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Author Topic: Do SoLux bulbs meet color temp specs?  (Read 8558 times)
Frans Waterlander
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« on: June 20, 2013, 01:36:40 PM »
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Some people say that SoLux bulbs fail to meet their CCT spec by up to 1000K and some say they meet specs. If you have test results one way or the other, I'd like to hear from you, because I'd like to set the record straight. I have no connection to SoLux, other than using their bulbs in my digital darkroom and being satisfied with their performance.

My own measurements and information supplied by SoLux and the Intertek test lab indicate that SoLux bulbs meet their color temp spec within +/- 200K. SoLux maintains that in all cases where they got an opportunity to review the test set up when out of spec results were reported, they showed incorrect test setups related to light contamination from the backs of the bulbs or otherwise and/or incorrectly powering the bulbs. After corrections were made the bulbs tested within spec.

If you tested out of spec, did you work with Phillip Bradfield or Kevin McGuire at SoLux to resolve the issue and what was the result?
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digitaldog
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« Reply #1 on: June 20, 2013, 04:25:07 PM »
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The above as I mentioned at PhotoNet is to be expected (the numbers don't mean much, they are correlated). This CCT4700K lamp, inserted within a Solux lamp housing by their design fails as it's off by CCT 451K. So what?
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Andrew Rodney
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« Reply #2 on: June 20, 2013, 05:20:28 PM »
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Solux's website is a bit puzzling. Apparently their PAR lamp "reproduces the full color spectrum of natural daylight at 3500K!" (my emphasis).

Honest, see here: https://www.solux.net/cgi-bin/tlistore/soluxparbulbs.html

At least 2000K off, right from the git-go  Wink

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Frans Waterlander
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« Reply #3 on: June 20, 2013, 05:38:44 PM »
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So what? If you measure a product to not meet specs and you publish those results, decency dictates to work with the seller. And doing that before publishing your results would be even better.
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digitaldog
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« Reply #4 on: June 20, 2013, 05:58:47 PM »
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So what? If you measure a product to not meet specs and you publish those results, decency dictates to work with the seller.

No it doesn't. I'm not buying their values because they are CCT. Just as I don't buy a spec that says the light is D50: there's only one device that can produce that and it's really far away plus D50 is a number of measurements made across the planet to boot.
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Andrew Rodney
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« Reply #5 on: June 20, 2013, 07:00:35 PM »
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Apparently their PAR lamp "reproduces the full color spectrum of natural daylight at 3500K!"

That means that the PAR lamp puts out a full spectrum (spectral power distribution or SPD) of daylight with a color temp of 3500ºK. Yes, that's 2000ºK less than 5500ºK, but the spec says 3500ºK. They also have 12v lamps that range from 3500ºK to 4100ºK, 4700ºK and 5000ºK.

Back to the OP a couple of hundred degrees difference is negligible when used as a viewing light because your eyes will compensate (white adaptation). A couple hundred degrees would be more relevant when talking about a light designed to shooting film or digital. But it's really the evenness of the SPD that matters there...plus, it's not hard to white balance a few hundred K.
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Jack Varney
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« Reply #6 on: June 20, 2013, 09:06:26 PM »
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When you tire of specs just try them and compare them to other lamps. They work for me.
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Jack Varney
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« Reply #7 on: June 20, 2013, 09:09:14 PM »
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When you tire of specs just try them and compare them to other lamps. They work for me.

Exactly! They have a lovely spectrum and light quality. The numbers are pretty meaningless (hence the 5000K units which are 4700K, driven hotter to burn out faster and cost you more).
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Andrew Rodney
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« Reply #8 on: June 20, 2013, 09:45:32 PM »
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The numbers are pretty meaningless (hence the 5000K units which are 4700K, driven hotter to burn out faster and cost you more).

Well, the numbers have meaning but they are relative...I have a GTI light box which I've re-lamped with D65 bulbs which are kinda cool (but match my displays) and I've got a Solux task lamp with 4700ºK bulbs which are a bit warm. Using the two I can evaluate near daylight and near tungsten and compare the prints under both. The advantage of the Solux is that they have a better, less spiky SPD. I also have a 3500ºK bulb I can pop in if I need a eval closer to tungsten (I rarely use it).
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Frans Waterlander
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« Reply #9 on: June 20, 2013, 10:05:01 PM »
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OK Andrew,

Let me get this straight: SoLux says the 4700K bulb should have a CCT of 4700K +/- 200K. You measure a CCT of 4249K, declare that they fail to meet their published specifications, publish your results without talking to SoLux and apparently are not planning to do so, and you say so what? This, to me, is unbelievable. This, what looks like a devil-may-care attitude, would never fly in my career in the electronics industry in R&D, marketing and quality engineering.
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Tim Lookingbill
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« Reply #10 on: June 21, 2013, 01:22:13 AM »
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OK Andrew,

Let me get this straight: SoLux says the 4700K bulb should have a CCT of 4700K +/- 200K. You measure a CCT of 4249K, declare that they fail to meet their published specifications, publish your results without talking to SoLux and apparently are not planning to do so, and you say so what? This, to me, is unbelievable. This, what looks like a devil-may-care attitude, would never fly in my career in the electronics industry in R&D, marketing and quality engineering.

You have a career in electronics?! OH JOY!

Could you R&D and design decent MR16 circuitry into a task lamp whose 110v>12v power converter won't crap out after 40 hours of use? I mean could ya'?! REALLY?! Could ya?! That would really help a small group of photographers out who bought a Solux bulb but can't find reliable lamps to drive it.
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digitaldog
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« Reply #11 on: June 21, 2013, 08:13:18 AM »
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Let me get this straight: SoLux says the 4700K bulb should have a CCT of 4700K +/- 200K. You measure a CCT of 4249K, declare that they fail to meet their published specifications, publish your results without talking to SoLux and apparently are not planning to do so, and you say so what?

I do. Not just I as you know.

At least two other's from the ColorSync list, one a respected color scientist (Robin Myers who wrote SpectraShop) with a $13,000 spectroradiometer and i1Pro who's data correlated well with mine and others. LuLa audience: This is all known to Franz and I'll copy and paste the same data from the CS list that Franz saw below. When presented this data, Franz said they (and presumably now I) did the measurements wrong. Besides what the marketing department at Solux has placed in their spec sheet, the only other person to get a value that's within what Solux provides is Franz, using a 10 year old Minolta Color meter!

To answer your question Franz, I think you are confusing marketing spec's with science here. It is not up to us to disprove Solux's numbers although we have done so to a degree (at least three independent end users reported the numbers don't jive with the spec's). It's up to Solux to provide an exact process used and for us to then correlate or not. They have not done this! They have the ability to post here, PhotoNet where you started all this, and more appropriately on the ColorSync list. They didn't in 2009 after Robin and other's posted their findings! Why don't you find out what instrument they used, the software used, and the exact testing process used to get their numbers? 

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This, what looks like a devil-may-care attitude, would never fly in my career in the electronics industry in R&D, marketing and quality engineering.

It is you sir that has the devil may care attitude. You don't have the equipment appropriately to measure the SPD and produce the CCT values. You haven't provided any testing methodology Solux used to get their values but you've now posted about this in three forums and when others using at least the correct instrumentation provide values that don't jive with Solux, you have the nerve to tell us we are doing the measurements wrong! You blindly accept the marketing driven spec sheet of a company who's products everyone so far agree's is a good product and who all dismiss the values. It's a shocking attitude from someone who says he's got a bkgnd in the electronics industry. Worse, far worse is this is all due to your article, hosted on the Solux site that states we should all be using Solux 5000K bulbs and calibrate our displays to 5000K, after which we'll get a match. Anyone else here on LuLa find that approach doesn't work?

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Subject: Re: Solux Bulb color temperature
From: Robin Myers
Date: Tue, 17 Feb 2009
Here are the CCT results from measuring a Solux 4700K bulb, and two Solux 5000K bulbs (one with clear sides, one with black sides). The measurements were made 1 m from the front of the fixture to the measuring devices aperture.

i1 Pro with Ambient filter

Solux 4700 50W 36-degree 4304K +-4K
Solux 5000 35 W 36-degree Clear 3974K +- 3K
Solux 5000 35 W 36-degree Black 4428K +-7K
PR-655 with CR-655 Cosine Corrector

Solux 4700 50W 36-degree 4431K +-2K
Solux 5000 35 W 36-degree Clear 4025K +- 4K
Solux 5000 35 W 36-degree Black 4528K +-2K

With only one sample each of the 5000K bulbs, it was not possible to double-check the 5000K Clear bulb, but it is apparent that the 5000K bulb is not right. I suspect it is a mismarked lower Kelvin bulb or a bad bulb.
Otherwise, the i1 Pro and the PR-655 agree. There were two different setups, at two different locations but the light fixture was the same and the bulbs were the same for both sets of tests. The CCT was calculated with SpectraShop 3 (to be released later this week, hopefully) and the CCT results of 5 to 6 measurements of each bulb were averaged.
The calculated CCTs do not agree with the expectation based on the manufacturer's marketing.
In comparing the emission spectrums, the i1 Pro and PR-655 agree fairly well. Both of them have a general shape similar to the D50 curve, but much smoother. There are several small peaks in the D50 spectrum absent from the measured Solux spectra. The manufacturer has claimed a spectral shape similar to D50 and it is a reasonable approximation.
In Ken Fleisher's original post, he reported a CCT of 4450K for the Solux 4700K bulbs and the results above agree with the lower than claimed CCT value (if you believe the "4700 Kelvin" on the bulb's box means CCT).

Robin Myers

And

Quote
Subject: RE: Solux Bulb color temperature
From: "Tim Vitale" <email@hidden>
Date: Tue, 17 Feb 2009 11:21:24 -0800
I have four Solux 4700 K 36deg floods that are about 1-2 years old
with 100-300 hours (or so) on them. The only variation can be hours
of use. I will be ordering a new batch quite soon. If you are still
interested get back to me in 7-10 days and I'll report the newest
findings.
# 1 = 4363 K
# 2 = 4550 K
# 3 = 4307 K
# 4 = 4456 K
They were measured with an i1 Rev D (UV incl) in Emissive-Light mode,
using Robin Myers SpectraShop.
As Robin said earlier, I have never found a bulb to be the actual
stated CCT. All except one.

I just rebuilt my light bleaching set-up and purchased a $120, 250 W,
Metal Halide "Hostile - Blue" lamp (Eye Lighting, Japan) that outputs
6530 K +/- 35, with 16500 Lux, about 20" from the bulbs; less than 1
hour old. As one would expect, it is a bit spiky, but not as bad as
normal Metal Halide lamps. They label it 6500K in the PDF;
http://www.eyehortilux.com/blue.html; PDF <EQS-N-52-78-57799[1].pdf>.
Tim Vitale

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Andrew Rodney
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« Reply #12 on: June 21, 2013, 11:25:22 AM »
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That means that the PAR lamp puts out a full spectrum (spectral power distribution or SPD) of daylight with a color temp of 3500ºK. Yes, that's 2000ºK less than 5500ºK, but the spec says 3500ºK.

I suppose that daylight, in it's broadest sense, exists between sun-up and sun-down.

However, a brief Google provides hundreds, if not thousands, of statements that "daylight" is normally taken as between 5000K and 7500K.

However, Solux does explain how a CCT of 3500K can be considered as 'daylight' when occurring indoors between 194 and 2,153 lux.

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digitaldog
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« Reply #13 on: June 21, 2013, 11:27:56 AM »
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However, Solux does explain how a CCT of 3500K can be considered as 'daylight' when occurring indoors between 194 and 2,153 lux.

But will Franz accept that especially considering the source?
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Andrew Rodney
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« Reply #14 on: June 21, 2013, 11:42:21 AM »
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But will Franz accept that especially considering the source?

I imagine he should, provided that the CCT is what Solux says it and is within Solux's stated tolerances.

As far I can see, Frans' gripe is not about what constitutes 'daylight' which appears to be whatever anybody says it is ;-)

« Last Edit: June 21, 2013, 11:44:31 AM by xpatUSA » Logged

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Frans Waterlander
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« Reply #15 on: June 21, 2013, 12:49:49 PM »
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Andrew wrote: "Why don't you find out what instrument they used, the software used, and the exact testing process used to get their numbers?"

Come again? I suggested, several times, that you work with SoLux directly as you know what your test setup and method are and SoLux knows theirs. And yes, I think you have an obligation to at least try to resolve this issue since you and others are so eager to publish results that claim the products don't meet published specifications. That's a big deal in my book.
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digitaldog
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« Reply #16 on: June 21, 2013, 01:00:06 PM »
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Andrew wrote: "Why don't you find out what instrument they used, the software used, and the exact testing process used to get their numbers?"
Come again? I suggested, several times, that you work with SoLux directly as you know what your test setup and method are and SoLux knows theirs. And yes, I think you have an obligation to at least try to resolve this issue since you and others are so eager to publish results that claim the products don't meet published specifications. That's a big deal in my book.

Franz, I don't care, and only you dismiss other's data that correlates and disproves Solux marketing. Only you thus far have measured data that correlates somewhat closely with them, using a pretty piss poor product to do so. You asked a question here yourself: Do SoLux bulbs meet color temp specs? They do not. Multiple people have told you this. At PhotoNet, you suggested we measured the Solux incorrectly didn't you? Since you don't have the proper equipment anyway, and since you don't know how Solux did their measurements, how as an 'engineer' can you suggest Robin, Tim and I all did this incorrectly? We are very secure in our findings. IF you or Solux don't agree, and you've said that in print, it is up to you to prove the data collected is incorrect and you haven't done this. On the other hand, several of us, using Spectrophotometer's that range from a few thousands dollars to one over $13K all have data which suggests YOU and Solux are the one's off here. But none of us care, only you have come to no less than three sites to suggest the values Solux uses are correct and worse, that we should all be using their 5000K bulbs and then calibrating our differing displays using differing instruments to 5000K which doesn't wash.

I'd be happy to work with Solux if they want to pay me to do so. Otherwise, based on the data I and other's have collected, I have no reason to go any further. You on the other hand don't seem to be satisfied until someone, somewhere tells you they came up with the same data you did, and maybe with something like a 10 year old Minolta color meter, they will. You'll probably not find them here or on the CS list, folks here are a bit more sophisticated in terms of the equipment and testing methodology they used to come to conclusions.
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Andrew Rodney
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« Reply #17 on: June 21, 2013, 01:03:23 PM »
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And yes, I think you have an obligation to at least try to resolve this issue since you and others are so eager to publish results that claim the products don't meet published specifications.

And YOU have an obligation to prove at least three of us who all produced similar results are wrong as you stated at PhotoNet! You haven't done this and I don't think you can. You are the one who asked about the differences, not myself, or Solux. The obligation is entirely on you!
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Andrew Rodney
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« Reply #18 on: June 21, 2013, 01:07:35 PM »
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You have a career in electronics?! OH JOY!

Could you R&D and design decent MR16 circuitry into a task lamp whose 110v>12v power converter won't crap out after 40 hours of use? I mean could ya'?! REALLY?! Could ya?! That would really help a small group of photographers out who bought a Solux bulb but can't find reliable lamps to drive it.

No need to candy-coat it, Tim, let's really pound on the noob til he goes away . . .
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digitaldog
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« Reply #19 on: June 21, 2013, 01:10:49 PM »
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No need to candy-coat it, Tim, let's really pound on the noob til he goes away . . .

Tim's over on PhotoNet so he's aware of the various issues with Franz if you will. If you really want to know the various rabbit holes we've been down, there's this:

http://photo.net/digital-darkroom-forum/00bjDL

When that got as far as it did, he started this post there (and here and on the ColorSync list):

http://photo.net/digital-darkroom-forum/00bkvN
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Andrew Rodney
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