Cool Lights LED... AMAZING

[jamesbridges]

I own the Zylight Z90, it is terrific! I take it everywhere I go. Being able to program the light-send it to another Zylight isvery cool.
I want to try the larger IS3.

 

[Frank Weeks]

hey jay...any chance of doing a side by side on info tech of these lights and what they are meant to "replace"...like how they compart to say the arri 300 and 650's?

Hey Jay
I know you are not the Nielson rating of lights but this is interesting. The aspect of this test that intrigues me is the value of CRI. The reason I switched from tungsten to Led is because of the CRI. How much difference is there between 90+ CRI and what Cool Lite's is delivering? I respect Stephen Pruitt and Richard snd want to know the real difference between these ratings.

Anyone?

Thanks

 

[Richard Andrewski]

Hey Jay
The reason I switched from tungsten to Led is because of the CRI. How much difference is there between 90+ CRI and what Cool Lite's is delivering? I respect Stephen Pruitt and Richard snd want to know the real difference between these ratings.

Frank,

I'm not sure where you got that Cool Lights LED was CRI 90. On our web page it says CRI 80 under specs. That's where Stephen saw it on our product web page. We've never advertised it as CRI 90. You may have us confused with another similar low priced panel that claims CRI 90.

IMO almost all the LED panels out there using a 5mm daylight mono color LED like ours are also really CRI 80 (or under) as well. In my previous long post on this thread I was talking about the fact that anyone that's claiming CRI 90 for an mono color daylight LED light is most likely misreporting specs as its practically impossible to find a daylight mono color LED of any size with great CRI at this point.

We could just dodge the bullet and report it as CRI 90 like so many others, but even ignoring the moral implications of that, the practical issues are that is easily refuted by anyone that knows something about LEDs, CRI, etc.

As I said, if someone says "its a bit toward the greenish side" and "its CRI 90", those two statements don't add up and one or the other is false.

One interesting thing, if you look at the super expensive models that someone posted a few posts back and look at their specs, they don't even mention CRI in some cases. Just vague mentions about it. Wonder what that means?

All that being said, this is proof that CRI isn't everything. We have a ton of happy users out there using this panel in every day common video/film settings and not complaining about the color rendering. If they find an issue, they simply fix it with 1/8 to 1/4 minusgreen gel. But then, I set expectations appropriately too beforehand so most have known that LEDs may need this kind of correction in some cases.

 

[Policar]

CRI is a meaningless term; it stands for "Color Rendering Index" and is intended to quantify the percentage of a perfect bell curve spectrum represented by a light source. I believe it nominally signifies the percentage of wavelengths produced as compared with black body radiation, but that's a stupid way of measuring light quality.

Basically, if a tungsten filament heated to 3200ºK delivers a bell curve around 3200ºK but extending pretty far into both warmer and cooler light, a fluorescent bulb with a CRI of 90 should reproduce 90% of the wavelengths on this curve. So that's simple: the more CRI, the better the light.

But it's not simple. Most spectra from HMIs, discharge lamps, fluorescent bulbs, and LEDs look NOTHING like a curve. Sodium street lamps produce two visually indifferentiable wavelengths; is that a CRI of 0? Cool white fluorescent bulbs represent a broad spectrum but they have a huge spike at green. (Whereas a bell curve at green looks pure white.) How do you measure that in terms of CRI? You can't. LEDs, meanwhile, should emit a single wavelength, but they can be coated with phosphors (like fluorescent bulbs are) to emit more. But uhh...how many more wavelengths and which ones?

The only way to know is to compare. (Unless you use carbon arcs, tungsten lights, and the sun exclusively. HMIs and kino-flos are nice too, but not perfect.) Two nominally 5600K sources could produce different looking light, even if the majority of it lies in the same area of the spectrum. One test is to put a CD-R near the lamp and see how smooth the spectrum that reflects is and which colors are most represented. The best test is to shoot footage.

 

[Richard Andrewski]

-How do you measure that in terms of CRI? You can't. LEDs, meanwhile, should emit a single wavelength, but they can be coated with phosphors (like fluorescent bulbs are) to emit more. But uhh...how many more wavelengths and which ones?

That's my point. They don't know how to make the simulated full spectrum well yet with a single mono color 5600K LED. Best chance to get full spectrum daylight simulation is to use at the very least two colors of LEDs (ideally about 3000K and 8000K) in the same panel and mix them or RGB LEDs and custom mix into levels of white and as a side benefit you also can get single wavelength colors as well. No need for a red, green or blue gel anymore with a panel like that.

On a practical level, and dealing with many of the modern light sources beyond daylight, tungsten and carbon arc (all the true full spectrum sources), CRI becomes a practical measure of how far off they are from being balanced on the green / magenta axis.

Toward the middle, you should be okay for color rendering (also considering that the color temperature of the light is something your digital medium's white balance or film, if you prefer, can deal with).

Skewed too far toward green or magenta and you get lower CRI also. Most of the time though, in the kinds of lighting we deal with these days, its mostly toward the green end to one extent or another. And also since most people are using digital mediums today with fantastic white balance capability, the green magenta axis is well compensated for in many cases and any shortcomings of that light will be minimized.

 

[Frank Weeks]

QUOTE]I'm not sure where you got that Cool Lights LED was CRI 90[/QUOTE]

That's not what I meant. I know Cool Lights are around CRI 80. I was just wondering about the real world difference between 80+ and others that claim 90 but cost 3 or 4 times as much.

For the record I have 4 cool lights and think there great.

The only way to know is to compare.

agreed

 

[Jay A. Kelley]

Hey Jay
I know you are not the Nielson rating of lights but this is interesting. The aspect of this test that intrigues me is the value of CRI. The reason I switched from tungsten to Led is because of the CRI. How much difference is there between 90+ CRI and what Cool Lite's is delivering? I respect Stephen Pruitt and Richard snd want to know the real difference between these ratings.

Anyone?

Thanks

You guys are reading my mind. I had planned to do a test of different fixtures and their qualities on the show.

But it's a tough thing to put into practice. Goal needs to be looking at them like different recipies, not which one is better/worse..

But yeah, I would be willing to do a show like that.

I need some newer Kino style, and a couple HMI fixtures to do it with.

Jay

 

[Richard Andrewski]

Should be an interesting test and I welcome it. We can provide some of the flos and HMI type fixtures as well.

 

[Stephen Pruitt]

In my opinion it is pretty difficult to understate the importance of CRI in measuring light quality. I have a closet in our house where the bulb must have a CRI of maybe 50. (It's either too much hassle to change, or I'm too lazy, or, more likely, both.) I can't tell the difference between green, blue, and black in that room. There's just no green or blue in the light, so they all look exactly the same. I actually have to pull things out into the daylight of the bathroom to see what color I'm about to wear. And trust me, that bathroom check has saved my rump more than once. ("I can't believe I was going to wear that combination!") That's an example of a CRI problem on a big scale.

In answer to Videodisc's question, though, I'm doubting if too many people would notice that much difference between a CRI of 80 and a CRI of 90 in most everyday situations. And these differences could probably be color-corrected away. Basically, some colors on a chip chart at 80 will be too intense and others will be too subtle, but it wouldn't be like night and day different. Same story for HMIs versus sunlight.

Like I said, having tried LEDs, I just couldn't deal with the multiple shadows much more than my problems with the CRI. But others will and obviously do feel differently, as this thread clearly demonstrates. After all, everything we do in artificial lighting (and most of what we do using natural light) is a compromise of some sort vis-a-vis the "perfect" sunlit day (whatever that looks like to you). The one thing I do know, though, is that my perfect sunlit day doesn't cast 100 different shadows.



Stephen

 

[Alexander Nikishin]

Just got my LED600 unit today....

Right off the bat I can say that the build on the unit is great.

Well designed sturdy housing, barn door tray and barns are smooth & easy to set, stiff v-lock battery plate, nice top handle and there's even a pocket filled carry bag included to transpo the unit.

I just slid on a fully charged RED brick, turned on all 5 banks and dimmed them up to full power to see how long the unit will run on full blast for....will report back.

I have multiple Arri 650 fresnel heads and a Kino 4x4 with daylight tubes....if I have the time in between productions I will set all three up and see what the difference in the quality of light is like.

Overall I am quite surprised so far with what this little light can do in such a compact body and even more so with such a compact price! =)

 

[Richard Andrewski]

Thanks Alex for your comments. I think you'll get about 2:45 with the Red V 140WH Brick. Also my comparisons in lux output to an Arri 650w are based on photometric readings I got off their site. I would love to hear a real world comparison in terms of lux output of the flood unit you got and one of your 650s in both flood, medium and spot configs. Our spot panel (out of stock now) is about 1200 lux more than the flood one.


Stephen, what kind of light do you have in your bathroom? That's wild.

 

[Gary Stone]

awesome. i'm excited to see a test!!!

 

[Richard Andrewski]

Here are some color test charts I shot with my RED some months ago (build 15). The conditions were to use camera WB 5600K preset so you could see how far off the particular source was in that kind of condition in both color temperature and CRI. If I had used custom white balance, they'd all look about the same so that wasn't a valid test for what I wanted to accomplish. I should add that they were all taken in 4K and cropped/reduced in RED Cine. Then reduced again in PS so they wouldn't be huge here.

The first one was taken outside at noon and I was trying for a cloudy day which would be closer to 5600Kish, but it just didn't happen that week so I took one anyway. The real color temperature outside was about 4700K so you can visibly see that difference given the preset 5600K setting in the camera:

This is a Cool Lights LED 600 5600K flood:

Cool Lights CL-655 Studio model with 6 CL-5556 5600K 55w tubes:

Cool Lights CDM 150 Fresnel with 5400K CDM (para HMI) bulb:

 

[Richard Andrewski]

And for fun, this one was taken before I got my RED with a still camera so not exactly the same conditions. It was a test of a 35w HID bulb when I was looking for Xenon bulbs to create a CDM 35 fresnel (arri 150w tungsten pepper size). The problem with these bulbs is, try as hard as they can, they can't get above about CRI 60 at this time. This kind of thing will most often manifest itself as too much green all these kinds of bulbs from fluorescent to CDM to LEDs:

 

[Jay A. Kelley]

Richard, put a minus green on the light and take one more pic.. I'm curious to see the results.

Jay

 

[Richard Andrewski]

If you mean on the last one--the 35w HID, I'll try to dig it out and hook it all back up again. Probably buried deep in the closet if I still have it. Thats from summer of 2007 so a lots happened since then. Even a custom white balance would take care of most if not all that green spike IMO.

A super low wattage xenon 35w would be a great little efficient fixture but it would definitely require a minus green filter built in until we can get a better bulb.

 

[Stephen Pruitt]

As expected, the differences are clearly evident, but relatively subtle. For some reason that upper set of color blocks is all over the place from shot to shot. It would have been nice to see actual daylight at 5600K.

I'd like to see a replication with the auto-white balance engaged. That's where we'll notice the real differences. If, in making a true white with the available light, the camera really messes up the colors, that's your CRI at work right there.

That 60ish CRI is a mess.

I will say that the build quality on Richard's LED units is terrific. The pleasures and terrors of China.

Stephen

 

[Richard Andrewski]

Thats probably because I wasn't careful with the angle of the test chart each time so maybe a bit more of a slant in leaning against something. A better test would be to put the chart in one place, perfectly at a 90 degree angle, perform all the tests the same day (these were different days) and be a bit more careful on exposure too. The last CDM picture on the first group is a bit more hot I see that now.

Another issue I'm not sure about when making tests like these is glare of some of the harder lights against the test chart like the CDM. Putting the light behind diffusion or bouncing off something risks contaminating the test so I didn't do that. What to do about the glare which may skew the results somewhat?

 

[Richard Andrewski]

I do have the with and without white balance on a couple of those. Wish I would have done it on all of them. This is the same LED 600 flood test again for comparison purposes with the 5600K preset:

This is the flood after custom white balance:

 

[Richard Andrewski]

This is the 655 before and after: