brightness vs colour rendering?

suppose that the led companies watch forums like this one as a way to see what is worth developing...

Should they keep on developing the lumen output of the emmiters, or is it better if they work on getting the light emitted to be as full spectrum as possible? Like either getting white, bluish and yellowish stuff to show up really well like they do now but brighter, or to make the other colours, particularly red and green, more visible?

Well, the current crop of emitters use a blue die with a white phosphor layer on top to produce "mostly" white with a bit of blue. They are trying very hard to produce what's called a RGB (red green blue) led which basically emits an equal amount of all three primary wavelengths to emit a "better" white light. However, this technology is still in development.

Brightness vs color is interesting with the LED's and non-flashaholic users. I have noticed when showing two lights together with the same output non-flashaholics will always state the whiter looking beam is brighter.

I bought 3 P2D-Q5's and gave one to my father and one to my brother and kept one. All three had different tints. When we shine them together they always pick the whiter tint as being the brightest, and I noticed they and many CPF'rs prefer the whitest tints. A more full spectum LED will probably be more yellow in appearance. Many people prefer the light from a LED vs a Incand though it lacks the full spectrum us flashaholics crave. I prefer the warm tones and if comparing will purchase the warmer tint, but I admit the more blue in the light compared to green or yellow, the brighter in appearance it seems. LED tint doesn't matter when shining the light by itself anyway, but it does make a huge difference when shining lights next to each other. My P2D was the warmest of the three. When I brought my Myshondt Nautilas home it looked white until I shined it next to my P2D. Then it looked completely green. When shined by itself though it is my favorite tinted light. I believe it shows colors better and I believe depth perception is better with this light.

Your question raises some interesting thoughts. I wonder myself what the LED manufacturers will do.

Bill
Bill

To me, LEDs that are white seem brighter but they seem to have less depth perception or contrast. White LEDs also seem to cause alot of "glare" for me.

carmatic said:

suppose that the led companies watch forums like this one as a way to see what is worth developing...

Click to expand...

In this thread -

Puny LED flashlights (Not!) + COLOR RENDITION Comparison

I started out just to show that LED brightness has reached a point where it has mostly exceeded incand flashlights even for what were once considered "outrageously" bright - Xenon/Lithium lights like the legendary SureFire 6P (G2, Streamlight Scorpion) and even 9P (3x CR123) -
some LED flashlights even matched a 1,000,000cp spotlight!......(post #27 )

But the discussion also turned to how incands seem to do better outdoors
- so I also compared Color Rendition -

BUT there is also CRI (Color Rendering Index) that is often not understood well - leading to people to quoting incands are close to CRI=100 (perfect) of being better for color rendition -
whereas one can easily see that incands have a very yellow/orange bias, and most people have difficulty differentiating blue, and seeing yellow on white......

So it depends whether one wants true color rendition/accuracy with a high CRI (but remember FWIW incands have CRI=~100!)

Or to have a color balance so one can see well outdoors - and this is DIFFERENT - as -

CRI does NOT necessarily = Accurate Colors
which in turn does NOT necessarily = Seeing Better.......

Read the thread for many comments and ad-hoc experiments to illustrate points made.......

Puny LED flashlights (Not!) + COLOR RENDITION Comparison

Should they keep on developing the lumen output of the emmiters, or is it better if they work on getting the light emitted to be as full spectrum as possible? Like either getting white, bluish and yellowish stuff to show up really well like they do now but brighter, or to make the other colours, particularly red and green, more visible?

Click to expand...

I believe the biggest push for LED companies over the next several years will be to make emitters that are capable of being used in general lighting applications, which will REQUIRE emitters in neutral white (3500k-4500k) and warm white (2700k - 3500k) to come out. Better color rendition will also be a major consideration. Note: color temperature and color rendition are separate issues.

Also, warmer colors actually theoretically have the potential for more lumens -- our eyes are much more sensitive to the yellow/green phosphor emissions from LEDs that the blue light that they are based on -- the only problem now is that adding a thicker layer of phosphor tends to impede light extraction beyond a certain point. As this engineering problem is overcome though, we'll end up seeing lower color-temperature (warmer) white IN ORDER to get more brightness.

BUT there is also CRI (Color Rendering Index) that is often not understood well - leading to people to quoting incands are close to CRI=100 (perfect) of being better for color rendition -
whereas one can easily see that incands have a very yellow/orange bias, and most people have difficulty differentiating blue, and seeing yellow on white......

Click to expand...

CRI is a bit confusing, as it was only really meant to compare lights at the same color temperature. For example, a 3000k halogen at CRI 100 will render color better than a 3000k fluorescent at CRI 80.

Of course, if I were to ask anyone which had better color rendition -- a "long life" incandescent at 2700k, or a severely overdriven halogen at 3500k, just about everyone would say the latter. IMO, a color temperature of 4000K with 100CRI would be ideal for most applications. To get a close approximation of what this looks like, take an Incandescent flashlight, and an LED flashlight with similar beam patterns, and turn on both at the same time -- the incan's yellows/reds complement the cool white LEDs perfectly. The result is more accurate than either one, or the other.

Another thing to keep in mind -- in certain applications, it may be worth sacrificing CRI for contrast -- for example, wearing yellow-tinted glasses during the daytime in order to increase contrast between objects in the foreground against a blue sky. Color rendition with those glasses on is worse, but visiblility might be better for a particular application. Incandescent lighting I find has a similar effect to "blue blocking" sunglasses -- things tend to look deader under incan light than say HID light, but contrast is enhanced.

mmm, good replies

the reason i started the threads was because when i am walking around the woods with my fenix t1 (yay it beat a 1000k candlepower light), the i end up looking at the tree barks and branches, because the foliage and grass dont show up very well...
it seems that the light reflects off the layer of moisture on the leaves, rather than the leaves themselves, because when i try to shine at the evergreen plants they show up as a ghostly pale emerald colour instead of the rich bright green which they look like in daytime...
meanwhile things like the barks of decidious trees show up as an equally ghostly white colour but much much brighter,in daytime they are all different shades of brown, and there is a huge contrast between seeing the barks and the foliage
and on the ground, things like mud are almost pitch black under the torchlight and require the torch's high mode to see properly, while at the same time rocks become glaringly bright... which is not what it looks like under daylight at all, and it makes it tricky and uncomfortable to navigate the woods at night

if you are shining at a house with white walls, for example, then you would feel that the throw of the T1 and other powerful LED lights like it is very good, but soon you realize your not seeing everything with the light

man that colour rendering index sounds helpful, until you read the wikipedia article which says that it doesnt work well with LEDs!

2xTrinity said:

I believe the biggest push for LED companies over the next several years will be to make emitters that are capable of being used in general lighting applications, which will REQUIRE emitters in neutral white (3500k-4500k) and warm white (2700k - 3500k) to come out.

Click to expand...

I agree with this statement and UnknownVT's statement in the previous post about how LED flashlights have exceeded the performance of incan lights. Although LED's are certainly "bright enough" for most flashlight uses, we still have a ways to go until LED's pump out enough lumens to really start competing with other fixed lighting technologies, and until LED's become more common in those applications, I don't think the color rendering issue is that critical to the manufacturers yet. I'm sure they're trying to improve on it, of course, but as long as LED's are still mostly in flashlights and niche applications, I don't believe that the pressure for improving color rendering is that critical yet. They can still tout the efficiency, compactness and durability angle and sell them based on those qualities, even if color rendering is still not optimal.

even today, LEDs have surpassed most lighting technologies in efficiency

HOWEVER, the biggest issue in SSL is lumen/$. it is VERY expensive to make an efficient HIGH LUMEN lighting fixture compared to traditional technology

there is a definite payback period, but until consumers become more willing to spend $80-150 to change their $3 light bulbs, it aitn gonna be big

once the technology hits an efficiency high enough, then the cost per lower lumen output becomes reasonable

warm white LEDs from SOME manufacturers are already in the 80s in CRI whereas others are 70-75 still.

we have been working with a warm white that produces a consistent 3100K, 88 CRI light, at 75 lumens consistently at only 350mA....that is where we have to just begin to make it possible