Perceptions of "brightness"???

Maybe it's just me, but I'm having trouble differentiating between the levels of brightness on my three lights -- my C3, U2 on high, and McLux III PD on high all look about the same to me in terms of brightness. What gives? The C3 and U2 may be close, but the PD shouldn't be.

Couple of possibilities:
1. My eyes can't tell the difference very easily
2. I got a bum C3 and U2 and a great PD?
3. The C3 and U2 are great, and the PD is fantastic?
4. I'm clinically insane?

Background info (if it helps) -- My U2 I can tell has the slightest blue tint to it when compared to the PD. The PD has no tint at all from what I can tell. The C3 does have fresh batteries.

I think 1 & 2 are both correct.

I'm reserving number 4 for myself.

Unless their brightness differs at least 20% (IIRC), your eyes won't perceive the difference.

Slightly OT: my perception of brightness has indeed changed since I joined CPF. I used to think my 4D Mag was *bright*, until I got my Peli M6. :wow: Same thing with my GL3R; I compared it the other day against my old 4D Mag, and there's simply no comparison -the GL3 wins. I'm blown away by so much light coming from such a small light (comparatively speaking). I've been happy with my GL3. However, recently I started feeling like even that's not bright enough. Same thing with my new NG500 sammie (in minimag); they're not bright enough (at least to my eyes).

... and then the other night, I was playing with attaching my NG500 to my bike helmet, I set it down on the table, walked across the room and tried to look directly at it... :wow: that thing is really bright!! Still gotta do the same with my GL3...

As already stated, your eyes are poor judges of "brightness", and ESPECIALLY poor judges of overall output.

One of the 1st things you notice when using a lux meter is that large variations in measured output are barely visible. Even IF both beam patterns were identical, +/- 20% output is barely visible to the eye. Differing beam patterns and tint makes it almost impossible to accurately judge brightness visually just looking at the beam pattern.

When eyeballing relative output of two flashlights, if you alternately bounce each beam off the ceiling while looking at room objects, you can often better judge which has more output.

Without this, your eyes are easily fooled. The U2 is a good example. My U2 has tremendous output, but doesn't look super bright to the eye. That's because your eye prioritizes the hotspot, and the U2 diverts much of its output to the spillbeam.

I think the PD has a tighter hotspot and dimmer spillbeam, which at first glance looks "bright", making it seem equal to the more powerful U2.

But if you measured ceiling reflection with a lux meter, I'll bet the U2 is much more powerful.

Your C3 should have more output than your U2. However my TL-3 (about equal to C3 in overall output) should also be brighter than my U2. Yet when I do ceiling reflection lux meter tests, they are about equal. Either my U2 is extra strong, or the TL-3 is weak. Yet the TL-3 throws much better since the beam design puts more power in the hotspot and less in the spillbeam.

So in my case a significant difference between measured overall output (U2 and TL-3 equal) vs VISUAL assessment (TL-3 throws better and looks "brighter").

You can get a cheap lux meter for $39. It might be informative to get one and measure ceiling/wall reflection of your flashlights.

I hope for you it's #3 (one bum Surefire, OK, but two?).

#4 applies to pretty much everyone around here...

And, sorry to say this, your PD HAS a tint. It's the tint you personally 'define' as white.

Every LED, heck, even every INCAN, has a tint. You just need some luck to find two LEDs with indistinguishable tint, whereas most incans have more or less the same.

Whenever I compared my 'best' LED against my newest acquired light (which I had used for an hour exclusively, from taking it out of the package), invariably the 'old' one looked blue, green, yellow, purple to the white 'new' one. Later, after I handled the 'old' one for a while, the 'old' looked white compared to the green, yellow, purple, etc. 'new' one...

Once I realized that it's just my perception, and neither me nor most manufacturer have any measurement capability for this (you need to measure the spectrum -- intensity vs. wavelength), I started to ignore tints. In fact, I slightly prefer greenish ones -- they're the brightest to human eyes, and skin discolorations are easier to recognize (if you have some skin problems, and inspect it regularly, that is).

(Privately, I think that "guaranteed tint" is a fad -- you get what this one person prefers, not what you think is white.)

Thanks for the info guys. After a LOT of comparison I can see that the PD has "less" output, but it is definitely not a considerable difference. Since it should be less than half the output of the others I expected a dramatic difference. Very cool though, I'm quite happy.

And I still don't see any tint in my PD. You're probably right about the tint thing, but when compared to my other LEDs, this one still comes up as pure white. So whatever it is, my eye has decided that this is white.

It's interesting that we put so much emphasis on getting a few more lumens, but the truth of it is that maybe we won't even be able to notice. :laughing:

Oh, and 4 definitely applies at this point

WilsonCQB1911 said: "...Since it should be less than half the output of the others I expected a dramatic difference...."

That is a common misconception. Actually the VISIBLE difference is much less for two lights, one with 1/2 the output.

According to Stevens' Power Law the visible difference is the difference of the cube roots: http://en.wikipedia.org/wiki/Stevens'_Power_Law

Consider two lights with IDENTICAL beam patterns, one 100 lumens and the other 50 lumens:

100^.33 - 50^.33 =
4.57 - 3.64 =
0.93, or:
The 50 lumen light will be 3.64/4.57 or 80% of the visible brightness of the 100 lumen light.

Expressed as dB, the formula is:

db = 10 log (p2/p1), so
10 log (100/50) = 3 dB difference

The visible difference is further obscured if the beam patterns differ. The U2 diverts much of its output to spillbeam, but the PD allocates more power to its hotspot. Your eye tends to disregard the spillbeam and focus on the hotspot. Therefore the PD may appear brighter and the U2 less bright than their overall outputs would imply.

Yeah, for such simple things, flashlights can be complicated and irritating.

In my experience, beam pattern is everything as far as perceived brightness. For example, I was recently comparing three fairly similar lights an Inova T3, Streamlight TL2 LED (2nd Gen) and a Maxfire with a TW0K-modified BUG Lux III Module on 2 R123s. The are all Lux lights with some form of regulation that run on 2 123 cells, are very similar looking at Quickbeam's reviews and I paid *roughly* the same price for each. Just shining them around the dark living room/dining room, they didn't seem radically different from one another and even the tints were very similar. Granted, the T3 has a large but relatively dim (compared to the others) hotspot and no sidespill and the hotspot of the TL-2 was smaller than that of the B)G, but taken outside, to my eyes, the T3 seemed to have the least throw and the BOG module the most (keep in mind, it is modded and running on R123s) but if I shine them each into my eyes for just a fraction of a second (to mimic the 'stunning effect' an opponent might experience) the T3 absolutely seemed the brightest.

Beam patterns, baby!

I've also been building a lot more modded Minimags just with cheap CS LEDs, 35k LEDs, THC3, LEDs, MJLEDs etc and have been comparing them against each other... In my experience, once you figure out which one you like for whatever reason, I start seeing all the 'flaws' in the other ones, which I guess is human nature. But if you hand any of those to a reasonable person, they are quite impressed with the output.

Of course, I guess that's why most of us are here... we are NOT reasonable people.

Joema, cool -- thank you very much for the info. Some of you guys really know your stuff. That's very interesting about how output is perceived.

"Of course, I guess that's why most of us are here... we are NOT reasonable people" <--- TRUE for sure. I know it applies to me.