminous efficacy than HID's. ie, they give more lumens per watt.

 

[Egsise]

a) The TK40 features a "high" mode which throws 277 lumens and a "turbo" mode which throws 630 lumens. I had somehow imagined that 630 lumens would be roughly 3 times as much light as 277 lumens, but that is not the case. Yes, the "turbo" mode results in very perceptibly more light, but not 3 times more. I am wondering whether to double the light output you need to decuplate (10x) the lumens of the LED. If that is the case, there would be some kind of limit after which it would make little sense to add power to a flashlight. I am correct?

What batteries are you using?

 

[headophile]

Modern LED's have a higher luminous efficacy than HID's. ie, they give more lumens per watt.

i must've been reading outdated literature then. thanks

 

[Saint_Dogbert]

The human eye has a logarithmic response, specifically a light must be at least 4x as bright as another to give the impression of 2x the brightness.

 

[Farhad Gulemov]

Modern LED's have a higher luminous efficacy than HID's. ie, they give more lumens per watt.

I have never heard of HIDs before. What kind of flashlights use them and how to they compare to LED flashlights?

 

[Marduke]

I have never heard of HIDs before. What kind of flashlights use them and how to they compare to LED flashlights?

I suggest reading through the Welcome Mat, and reading through the Wikipedia article on them for a primer.