fire-stick
Enlightened
Bascally is what I'm wanting to know is how much of a drop in output will it take to be visible noticeable?
Thanks
Scott
Thanks
Scott
Would it be visibly noticeable if a flashlight went from a 100% output to 90% ?
- Thread starter fire-stick
- Start date
Help Support Candle Power Flashlight Forum
No.
Your eyes have a roughly logarithmic response to light, so you would not detect a 10% reduction in actual light as a 10% reduction in stimulation. The reduction in sensation would be maybe 2%. It's probably not detectable, even with 2 lights side by side.
Scott
PS: Just reread your post.
There is an optometrist or two floating around here, that's really who you need to answer this.
Just for the sake of argument, lets say that 1) your eyes have a precisely logarithmic response, and 2) you need a 10% change in senation to tell a difference. Mathematically let's say that means log(a)/log(b) = 0.9 for two brightnesses 'a' and 'b'. That means 'a' (the dimmer of the two) is around 63% as bright as b. Basically you would need to increase or decrease the actual brightness by 1/3 before you could readily tell.
Those aren't real numbers, but it shows you how the thing works. I don't think I am horribly far off.
Your eyes have a roughly logarithmic response to light, so you would not detect a 10% reduction in actual light as a 10% reduction in stimulation. The reduction in sensation would be maybe 2%. It's probably not detectable, even with 2 lights side by side.
Scott
PS: Just reread your post.
There is an optometrist or two floating around here, that's really who you need to answer this.
Just for the sake of argument, lets say that 1) your eyes have a precisely logarithmic response, and 2) you need a 10% change in senation to tell a difference. Mathematically let's say that means log(a)/log(b) = 0.9 for two brightnesses 'a' and 'b'. That means 'a' (the dimmer of the two) is around 63% as bright as b. Basically you would need to increase or decrease the actual brightness by 1/3 before you could readily tell.
Those aren't real numbers, but it shows you how the thing works. I don't think I am horribly far off.
Last edited:
IsaacHayes
Flashlight Enthusiast
Depends probably too on how bright the light is to begin with.
I can tell differences pretty good. But only when changing back/forth between 90-100% could you really tell. If you used one, then put it down, picked up again 10mins later with 90% output, you'd have a hard time telling.
I can tell differences pretty good. But only when changing back/forth between 90-100% could you really tell. If you used one, then put it down, picked up again 10mins later with 90% output, you'd have a hard time telling.
VidPro
Flashlight Enthusiast
IsaacHayes said:
yup what he said. from 1W to 3W on my 2 mode lights, i have to either side by side, or switch it while specifically looking at the light it puts out to tell.
3x as much light, and IF you put it down for 10 minutes you would have a hard time telling.
On the other hand, when i am trying to look at something far away in the dark, at the creek or in the woods, that extra 2W is all the difference in the world.
90% though? even if it was off for 2 seconds, i could probably not tell that small of a difference.
my experience is power based, not lumen or lux specific, efficiency is higher at lower powers with leds, but the basic idea is still the same.
if my light dropped to even 80% slowly while using it in a single session, i would probably not notice , because within that session, my eyes would be adjusting to the situation. sooooo if my light went down slowly, it would not bother me much.
i can alwasy squint and try harder with the retina, and brain, but if you dont have to thats cool too
arent incadescent lights running with alkies, dropping MUCH worse than that all the time, and untill its very low, most people dont have a big issue with it.
Last edited:
JohnK
Flashlight Enthusiast
Well, I'm the optometrist, but I can only tell you what I have learned here.
I did NOT believe the statement that you need about a 50% increase/decrease in brightness (lumens) to notice the difference. Totally rejected it. Enda !
Then I purchased a LOT of lights.
As stated above, unless you have the two lights on at the same time, and side by side, it is VERY difficult to tell rather large differences in brightness. That's the way it is.
I own a Fenix LIP, and a Streamlight 4AA Luxeon. Quickbeams tests show the Fenix has about 70% of the brightness of the SL. They have very similar beams, corona, and spill.
If I go outside in the DARK, no ambient light, and do not have the lights together, it is difficult to tell the difference. Side by side, yes.
Interesting subject, to say the least.
I did NOT believe the statement that you need about a 50% increase/decrease in brightness (lumens) to notice the difference. Totally rejected it. Enda !
Then I purchased a LOT of lights.
As stated above, unless you have the two lights on at the same time, and side by side, it is VERY difficult to tell rather large differences in brightness. That's the way it is.
I own a Fenix LIP, and a Streamlight 4AA Luxeon. Quickbeams tests show the Fenix has about 70% of the brightness of the SL. They have very similar beams, corona, and spill.
If I go outside in the DARK, no ambient light, and do not have the lights together, it is difficult to tell the difference. Side by side, yes.
Interesting subject, to say the least.
Roy
Farewell our Curmudgeon Administrator
When I joined the CPF back in the spring of '02, the rule of thumb was sthat it took about a 50% change in the light level before MOST people would notice the change. That became the basis for defining runtime as the time it takes a light to change by 50% of MAX brightness.
Yooper
Enlightened
I'm not an optometrist (OD). I'm an ophthalmologist (MD). Because of the logarithmic response curve, with an average healthy visual system most people require about a 50% difference in brightness to distinguish a difference. You can train yourself to do better, but a 10% difference would be really tough to see, even with side by side comparison.
