Three different color calculators can't be wrong, can they?

[frans_waterlander]

<p>When using three different color calculators to find the CCT (Correlated Color Temperature) for x=0.3545 and y=0.3713, I find basically the same value: 4744.2K, 4743.8K and 4744K. A SoLux data sheet however says that the CCT for those xy coordinates is 4700K. I've asked Kevin McGuire of SoLux for a clarification, but he hasn't responded. Can anybody shine any light on this decrepancy? (pun intended)</p>

[JDMvW]

<blockquote>

<p>When using three different color calculators</p>

</blockquote>

<p>Right off the bat, there's your problem.</p>

<p>There is a Law of Measurements:<br>

<em>n</em> meters will not agree where <em>n</em> is > 1.<br>

The practical consequence of this law is to use only one meter for any given type of measurement and experiment with how to use its particular measurements to get good results.<br>

Seriously. :|</p>

[frans_waterlander]

<p>Calculating CCT from the x and y coordinates is rather complicated and different calculators use different algorithms, resulting in slightly different answers. However, these answers should not be more than a couple of Ks apart, and the answers from the three calculators that I used are within that range. However, the SoLux CCT number is way off, by about 44K, so that begs the question that SoLux sofar hasn't answered.</p>

[Tim_Lookingbill]

<p>Could you shine some light on how this is practical for making better photographs? </p>

<p>You've already made your points clear many times in the past posting on this tired subject where the results of the discussions never gave any information for a photographer to use. </p>

<p>You've posted the same thread over at Luminous Landscape. Are you just trolling, now?</p>

[digitaldog]

<blockquote>

<p>Could you shine some light on how this is practical for making better photographs?</p>

</blockquote>

<p>He's back with another one of his Solux rabbit holes. How's that article coming you were going to comment on Franz? </p>

<blockquote>

<p>A SoLux data sheet however says that the CCT for those xy coordinates is 4700K. I've asked Kevin McGuire of SoLux for a clarification, but he hasn't responded.<br /></p>

</blockquote>

<p>And neither should we! You're confused (again). CCT is a RANGE OF COLORS. I told you that months ago. Give up, stop trying to understand this Solux/CCT nonsense. As Tim suggests, go out and make (take?) some pictures. </p>

[Tim_Lookingbill]

<p>Guess I'm sort of glad Fran posted this topic because it got JDM to post some information about measuring I hadn't considered much less known about, so there. I did learn something new and interesting. </p>

<p>Thanks, JDM. Seriously!</p>

[bebu_lamar]

to me 4744, 4743, 4744 and 4700k are the same if you are talking about color temperature of a light source. I doubt that

they can make lights that varying less than 50K in color temp. We are talking about 1 percent decrepency.

[frans_waterlander]

<p>Andrew wrote: "You're confused (again). CCT is a RANGE OF COLORS. I told you that months ago."<br /> The issue here is not if CCT represents a range of colors. The issue is that given certain x and y values, the calculated CCT value should be be consistent within a couple of Ks for the various calculation methods and not be off by up to more than 200K.</p>

[digitaldog]

 

 

<blockquote>

<p>The issue is that given certain x and y values, the calculated CCT value should be be consistent within a couple of Ks for the various calculation methods and not be off by up to more than 200K.</p>

</blockquote>

 

 

The issue is, you're confused and the values Solux claim are no more correct today than they were 2 months ago before you left here with your tail between your legs. Why are you back? It is no wonder the people at Solux continue to ignore you as should we. Don't you have something more important to do in your life than attempt to understand Solux marketing claims?

 

<p><a name="pagebottom"></a></p>

[frans_waterlander]

<p>So I'm confused when I'm interested in the underlying math and understand it to the point where I spot inconsistencies and specifications that don't add up? You know, some people, me being one of them, get a kick out of the theoretical side of photography as much as the practical side. That's for instance why I developed my own equations to calculate the depth of field; why I like to be able to calculate why you don't have to change exposure when you change your distance to the subject in daylight, but have to change it at night when you change the distance between the light source and the subject; why I like to be able to calculate how big the moon would be projected onto the sensor for a given focal lenght of the lens; why I like to understand in detail what expose to the right does and doesn't do; that kind of thing.<br>

Instead of leaving with my tail between my legs, as you assert, I've been trying to work with SoLux on the issue of their measuring methods. So far, I got some preliminary info on their test setup and as soon as I have something more definitive to report on, I'll share that with everybody.<br>

You're very welcome to make constructive contributions if possible, but otherwise go do something that is "more important" to you and let me dwell on and get satisfaction out of these kinds of activities.</p>

[digitaldog]

Franz. You've posted three separate treads here on the subject, two on LuLa and one on the CS list

asking questions, then dismissing ALL the answers given. So clearly you have some agenda. Go off, do

your own research, make your own conclusions and leave the rest of us alone, PLEASE. Anything other

than your continued push back to accept answers to questions YOU ask put you squarely into the

category of internet troll.

[frans_waterlander]

<p>Andrew, like I said before, you're very welcome to make constructive contributions to the issue at hand: how to correctly calculate CCT.</p>

[Spearhead]

<p>Can you post some images that demonstrate the photographic issues with this?</p>

[frans_waterlander]

<p>Jeff, see one of my previous posts: "You know, some people, me being one of them, get a kick out of the theoretical side of photography as much as the practical side. That's for instance why I developed my own equations to calculate the depth of field; why I like to be able to calculate why you don't have to change exposure when you change your distance to the subject in daylight, but have to change it at night when you change the distance between the light source and the subject; why I like to be able to calculate how big the moon would be projected onto the sensor for a given focal lenght of the lens; why I like to understand in detail what expose to the right does and doesn't do; that kind of thing."<br>

The issue is what I believe to be flawed information and I'm looking for people that are knowledgeable about the math involved to respond.</p>

 

[Uhooru]

<p>Frans, you should read the book "Zen and the Art of Motorcycle Maintenance". It might provide some insight. Otherwise why not try taking this to a physics, or mathematics department at the local university. Let us know what they say.</p>

[Spearhead]

<blockquote>

<p>The issue is what I believe to be flawed information and I'm looking for people that are knowledgeable about the math involved to respond.</p>

</blockquote>

<p><br />This is a site about photography. It's very clear, that point is made in numerous places. If there's no value to photographs, then it's not relevant. As Barry said, go find somewhere that is about math or physics, in person or on the web. Unless there's some value to the knowledge about photography, there's no value on this site.</p>

[frans_waterlander]

<p>Let's see; this kind of calculation is used everytime you calibrate your monitor and that's not relevant to photography? Hmmm.</p>

[Uhooru]

<blockquote>

<p>Let's see; this kind of calculation is used everytime you calibrate your monitor and that's not relevant to photography? Hmmm.</p>

</blockquote>

<p>Has it been relevant to your photography?</p>

[frans_waterlander]

<p>It is relevant to understanding how monitor calibration works, how color is quantified, how to verify specifications for lighting used in many digital darkrooms, so, yes, I think it is relevant to photography. </p>

[Tim_Lookingbill]

<p>I use this, Frans...</p>

<p>http://www.markhunter.com/writings/articles/chromaticity.asp</p>

<p>It lines up with what a Minolta CA-210 Color Analyzer measured at the factory on my LG 27" LED display and the XY numbers Photoshop shows in CustomRGB panel examining my Colormunki Display LG profile. That's two calibration devices (one of them an expensively high end color analyzer), an online XY>Kelvin calculator and Photoshop.</p>

<p>That's all I need to know. I get a screen to print match of my edited Raws and that's all I need to do. If you have something else to show that indicates I need more CCT precision, prove it.</p><div></div>

[Spearhead]

<p>I bought a calibration device recommended for a number of people here. When I print on a profiled printer, I get accurate results. I have photos (you can see them online) and shows. I can post a photo of the screen and a print and you can see that it is accurate. In fact, I just printed a few for a group show I'm in.<br>

<br />All it would take is for you to post some examples showing how different these results must be for you to think it's so important. So if it's important to monitor calibration and usage, let's see the examples.</p>

[frans_waterlander]

<p>To Tim: Mark Hunter's calculator is one of the three I use myself and the three calculators come up with answers that are very, very close (see my original post). So you and I agree that you are fine and don't need more accuracy. The issue is something entirely different in that SoLux publishes x,y and CCT data that is off by up to more than 200K. Since SoLux hasn't responded to the accuracy issue, I posted here in the hopes that others could help out.</p>

<p>To Jeff: understanding how thing work and trying to resolve what looks like a major error is important to me, although is may not be so for you.</p>

[digitaldog]

<blockquote>

<p>It is relevant to understanding how monitor calibration works, how color is quantified, how to verify specifications for lighting used in many digital darkrooms, so, yes, I think it is relevant to photography.</p>

</blockquote>

<p>No, it's not. And you're still confused so let me try AGAIN. <br>

First off, it's not relevant because the numbers are not. And you don't get that. The correct numbers are those that produce a visual match (to something like a print or another display). Your obsession with numbers of Solux bulbs is odd and unnecessary. To the point that even Solux is now ignoring your. <br>

Fact: you can take two of the same instruments, say a i1D-2 colorimeter we here would use to calibrate our displays, use two different software products to calibrate your display and you'll get different numbers. You can use the same software with differing devices and get different numbers. This is one reason why X-Rite, a company that knows a bit about instrumentation has introduced XRGA. You should read up on it. <br>

Fact: I have three $5000 iSis Spectrophotometer's and the Rev C and Rev E differ more than a dE 2000 of 1 on JUST measuring white! Fact, when you were equally confused about Solux, three of us provided numbers that were different and dismissed the values you feel need to be exact from Solux. <br>

Fact: if you want multiple numbers to reasonably match, you have to do a lot of work and spend a lot of money. Like buying multiple identical NEC Spectraview II models, the same NEC instrument and setting the values the same. Then using a reference grade Spectrophotometer, you'll STILL see tiny differences in the numbers. <br>

You are <strong>obsessed</strong> with Solux CCT values for some odd reason. Go off as other's have suggested and find a forum where anyone but you cares. You say you want feedback from readers here (and on LuLa) but just dismiss what you're told. None of the now three threads you yourself created here have anything to do with photography. None have any useful content either. Don't you have something better to do? </p>

[frans_waterlander]

<p>Andrew, who's confused here? It appears to be you. This post is about how to calculate CCT once you have the x and y values. Any calculator that uses the found x and y coordinates should come up with the same CCT value within a couple of Ks. The three calculators that I use do just that: come up with a CCT values that are very, very close. And then there is the SoLux website that comes up with CCT values that are totally out of whack and I'm looking for people that can help resolve this particular issue. So, unless you have anything to contribute to the narrowly-defined issue at hand of how to calculate CCT using x and y coordinates and why some calculators are very, very close and some (like the one used by SoLux presumably) can be so far, far off, why don't you stop bringing up stuff (like using different sensors and software) that have in essence nothing to do with the issue at hand.<br>

If I wanted to discuss why different sensors, different software, different monitors, different lamps would yield different results, then I would have stated that in the first place and that would be a totally different discussion.</p>

[Spearhead]

<blockquote>

<p>To Jeff: understanding how thing work and trying to resolve what looks like a major error is important to me, although is may not be so for you.</p>

</blockquote>

<p> <br>

OK, so you can't connect it to photography. No images, no examples, nothing. Since that's the case, it's an academic exercise that doesn't really belong in this forum.</p>