Talk:Lightness

merge from value

These describe the same color attribute, and "lightness" is the term which is coming to be used in modern models like CIELAB and CIECAM. The value article should be merged into this one, and then redirected here. --jacobolus (t) 20:02, 19 September 2007 (UTC)

Value is an extremely relevant term in drawing and painting, and it shows no signs of falling into disuse. I believe "lightness" has more industrial connotations, whereas "value" still applies to the fine arts. -bornon5, 31 October 2007 —Preceding unsigned comment added by Bornon5 (talk • contribs) 02:53, 1 November 2007 (UTC)

That's fine. The article can explain that both words are used for the concept, and the value article can redirect here. The point is that we have a single concept, so it's silly to duplicate the information about it on two different articles. The popularity of the term "value" comes mostly from Munsell's use, as far as I know. More recent models like CIELAB and CIECAM02 use the term "lightness". --jacobolus (t) 04:24, 1 November 2007 (UTC)

Comment. Is the term value used in painting to mean something not covered in the value article? If we mean that lightness=value=correlate of perceived brightness, I'm for merging them.--Adoniscik (talk) 14:58, 3 February 2008 (UTC)

Does value mean something different in painting than its use by Munsell? I'm not aware of what that definition is. --jacobolus (t) 22:10, 3 February 2008 (UTC)

I just checked a bunch of books, and they appear to agree that value is lightness or something reasonably equivalent. For example, this one. And this one pretty much says that artists use the Munsell system. Dicklyon (talk) 00:43, 4 February 2008 (UTC)

Any objection to the merge? Dicklyon (talk) 01:16, 4 February 2008 (UTC)

Objection. —Preceding unsigned comment added by 24.111.103.220 (talk) 06:15, 7 February 2008 (UTC)

I agree with the merger. However, HSV should be mentioned as an unusual case, as colors don't progress from black to white. SharkD (talk) 10:16, 7 February 2008 (UTC)

What is the diagram?

Could someone please add caption text to the first image (ColorValue.jpg)? —Preceding unsigned comment added by 79.176.137.250 (talk) 16:48, 28 November 2008 (UTC)

Some problems with the previous version

"Various color models have an explicit term which places the color on a scale from utter black to pure white. The HSV color model and Munsell color model have an explicit value, while the HSL color model uses a related parameter called lightness instead."

The "explicit value" of HSV refers to something different; i.e. the value/color is not "on a scale from utter black to pure white." The HSL parameter lightness is the one that's closer to the Munsell system.

"In the HSV and Munsell color models, a color with a low value is nearly black, while one with a high value is the pure color."

This is not true of the Munsell system. HSV is the oddball here. It also contradicts the first sentence I quoted.

As for the rest of the article, it was in need of cleanup (forming paragraphs out of loose sentences, etc.) You were right in that I deleted a good bulk of stuff on accident. SharkD (talk) 06:19, 29 June 2009 (UTC)

Also, the rescaling of the second image is ugly; it's hardly legible. This is a software issue however. SharkD (talk) 06:27, 29 June 2009 (UTC)

Further, in the image, it might be a good idea to put the word "luminance" somewhere on the x-axis. It's explained in the caption, but it might not be enough. SharkD (talk) 06:33, 29 June 2009 (UTC)

Tone

Tone (disambiguation page) links to Lightness (color), but the article never uses the word "tone", and I don't think they're at all synonymous. Anyone care to clear it up? —Pengo 12:12, 20 July 2009 (UTC)

Tone is a term that was traditionally used in black-and-white photography for this concept, at least since the early 20th century. See tone mapping (not a great article, but a start). Or here is an old book example. And here is one that compares "Tone" to "Value" explicitly. Dicklyon (talk) 14:52, 20 July 2009 (UTC)

Also Tone reproduction is more about the traditional use in photography. Dicklyon (talk) 18:41, 20 July 2009 (UTC)

In art, tone is a synonym for value, perhaps more common in drawing, where dark tone is built up with manual application of a dark medium like graphite or charcoal, than in painting. —Michael Z. 2012-04-22 19:19 z

Extremely convoluted article

I came here to learn about 'value' from the fine arts perspective.

The first section is hilariously wordy and inaccessible. "... is a representation of variation in the perception of a color or color space's brightness. It is one of the color appearance parameters of any color appearance model."

Would it be that absurd to just say: "It's how bright a color is."

Then, the rest of the article is just gibberish to someone, such as myself, from a fine arts background, and offers nothing of substance as to how value relates to or is used in the fine arts. This article is horrible and should be rewritten by someone who isn't copy pasting from a science textbook. — Preceding unsigned comment added by 45.47.156.179 (talk) 22:22, 30 October 2015 (UTC)

Um, yes, it would be absurd or, more to the point, simply wrong. Lightness does not equal brightness in color theory. I’m not saying the article can’t be improved – it most certainly can. But not in this way … If anything, you need more words to clearly point out the difference between lightness and brightness, as it is obviously easy to confuse them. --Uli Zappe (talk) 07:48, 11 November 2015 (UTC)

For the expert, I presume the article has much to say. For the laymen, as with so many Wikipedia articles, it is all but valueless. Perhaps that is the intent, though I would hope not. I appreciate the need for experts to express full concepts, and that they do so voluntarily is admirable. It would be even more admirable if the expert would then create a complementary article understandable by those not in the field. One does this, primarily, by avoiding undefined terms. Use the words and concepts understood by the audience and build from there, defining as one goes. Examples and illustrations in this context are very helpful. Education is not the spewing of words. It is the transmission and duplication, at receipt, of concepts. One hopes, despite evidence to the contrary, that this is the goal of Wikipedia contributors.

Ridiculous youtube reference (Brightness vs. Lightness)

The reference [1] (Brightness vs. Lightness) is to a YouTube video that describes what a guy believes that the Photoshop settings of brightness and lightness mean.

It's ridiculous, there are already several accepted discording definitions of lightness and brightness in the various fields, we really missed the photoshop one.

It discredits the whole articles of Lightness and Brightness, those who originally wrote them have no idea about these things and managed to add confusion to an area that was already fill with confusion to the brim.

(BTW I'm not really an expert, don't ask me to fix it; maybe until a real expert comes the best thing would be to delete these articles altogether)

Gabrolf (talk) 14:53, 26 January 2017 (UTC)

"Lightness means brightness of an area judged relative to the brightness of a similarly illuminated area that appears to be white or highly transmitting. Lightness should not be confused with brightness.[1]" Lightness means brightness [but] should not be confused with brightness. That's confusing. — Preceding unsigned comment added by Gitchygoomy (talk • contribs) 07:56, 17 March 2017 (UTC)

It's confusing to you because you're skipping the part of the sentence that explains the difference: ‘judged ... transmitting.’ — Preceding unsigned comment added by 77.61.180.106 (talk) 01:39, 19 June 2021 (UTC)

An approximately 18% grey card, ...

I don't like this paragraph. It seems to suggest that grey cards are commonly calibrated at 18.42% but I'm not sure that's true, or even possible. At the very least, I've found a data sheet for a Kodak grey card and it considers a tolerance of 1% ‘very tight’; the figures it gives for the front and back are 18% and 90% and the calibration graphs show that the actual reflectance is somewhat wavelength-dependent.

Furthermore, this section is about work done in the seventies. But the first mention I could find of a grey card in the photographic sense is from 1939 (Curtis) and of a standardised one from 1940 (Neutralowe). Possibly an article from 1938 (Haskell) might also count, but I feel he's using the card in a different way and it doesn't fully qualify. The first ‘modern’ middle grey was published in 1915 (Munsell) although arguably the concept was much older, e.g. Mayer 1758. Point is, even though it makes sense to introduce these terms in an article about lightness, it makes no sense to introduce them in this particular section.

In colorimetry and color theory, lightness, ..., is a representation of a color's brightness.

I think in standard terminology this isn't true, or at best only true for colour appearance models that don't account for the difference.

Comment about the V versus Y bit

FTA: Note. – Munsell's V runs from 0 to 10, while Y typically runs from 0 to 100 (often interpreted as a percentage). Typically, the relative luminance is normalized so that the "reference white" (say, magnesium oxide) has a tristimulus value of Y = 100. Since the reflectance of magnesium oxide (MgO) relative to the perfect reflecting diffuser is 97.5%, V = 10 corresponds to Y = 100/97.5% ≈ 102.6 if MgO is used as the reference.

Looking at figure 15 in Priest, Gibson & McNicholas 1920 where V² is plotted against Y with a MgCO₃ reference with a reflectivity of 0.983, it's clear that Munsell's greys are dead on a straight line through the origin. The authors offer the hypothesis that Munsell may have thought he was setting aperture areas on his photometer whereas in actuality he was setting aperture diameters, although they say the possibility that the quadratic relationship was intentional cannot be discounted because Munsell wouldn't have liked the look of a linear relationship. I personally feel that his wouldn't explain Munsell's wording in his atlas though.

(‘reply’ to myself) Yet according to Kuehni, Munsell wrote on 7 May 1906: ‘Should we use logarithmic curve or curve of squares?’ So that fact seems to strongly lean in favour of the ‘it was intentional’ hypothesis after all. On the other hand in the 1915 edition of the atlas, which I assume the 1920 paper was based on, Munsell writes ‘Chart 50 at the middle of the Color Tree bears only colors which reflect 50 per cent, of the luminosity of white’ Now, in the scan the relevant patch has Y=.253, 20% patch has Y=.043 and the 70% patch has Y=.496. (They're also slightly off-grey.) This seems to indicate that the person at the Smithsonian who calibrated the scan either didn't know about the 1920 paper and only did an internal calibration, or he did know about it but decided to compensate for Munsell's error. But anyway, the patches follow a square law, even though the text on e.g. the 50% page reads: ‘Thus R⁵⁄₉ indicates that the red upon which it is placed reflects 50% of standard white’.

A key takeaway in either case is that Munsell's greys weren't visually judged, but determined using a photometer.

Studying figure 15 some more, the intersection of the trend line with the right vertical axis catches our eye. For V=10 we find Y=95.2% compared to the MgCO₃ reference, or only 93.6% of the reflectivity of an ideal reflector! This is only slightly lighter than the 90% white reference on a Kodak grey card, but it's clear from Munsell's text that V=10 was supposed to be the unachievable ideal reflector. Munsell must have made a calculation or calibration error of some sort.

For the bit of the article that I quoted and the material below it this has the implication that, at least in the 1915 edition there was a difference between how the V scale should have been versus how it actually was in published form, which then means that the calculation shown is wrong. Same applies to the formula below, which is I think based on a (reasonable) reading of the abstract of the source but not its actual findings. Checking the recommendations section at the end of the source it may well have been an aspirational thing, because the authors recommend setting V=10 as an absolute maximum in a future edition.

The snippet from the article could, if read the wrong way, also imply that Y needs to be corrected in the way described, or at least can be corrected that way, in all the cases listed below, and that MgO is the standard reference white in the models listed. I know this wasn't intended, but a reader in a hurry might not catch that. So I guess we should just check all the sources. In the case of a physical reference white with a known reflectivity it's even possible that it's been compensated for already, like is often done in photography with the 90% reference I mentioned above.

From the Munsell article: ‘The original embodiment of the system (the 1905 Atlas) had some deficiencies as a physical representation of the theoretical system. These were improved significantly in the 1929 Munsell Book of Color and through an extensive series of experiments carried out by the Optical Society of America in the 1940s resulting in the notations (sample definitions) for the modern Munsell Book of Color.’ I think that's unnecessarily vague and seems to downplay the severity of the issue. It could also do with some inline citations.

Cube-root snippet

FTA: Neither option turned out to be quite correct; scientists eventually converged on a roughly cube-root curve, consistent with the Stevens's power law for brightness perception, reflecting the fact that lightness is proportional to the number of nerve impulses per nerve fiber per unit time.[Hunt 1957]

There are a couple of problems with this part. First, scientists didn't in the end converge on a cube-root curve. I'm not bickering here about the fact that the underlying function probably isn't really a power function but more something based on Michaelis–Menten kinetics, after all the article says ‘roughly’, but about the fact that the stated gamma isn't the current value, which is context dependent but (according CIECAM02, which is isn't quite the most current but close, and a back of the envelope computation) in the range of about 1.6 (light) to 2.1 (dark). I think the root cause that the discrepancy is so large, rather than just being a bit off due to intervening advancement of understanding, is that Hunt is talking about brightness, not lightness, which has (again, according to CIECAM02) double the gamma, so about 3.1 to 4.1.

There's also a problem of chronology. Now, I know the impersonal writing style is de rigeur in much of academia and I myself was taught to write this way, but it's usually a terrible idea and Hunt 1957 is good example where it can appear especially disingenuous. Reading that article, phrases like ‘in a paper published’ and ‘it was concluded that’ made me think initially that the findings were those of others, perhaps even crystallised ideas generally held in the field. But checking the references it's clear it's actually talking about a previous paper by Hunt himself, published in 1953. So the article basically says ‘Hopkinson's 1956 results support my model’; reading Hopkinson's reply leaves me with the impression that Hopkinson wasn't so sure. Either way, Hunt's work isn't based on Stevens's, it couldn't have been because Hunt's work predated it by four years and Hopkinson's work by half a year.

And apparently the opposite wasn't true either. The fact that Hunt 1957 and Stevens 1957 were published in the same month appears to be a coincidence. Stevens takes his brightness data from work done by Hanes in 1949. (Which probably should be mentioned in the article. Even though Hanes's work was about brightness rather than lightness it's still relevant.)

And the clumsy way the snippet from the article was phrased makes it seem like there is some direct causal connection between a perception following Stevens's law and the proportionality to nerve impulses. As far as I can tell this isn't true; Stevens's law is purely empirical. The connection between actual chemical and physical processes and sensations is currently thought to be the Michaelis–Menten model. Which also means that although Steven's work may have historical significance and should hence be mentioned in the chronology, it doesn't directly relate to current understanding and its mention in this snippet is out of place.

Now, since I've mentioned CIECAM02, I feel obliged to say that the article discusses its technicalities and the basic model, but there are still a number of parameters which need to be fitted to fix the lightness scale. What I'm saying here is that even if the model is correct, it must still be fitted to good data to get the right parameters so that the resulting whole describes human colour vision. The article should explicitly cite the studies that provided the data underlying the scale. — Preceding unsigned comment added by 92.67.227.181 (talk) 14:23, 2 June 2022 (UTC)

More chronological problems

FTA:

1. The Munsell value has long been used as a perceptually uniform lightness scale.
2. A question of interest is the relationship between the Munsell value scale and the relative luminance.
3. Aware of the Weber–Fechner law, Munsell remarked "Should we use a logarithmic curve or curve of squares?"
4. Priest et al. provide a basic estimate of the Munsell value (with Y running from 0 to 1 in this case): V = 10√Y

I'll discuss these in order.

1. This has been true from 1915, when the first atlas was published until this gradually stopped being true in the fifties. (The reason was on the one hand that as early as in 1943 the focus started to shift from perceptual uniformity as an aim in and of itself, making backward compatibility at least a secondary aim, and the shift towards formula-based approaches.)
2. Shortly after 1906 Munsell decided to use a parabolic scale because he thought that would yield a visually uniform scale. The greys in his 1915 atlas lie smack bang on a parabola.
3. This was in 1906, before his atlas was published. It isn't true that the greys in the atlas were tweaked visually and a parabola was post facto considered a good match for them. Rather, the greys were set to fall on a parabola with the help of a photometer.
4. This isn't a ‘basic estimate’. The 1920 article's goal was to show what relationship between Y and V Munsell used. It was already known Munsell had used a photometer to arrive at his greys. Looking at the graph in the 1920 article it's clear that Munsell had worked accurately, although his reference grey, which should have been an ideal 100% reflector, was in reality more like 93.6%. (This discrepancy has apparently never been fully explained.) In theory this formula should hold exactly if one uses the same reference Y as Munsell did, although there are limits to how accurate paint can be mixed.

So yeah, the article jumps backwards and forwards in time and gets causality wrong. — Preceding unsigned comment added by 92.67.227.181 (talk) 01:10, 3 June 2022 (UTC)

1996

In 1996 Hård, Sivik & Tonnquist published experimental results that are relevant to the article. — Preceding unsigned comment added by 92.67.227.181 (talk) 16:56, 11 June 2022 (UTC)

1933

FTA: Munsell, Sloan, and Godlove launch a study

When you say ‘launch a study’ you implant an image in the reader's mind of about a hundred participants, government funding and oversight, that kind of thing. But the study that their formula was based on was just them and a couple of employees saying how many brightness differences they just about noticed between reflectance steps. They didn't show if that would be a good measure for brightness, I don't know if they were biased, I don't even know if they were lying or even if Munsell, Sloan & Godlove reported truthfully on the findings.

The second study they did had fourteen participants, some of them outsiders, and they essentially confirmed Munsell's original parabolic curve. To within experimental error, I'd say. Which of course doesn't mean the curve ultimately is a mathematical parabola, the underlying connection might be – in fact, is – different, just that whatever curve it is, the data that was available is very well approximated by it.

The only reason we need to mention them at all is because they ultimately managed to influence CIELAB. And how did that happen!? I'm used to people adding stuff to Wikipedia not having actually read the references they cite, but how did the CIE not catch on? — Preceding unsigned comment added by 92.67.227.181 (talk) 15:29, 12 June 2022 (UTC)

Who is....

Alexander Munsell's name is used once without telling us who this is - - -

"1933
Alexander Munsell, Louise Sloan, and Isaac Godlove launch a study..."

Is this a relative of Albert Munsell or an error that is meant to be Albert? There's no Wikipedia listing for this person other than this article.

Thank you for your attention, Wordreader (talk) 23:36, 7 March 2024 (UTC)

Alexander Ector Orr Munsell (1895–1983) was Albert Henry Munsell's son. You can read Dorothy Nickerson's obituary of A.E.O. Munsell here. Albert Munsell died in 1918, so certainly wasn't doing scientific work in 1933. –jacobolus (t) 23:44, 7 March 2024 (UTC)