{"id":455,"date":"2008-11-13T22:27:36","date_gmt":"2008-11-14T03:27:36","guid":{"rendered":"http:\/\/blog.kenperlin.com\/?p=455"},"modified":"2008-11-14T05:32:42","modified_gmt":"2008-11-14T10:32:42","slug":"everybody-knows","status":"publish","type":"post","link":"http:\/\/blog.kenperlin.com\/?p=455","title":{"rendered":"Everybody knows"},"content":{"rendered":"

There are many things that everybody knows, which nonetheless are not true.<\/p>\n

More precisely, there are many questions you can ask of a hundred people at random, and they will all give the same answer, and that answer will be wrong.<\/p>\n

To be fair, there are people who have no opinions about things. So let’s set some ground rules: A person can opt out of answering your question – they can just say “I don’t know”, or even “I don’t even understand what you’re talking about.” In that case, you can just ask somebody else your question, and keep on going from person to person until you’ve accumulated a hundred answers.<\/p>\n

Here’s one such question: If you want to show the color black on a computer screen, you specify the color 0,0,0 (red and green and blue all zero). If you want show the color white on a computer screen, you specify the color 255,255,255 (red and green and blue all 255).<\/p>\n

But what if you want middle gray, containing half the brightness of white? What color should you specify?<\/p>\n

Just about anybody who chooses to answer this question will say something like 128,128,128 – and that’s a perfectly logical answer.<\/p>\n

But it turns out to be wrong. The right answer turns out to be “it depends”.<\/p>\n

In fact, on many computer monitors 128,128,128 will result in something considerably darker than half the brightness of full white. On my LCD screen of a Lenovo ThinkPad, half brightness occurs at around 170,170,176.<\/p>\n

What I mean by that is that if you make a fine checkerboard pattern where half the pixels are black and the other half are white, and you compare this with a solid color, on my computer you need to set the solid color to around 170,170,176 to get the same overall visual brightness.<\/p>\n

You’ll probably get somewhat different results on your computer monitor, but you can see the general idea for yourself. Look at the following image and squint, so that you can’t really see the details of the checkerboard. On my computer screen the solid gray areas look pretty close to the average shade of the checkerboard:<\/p>\n


\n
\n
\nblack\/white checkboard versus 170,170,176<\/i>
\n<\/center><\/p>\n

\n <\/p>\n

In contrast, on my computer 128,128,128 produces something waaaay too dark:<\/p>\n


\n
\n
\nblack\/white checkboard versus 128,128,128<\/i>
\n<\/center><\/p>\n

\n <\/p>\n

Of course, on your computer screen the second one might look right. The “correct” answer varies from screen to screen.<\/p>\n

This means that lots of people who make images with computers are getting things very wrong. They think that to make something half as bright as white they always need to use 128, and to get a quarter as bright as white they need 64, and so forth. If you ever wonder why so many computer graphic images have an odd “fake” look, that’s one of the reasons.<\/p>\n

Can anybody think of something else that “everybody knows”, where the conventional wisdom is wrong?<\/p>\n","protected":false},"excerpt":{"rendered":"

There are many things that everybody knows, which nonetheless are not true. More precisely, there are many questions you can ask of a hundred people at random, and they will all give the same answer, and that answer will be wrong. To be fair, there are people who have no opinions about things. So let’s … Continue reading “Everybody knows”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=\/wp\/v2\/posts\/455"}],"collection":[{"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=455"}],"version-history":[{"count":0,"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=\/wp\/v2\/posts\/455\/revisions"}],"wp:attachment":[{"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=455"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=455"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.kenperlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=455"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}