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
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?
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).
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
# 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.pdf>.