{"id":901,"date":"2008-08-06T13:52:58","date_gmt":"2008-08-06T04:52:58","guid":{"rendered":"https:\/\/regex.info\/blog\/2008-08-06\/901"},"modified":"2008-08-06T13:52:58","modified_gmt":"2008-08-06T04:52:58","slug":"why-does-brightness-wash-colors-to-white","status":"publish","type":"post","link":"https:\/\/regex.info\/blog\/2008-08-06\/901","title":{"rendered":"Why Does “Brightness” Wash Colors to White?"},"content":{"rendered":"\n\n
<\/a>\nNikon D200 + Nikkor 70-200mm f\/2.8 @ 200 mm — 1<\/sup>\/<\/big>2000 sec, f<\/span>\/4, ISO 500 —\nmap & image data<\/a> — nearby photos<\/a><\/span>\nThere is No Yellow in this Flame<\/span>\n<\/div>\n\n
<\/a>\nNikon D200 + Nikkor 70-200mm f\/2.8 @ 200 mm — 1<\/sup>\/<\/big>250 sec, f<\/span>\/5.6, ISO 400 —\nmap & image data<\/a> — nearby photos<\/a><\/span>\nThere are no White Highlights in this Flower<\/span>\n(but there is a cricket<\/span>)<\/span>\n<\/div>\n\n
<\/a>\nNikon D200 + Nikkor 17-55 f\/2.8 @ 20mm — 1<\/sup>\/<\/big>30 sec, f\/4, ISO 500 —\nmap & image data<\/a> — nearby photos<\/a><\/span><\/span>\nThere is Absolutely no White in this Display<\/span>\n<\/div>\n\n

I was a bit off the mark in yesterday's post about color limitations<\/a>, where I\nplaced<\/span> the blame for the lost color detail completely on current imaging\ntechnology, when in reality much of the blame should have been placed on\nthe consumer-level LCD in my MacBook. When I'm not traveling, I'm used to<\/span>\nusing a much<\/span>-higher-quality Eizo monitor<\/a>, and I simply<\/span>\nforgot that I wasn't<\/span> anymore.<\/p>\n\n

Perhaps I'll be off the mark with today's post as well, but yesterday's\npost reminded me of something that bothers me a lot<\/span> while I'm\npost-processing my photos in Lightroom and Photoshop: increasing brightness\nlowers saturation, driving all colors eventually to white.<\/p>\n\n

\n
“Color” vs.<\/i> “Chromaticity”<\/center>\n\n

In casual conversation, “chromaticity” can be replaced by “color”, but\n they're\n really quite different. Chromaticity refers to a physical<\/span> state (a specific<\/span>\n relative mix of light frequencies), while color refers to our human\n interpretation of those waves, and that interpretation is strongly\n dependent on context.<\/p>\n\n

For example, lights that might be considered\n white and orange in one context may well be considered dark gray and brown\n in another, brighter context.<\/p>\n\n

So, changing the brightness of a light<\/span> can change its color, but its chromaticity stays the same.<\/p>\n <\/div>\n\n\n

In the real world, red that's bright is bright red<\/b>, not<\/i>\npink or white. In the real<\/span> world, increasing brightness does not change the\nchromaticity of light – it doesn't lower the saturation, or “wash\nout” the color. But in Lightroom<\/span> and Photoshop, increasing brightness\ninexplicably pushes everything toward white.<\/p>\n\n

I understand the limitations with image sensors and film, that if you\noverwhelm them with photons, white will be registered. I also understand<\/span>\nthat if you blow out one or two of the color channels, the end result will\nbe a color<\/span> skewed away from the blown-out channels. These are sensor-level\ntechnological limitations, and although are similar to the effect I'm\nposting about, are not really related.<\/p>\n\n

In each of the photos above – from posts about a Shinto rite<\/a>, a blue light display<\/a>, and flowers<\/a> in the back yard\n– I see<\/span> generally proper colors when I lower<\/span> the exposure\/brightness\nfar enough. That means that the chromaticity has been recorded properly, so I\ndon't<\/span> understand why, when I return<\/span> the brightness to its proper level, the\nproper colors are replaced by white, or by some color leading to white\n(e.g. the orange by yellow, in the flame).<\/p>\n\n

I suppose<\/i> there is some value, for someone, in mimicking the ill\neffects of sensor limitations, so that if you increase the exposure in\nLightroom, you get the same washed-out effect as you would had you\nincreased the exposure while taking the shot, but this seems dubious as a\ndefault<\/span> operating procedure.<\/p>\n\n

So, if washing out to white is not the answer, what do I think<\/span> is? Well,\nnow we have arrived at the crux of the problem. You can't do what you want\n(increase the brightness indefinitely) due to the same image-encoding\nissues mentioned in my post\non HDR<\/a>, and in my series on digital image\ncolor spaces<\/a>. So, what can you do?<\/p>\n\n

One idea is that a color becomes locked once a color<\/span> channel has maxed\nout. This could lead to ill effects as some pixels stop getting brighter as\nthe exposure is increased, while those surrounding it continue to get\nbrighter.<\/p>\n\n

A next step to try to mitigate that problem is to have changes in\nbrightness make less and less effect as pixels come closer and closer to\nmaxing out one of their channels. This would sort of mimic what Lightroom's\n“brightness” control already does for a pixel's<\/span> three-channel combination:\nit has less and less effect the closer a pixel<\/span> already is to white. (That's\nhow the “brightness” control differs from the “exposure” control.)<\/p>\n\n

It may well be that I'm all wet, and that either of these techniques\nwould result in disjointed effects worse than what we already have, but I\ndon't<\/span> think so, at least not always. Consider the following image, from a\ndifferent post<\/a> about\nthe same light display:<\/p>\n\n

<\/a>\nNikon D200 + Nikkor 17-55 f\/2.8 @ 17mm — 1<\/sup>\/<\/big>15 sec, f\/4, ISO 500 —\nmap & image data<\/a> — nearby photos<\/a><\/span><\/span>\n<\/div>\n\n

The middle section of the display was a mix<\/span> of blue and white lights,\nbut the outer two sections were pure blue (so pure and so intense that it\nactually became a bit<\/span> painful to be there after a while<\/span>). In the original<\/span>\nversion of that photo, all three sections looked the same – a mix<\/span> of\nwhite and blue – due to a combination<\/span> of sensor limitations and the\nwashout-to-white effect.<\/p>\n\n

In Photoshop, I painted<\/span> back blue where there was white in the two side\nsections, and the result was horribly posterized. But when I<\/span> eased it back\na bit<\/span> – effecting my second idea above – the result was not\nperfect, but it was much better. That's the version you see here.<\/p>\n\n

As I said, it may well turn out that these ideas are more utopian than\npractical, but I'd like the opportunity to find out, so I hope<\/span> for a\n“chromaticity-preserving brightness” control in Lightroom.<\/p>\n\n\n","protected":false},"excerpt":{"rendered":"

I was a bit off the mark in yesterday's post about color limitations, where I placed the blame for the lost color detail completely on current imaging technology, when in reality much of the blame should have been placed on the consumer-level LCD in my MacBook. When I'm not traveling, I'm used to using a much-higher-quality Eizo monitor, and I simply forgot that I wasn't anymore.<\/p>

Perhaps I'll be off the mark with today's post as well, but yesterday's post reminded me of something that bothers me a lot while I'm post-processing my photos in Lightroom and Photoshop: increasing brightness [...]","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,1],"tags":[],"_links":{"self":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/posts\/901"}],"collection":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/comments?post=901"}],"version-history":[{"count":0,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/posts\/901\/revisions"}],"wp:attachment":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/media?parent=901"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/categories?post=901"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/tags?post=901"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}