Talk:Middle gray

Absolute *whiteness*?

The table says absolute whiteness. Shouldn’t that be, as seems to be the case elsewhwre on the page, absolute neutral gray? 174.89.73.243 (talk) 12:44, 10 February 2016 (UTC)

It should probably say Linear Arithmetic, as there the article appears to be attempting to explain that 50% is the reflectance value one obtains if one naively divides 100% (that "absolute whiteness" : perfect reflectance value) by two. i.e. If one derives a logical, although not very useful or perceptually relevant, reflectance value for "mid grey" by calculating the linear (arithmetical) mean of 0 and 100. A rather minor concern however, as the "article" is a disgrace in its entirety: A mess of mostly unreferenced misconceptions, mistakes and gibberish. Someone with some knowledge of the subject and nothing better to do needs to re-write it. — Preceding unsigned comment added by 47.232.225.116 (talk) 12:33, 4 July 2020 (UTC)

About the tone demonstration box on the top-right

Because the article itself uses white as a background colour, the box allows us to compare the tone only against white, but not against black. But the point of being a middle grey is to be in between black and white, and the demonstration should allow us to compare the tone against both. — Preceding unsigned comment added by 80.114.146.117 (talk) 18:19, 19 January 2017 (UTC)

Makes sense. — Preceding unsigned comment added by 77.61.180.106 (talk) 15:47, 24 March 2021 (UTC)

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About the "Table of middle grays"

What is your source for the 18% gray card information? Did you arrive at the values empirically? By definition the 18% gray card should have a reflectance of 18%, whiteness = 0.18 and srgb = 0.4614, similar to the row labeled L*a*b, for an L* = 0.50 (D65, 10-deg). Is your 20% value based on a white point of 90% (0.18/0.90 = 0.20)? If so, it might be nice to foot note your calculation. Bz60zd (talk) 22:50, 2 July 2018 (UTC)

One might well presume so. Unfortunately no reference or explanation is offered for why 18% is misrepresented as 20%. I think, from vague memory, the conversion of 18 to the less accurate but more precise 20 originated with either Ansel Adams or the Kodak company? — Preceding unsigned comment added by 47.232.225.116 (talk) 12:44, 4 July 2020 (UTC)

I think the 20% figure is just wrong. At least Kodak claims their grey cards have 18% reflectivity. I think the source of the confusion is that 18% is a fifth of the 90% reference white that's often found on the reverse of the grey card. — Preceding unsigned comment added by 77.61.180.106 (talk) 17:27, 26 March 2021 (UTC)

About CSS px and device pixel mismatch and the resulting problems

According to some statistics I found online, the following ratios are currently common:

1	76,54%
2	13,13%
1¼	3,88%
3	1,92%
1½	1,85%
Other	2,69%
Total	100,00%

Considering how common faulty image interpolation is, that means the test pattern image may appear too dark for 23% of our readers. Is there anything we can do? Can we possibly create a CSS test pattern for example? Because as it stands I'm wondering if it's wise to show the test pattern at all... — Preceding unsigned comment added by 77.61.180.106 (talk) 10:29, 24 March 2021 (UTC)

Okay, I've tried CSS to create a checkerboard and it doesn't really work. Although my own display shows 1-pixel checkerboards correctly, I've read online that especially on analogue display connections they don't. I think even the 2×1-pixel checkerboard in the article might not work for everyone, so I went for a 4×1 pattern, which still might not work for everyone, but that's the closest I'd want to push it and even then as one zooms one simply experiences light and dark bands really. There's no CSS unit for device pixels and if there were, I bet the wiki software would strip it, so that isn't an option either. Having the entire thing as an image link doesn't work either, because both the browser and the wiki image viewer display it based on the current zoom / pixel ratio. I don't see a solution and I think the best thing to do is to just remove the pattern image. Maybe we can put in a link to an external site with a pattern image that uses JavaScript and devicePixelRatio instead. — Preceding unsigned comment added by 77.61.180.106 (talk) 14:40, 24 March 2021 (UTC)

How about this? https://jsfiddle.net/0hvec4gd — Preceding unsigned comment added by 77.61.180.106 (talk) 16:28, 24 March 2021 (UTC)

Another problem with the black and white checkerboard pattern is that not all displays can show pure black, so instead of black it will show essentially a light grey, making the pattern appear lighter than it should. So rather than using black and white, the pattern should be using a carefully tweaked dark grey and light grey combination. I haven't updated the fiddle yet to reflect this. — Preceding unsigned comment added by 77.61.180.106 (talk) 09:56, 25 March 2021 (UTC)

I've used the following code to find two suitable greys to use:

function ginv(u){return u<=0.04045?u*25/323:Math.pow((u*200+11)/211,12/5)}
function g(u){return u<=0.0031308?u*323/25:(Math.pow(u,5/12)*211-11)/200}
Array.from({length:256},(x,u)=>Math.round(g(1-ginv(u/255))*255)).map((x,u)=>[u,x,(ginv(u/255)+ginv(x/255))/2]).sort((a,b)=>Math.abs(a[2]-.5)-Math.abs(b[2]-.5)).map(x=>x.join("\t")).join("\n")

I propose using sRGB greys 70 and 248. — Preceding unsigned comment added by 77.61.180.106 (talk) 16:26, 25 March 2021 (UTC)

I've updated the fiddle: https://jsfiddle.net/m0n3b2wc — Preceding unsigned comment added by 77.61.180.106 (talk) 17:31, 25 March 2021 (UTC)

Actually, the code above gives two shades that average to 50% linear grey. But the user won't be comparing it to that, but to the provided background colour, which will be slightly off because of rounding. So to be really accurate the code above should be changed like this:

function ginv(u){return u<=0.04045?u*25/323:Math.pow((u*200+11)/211,12/5)}
function g(u){return u<=0.0031308?u*323/25:(Math.pow(u,5/12)*211-11)/200}
[187,188].map(s=>ginv(s/255)).map(l=>Array.from({length:256},(x,u)=>Math.round(g(l*2-ginv(u/255))*255)).map((x,u)=>[u,x,(ginv(u/255)+ginv(x/255))/2]).map(x=>{var s=g(x[2])*255,r=Math.round(s),l=ginv(r/255),d=Math.abs(x[2]-l);return x.concat(s,r,l,d)})).reduce((s,a)=>s.concat(a)).sort((a,b)=>a[6]-b[6]).map(x=>x.join("\t")).join("\n")

I think 28 is a bit too close to 0 and 88 too far away. How about 76 and 246 averaging to 187? That would yield a distance of .000006, which is better than .003. I've updated the fiddle: https://jsfiddle.net/L47ysmtw — Preceding unsigned comment added by 77.61.180.106 (talk) 01:52, 27 November 2021 (UTC)

CIECAM02

Missing: 50% grey levels in newer colour appearance models such as CIECAM02. — Preceding unsigned comment added by 77.61.180.106 (talk) 18:28, 24 March 2021 (UTC)

Hmm, 77.61.180.106 added two patches for the CAMs. The issue though is that these colors are specified with TRANSPARENCY -- what is going on here? And we do have standard viewing conditions in CAM02-UCS. Artoria2e5 🌉 11:00, 29 March 2023 (UTC)

sRGB columns

Do we really need so many sRGB columns in the table? In the end, sRGB is just a colour encoding scheme, it has little physical or perceptual significance. The last column is useful to actually show the greys, but I don't see the use of the others. And if you did somehow need those values, you're enough of a specialist to do the conversion yourself. — Preceding unsigned comment added by 77.61.180.106 (talk) 18:37, 25 March 2021 (UTC)

Arguably, it has a rather large cultural significance, being the default colorspace in a vast array of applications including HTML/CSS colors. Spidermario (talk) 21:00, 25 January 2023 (UTC)

I'm not happy about the article's preferential treatment of LAB either, considering that it's 45 years old and rather outdated. I think it's time to take the gardening shears to the article. :-) But that does mean we'll have space for some extra columns in the table... how about maybe year of introduction, or lightness on black, 18% or white in a newer CAM? — Preceding unsigned comment added by 77.61.180.106 (talk) 23:59, 15 April 2021 (UTC)

No reaction for over a year, so I take it there are no complaints. I will take those columns out and perhaps see if I can think of something useful to replace them with. — Preceding unsigned comment added by 92.67.227.181 (talk) 14:22, 28 May 2022 (UTC)

Gamma column

After removing all the invalid gammas only the old Mac gamma and the trivial case were left, so there was no longer any point in keeping it.

But taking a step back, what use could this column have been anyway, even in an ideal world where simple gammas described all transfer functions? What are gamma values used for? To convert between simple gamma compressed colour spaces. So if your colours were in colour space A and you wanted them to be in colour space B, you'd combine the gammas. But if you're in that scenario would you type ‘Middle gray’ in the search box? No. You'd open your graphics application and change the colour space. Or if you're a programmer writing a graphics application, you'd look up the articles for the colour spaces you want to support and code the transfer functions.

In what scenario would you look up ‘Middle grey’ with the intention of performing a calculated brightness change? Not if you just think your picture isn't pretty enough, you'd just tweak the curves manually or fire up your HDR tool. You'd do it only if there's an area in the picture that you definitively know should be middle grey. Maybe there's a test card in the picture. And you absolutely require it to be correct, regardless of how pretty or ugly the resulting image will be. Maybe it's a scientific image. Well, I feel scientists can take care of themselves. But in that case, you'd first check to see if whatever caused the problem didn't cause other problems that require a reshoot. Was the reference light okay? Were no unexpected non-linearities introduced? Then you'd use a graphics application to convert to linear light, scale and convert back. You wouldn't bother with gammas yourself and you'd only consult this article if you'd forgotten the exact figure for the brightness of middle grey. — Preceding unsigned comment added by 77.61.180.106 (talk) 01:44, 26 March 2021 (UTC)

1903

Quoth the article: As early as 1903, middle gray was defined

However, through a careful reading of the cited source a different picture emerges. The authors drew for their understanding of the topic substantially on Grundzüge der physiologischen Psychologie by Wundt, which I have also consulted. The figures they give are part of a calculation example, probably inspired by an experiment described on page 374 to determine the relative brightness of black pigments compared to white cardboard, to illustrate the then common understanding under scientists, though not, presumably, among their audience, that our experience of lightness falls on a logarithmic scale. This is also the underlying principle of the Zone System by Ansel Adams. On a logarithmic scale, there can be no absolute middle grey, but you can determine a middle grey between two arbitrary tones in the way described. It's important to stress however that it's clear from the exactness of the figures that it's just a calculation example, the authors were encyclopaedists and didn't do any experiments themselves. Had they done so, they would have made a surprising discovery! — Preceding unsigned comment added by 77.61.180.106 (talk) 15:10, 30 March 2021 (UTC)

The checkered image doesn't render correctly.

The image included by the following syntax:

<span style='image-rendering: pixelated'>[[File:Black-white-1px-checkers.svg]]</span>

Will actually be formatted by the wiki syntax renderer using a src and srcset like this:

//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Black-white-1px-checkers.svg/50px-Black-white-1px-checkers.svg.png
//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Black-white-1px-checkers.svg/75px-Black-white-1px-checkers.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Black-white-1px-checkers.svg/100px-Black-white-1px-checkers.svg.png 2x

This means that on a 144 pixels per inch device, the image 75px-Black-white-1px-checkers.svg.png will be shown. (And that in this case ‘image-rendering: pixelated’ won't do anything.) You can look at that image and easily convince yourself that it can't have the right average brightness: in the centre, about half of the pixels is black, a third grey and a sixth white, and near the top and bottom edges about a third is black, a third dark grey and a third white, giving an appearance that is far too dark overall.

I've hacked the srcset away to see what would happen, and the result is alternating vertical bands that are far too bright and far too dark, making it hard to judge the proper grey level. The reason for this is that within such a vertical band, the ‘image-rendering: pixelated’ consistently duplicates the white or black pixels while picking the other only once.

But even on a 96 pixels per inch device it may not show up correctly, because displays often don't like such sudden black / white transitions. This is why gamma correction utilities tend to use horizontal lines only. Near the transition the colour may be just a tad dark or light and when this happens it tends to be consistently skewed in the same direction. — Preceding unsigned comment added by 77.61.180.106 (talk) 16:55, 20 May 2022 (UTC)

Additionally, the black and white checkers use absolute black and absolute white, which isn't a good idea, see ‘Another problem’ above. I just checked using Paint what happens when the checkers are shown pixel-for-pixel on my primary display and the result is too light, because the black checkers appear subtly grey due to LCD limitations.

Also note that where I typed ‘inch’ above you should read ‘logical inch’ and that 1.5x and 2x aren't zoom levels, but factors between the device pixel density and the CSS ‘pixel’ density which is always 96 CSS ‘pixels’ per inch (see §4.8.17 of the HTML5 specification). The zoom level of a device is the size of a logical inch (or logical centimetre) measured in real inches (or real centimetres). Displays are often zoomed, e.g. because people tend to sit further away from their monitor than the distance at which they'd normally hold a book or magazine. — Preceding unsigned comment added by 77.61.180.106 (talk) 05:06, 21 May 2022 (UTC)

Munsell

In light of the discussion at Talk:Lightness#Comment about the V versus Y bit I don't think the theoretical Munsell value should be in the table without at least some sort of footnote or something. — Preceding unsigned comment added by 92.67.227.181 (talk) 12:26, 30 May 2022 (UTC)

Also, when I read the History section I come away with the impression that Munsell chose his greys subjectively and that it was then discovered that these subjective greys fall on a parabola, but I conclude from Priest, Gibson & McNicholas 1920 that he used a photometer to set his values and that their experiment just confirmed Munsell chose a parabolic rather than a linear relationship. — Preceding unsigned comment added by 92.67.227.181 (talk) 14:23, 30 May 2022 (UTC)

Also, since this article deals with the actual grey level that's considered the middle, rather than with the precise curve, it's relevant that on 2 June 1899 Munsell gave a table of logarithmic grey levels (which curiously went to 11), but one where the level 5 grey[see below] had essentially the same luminosity as on his later scale. He also clearly marked this 5 level in a diagram two pages earlier, so it must have been important to him. Maybe he experimentally determined this value and its closeness to the square root of two inspired him to use a parabola? — Preceding unsigned comment added by 92.67.227.181 (talk) 12:02, 6 June 2022 (UTC)

After reading the material I discussed below, going back and re-reading, I want to clarify some points. 1) To avoid confusing whoever might read this, the level 5 grey in this table is at 50% luminosity, not sensation, and where I typed ‘luminosity’ I should have typed ‘value’ or ‘sensation’. I'm not sure what caused my error; the curve in the diary is logarithmic, but it doesn't curve the opposite way or something, it curves the same way as the later parabolic curve. So the sentence is otherwise correct; I guess I must have just typed the wrong word for some reason. (It's still irrelevant though, see point 3 below.)

2) I now think the 5 marked in the diagram just marks the halfway point of the vertical axis, even though the maximum is marked 100. The seeming correspondence is completely accidental and caused by the fact that the Pharmaceutical Era gave the value of 70 for the reflectance of paper white.

3) The table just lists some values of S = 100 log I. I don't know why, but these aren't measured values and that means the answer to the question is ‘no’. It seems the similarity between this table and his later curves is purely a coincidence. (It is not entirely coincidental that log x kind of follows √(x/10) for a bit, it has to do with the Taylor expansion of 10ˣ at log 20 – 2log ln 10, but it is a coincidence that the exponent Munsell ended up finding was 2.)

4) The 1901 diagram discussed below is based on measurement. In it, there's a two-sided arrow connecting area = 25 with stimulation = 24, so you'd think the answer to the question might be ‘yes’ after all... but no, it's Bigelow's prodding in 1905 that does it.

This post was a question, not an observation. As it turns out it had no good basis, but I'm still glad for it because it prompted me to read the rest of the diary entries.

Munsell was considering the use of a parabolic curve much earlier than 1906. On 18 February 1901 he tabulates his measured estimates alongside ‘area’ and ‘logarithm’ values and his own values seem to agree better with the ‘area’ column. He must have noticed that himself, because he drew a diagram next to it showing not just the logarithmic curve (which he at least in 1899 still assumed to be correct) but also a ‘curve of areas of shutter’. — Preceding unsigned comment added by 92.67.227.181 (talk) 14:07, 6 June 2022 (UTC)

It's a bit surprising to me that given his 1901 table and diagram, it took Munsell five years to pose the question cited in Kuehni. But apparently he didn't prioritise finding an explicit mathematical relationship between value and luminance until a meeting with Jane Caroline Bigelow on 23 November 1904. Despite his earlier experience, Munsell sticks with the logarithmic curve and keeps referencing the Weber–Fechner law. On 20 February 1905 Bigelow questions whether a logarithmic relationship is appropriate and on 7 May 1906 Munsell poses the question cited in Kuehni: ?Should we use logarithmic curve or curve of squares? But of course that doesn't mean his thinking was settled at that date. — Preceding unsigned comment added by 92.67.227.181 (talk) 00:36, 7 June 2022 (UTC)

But sometime before 23 April 1909 he had definitively decided and he notes that Edwin Bissell Holt agrees that his ‘demonstration of the exception to Weber's law is clear’. The surrounding text also shows that Munsell's thinking about his system had settled by then and that he was already testing pre-production grey patches around the time.

18%

I've looked and looked and looked and I cannot find any reference to 18% grey cards before Munsell, Sloan & Godlove 1933 and the ones I can find are only a couple of years later. In this here article 18% is specified as the colour of a grey card but I don't think that's really what it is: it's the midway point found in the 1933 paper and grey cards tend to follow this. And Kodak at least claims the following: https://www.kodak.com/en/motion/page/gray-cards (Munsell Color is a division of X-Rite. Not surprisingly, it's the division behind the X-Rite ColorChecker: https://munsell.com/color-blog/color-reproduction-photography-printing-television-40-years-colorchecker X-Rite also owns Pantone.)

Now, to get back to the 1933 paper, four of the observers were the authors and an assistant. It would be very surprising if the rest weren't insiders as well, all people who knew what a N⁵ was supposed to look like (in its 1929 incarnation). So they were always going to get something near 18% back and the results of their experiments were largely baked into the starting conditions, if you get my drift. — Preceding unsigned comment added by 92.67.227.181 (talk) 17:08, 8 June 2022 (UTC)

To answer my own question, about three quarters of the observers were employees of the Munsell Research Laboratory. The rest were outsiders, some apparently attracted through the National Bureau of Standards, some acquaintances.

The paper discusses two experiments. The first used the method of ‘just noticeable differences’ and had six participants, all very much core insiders. They find a halfway point of 18.0 on average. I must say that their data looks altogether too ‘neat’, I would have expected more noise given the method, but the Sloan curve for example is very smooth. I'm not saying the participants were committing actual fraud, but I'm sure they must have had an idea of what the results should turn out to be, because they were all insiders, and the judgement of what is just noticeable is to some extent subjective. (I guess there is also an open question as to whether a subjective value step must always necessarily contain a fixed number of noticeable differences.)

The second experiment is more more impressive, with 14 participants. Unfortunately for the authors it finds a different result and it's surprising how close to Munsell senior's original findings the results are, like A₅ = 25.8 and A₇ = 49.2. Taking into account experimental error and the fact that the participants didn't have an absolute black and white to compare the ends of the scales to, I'd say that's roughly quadratic.

But then the authors scale the aperture numbers to convert them into values, in such a way to make the results match the previous experiment. In doing so, they essentially graft the result of the first experiment onto the sample size of the second experiment. I think that this was a deliberate act of fraud. Maybe the authors realised what the implications for commercialisation would be if a new version of the atlas were to use different codes? But maybe I'm a suspicious person... I wonder if anyone noticed at the time and what they thought?

And all of this has implications for the article, because what it currently says is technically wrong. I wonder if people actually read the references they cite when they add stuff to articles? — Preceding unsigned comment added by 92.67.227.181 (talk) 15:53, 10 June 2022 (UTC)

@implications for commercialisation: A problem with that line of reasoning is that according to Priest, Gibson & McNicholas 1920 and Kelly, Gibson & Nickerson 1943 the values did in fact change. But then I look at Sloan's curve again and the rest of it and I just cannot shake the feeling that something is wrong. — Preceding unsigned comment added by 92.67.227.181 (talk) 08:25, 13 June 2022 (UTC)