{"id":255,"date":"2006-10-03T17:45:30","date_gmt":"2006-10-03T08:45:30","guid":{"rendered":"https:\/\/regex.info\/blog\/photo-tech\/color-spaces-page4"},"modified":"2006-10-03T13:36:30","modified_gmt":"2006-10-03T04:36:30","slug":"color-spaces-page4","status":"publish","type":"page","link":"https:\/\/regex.info\/blog\/photo-tech\/color-spaces-page4","title":{"rendered":"Digital-Image Color Spaces, Page 4: Color Management"},"content":{"rendered":"\n\n<style type='text\/css'>\na.btn    { background-color: #555; border: solid 1px #888; padding: 2px 5px }\nspan.now { background-color: #533; border: solid 1px #888; padding: 2px 5px; font-weight: bold }\n<\/style>\n<div style='display: block; background-color: #444; padding: 7px; border: solid 2px gray'>\n<b>Article:<\/b>\n<a class='btn' href='\/blog\/photo-tech\/color-spaces-page0\/'>Table of Contents<\/a> &nbsp; &nbsp; &nbsp; <b>Page:<\/b>\n<a title='Introduction' class='btn' href='\/blog\/photo-tech\/color-spaces-page1\/'>1<\/a> &middot;\n<a title='Test Images' class='btn' href='\/blog\/photo-tech\/color-spaces-page2\/'>2<\/a> &middot;\n<a title='Color Mis-ManagementTest Images' class='btn' href='\/blog\/photo-tech\/color-spaces-page3\/'>3<\/a> &middot;\n<span class='now'>4<\/span> &middot;\n<a title='Chromaticity Diagrams'     class='btn' href='\/blog\/photo-tech\/color-spaces-page5\/'>5<\/a> &middot;\n<a title='Design Tradeoffs'          class='btn' href='\/blog\/photo-tech\/color-spaces-page6\/'>6<\/a> &middot;\n<a title='Recommendations and Links' class='btn' href='\/blog\/photo-tech\/color-spaces-page7\/'>7<\/a>\n<small>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This is the fourth page of a seven-page article<\/small>\n<\/div>\n\n<p>So far in this article, we've talked about how color spaces are used to\nrepresent colors as numbers within an image file. But once a color-managed\napplication has used the color space to convert the images colors into a\ndevice-independent understanding of color, how does the application convert\nthat to the device-<i>dependent<\/i> information needed by your monitor or\nprinter?<\/p>\n\n<p>The answer lies with the other half of color management: <b>device color profiles<\/b>... <\/p>\n\n\n<p><a name='Hardware'><b>Color Profiles for Monitors, Printers, Paper, Scanners,... ?<\/b><\/a><\/p>\n\n<p>The <a href='\/blog\/photo-tech\/color-spaces-page1\/'\nclass='quiet'>first page<\/a> of this article discusses color profiles for\ndigital images, but there are also color profiles for devices (computer\nmonitors, scanners, printers, paper, and ink). Like their digital-image\nversions, these color profiles describe how to convert between color and\nraw numeric data, but in the case of these real-world devices, the color is\nnot theoretical, but actual: how much of which ink should be applied to the\npaper to achieve the proper color, or how much energy should be used to\nfire a CRT's cathode ray against its screen's phosphors, etc.\n\n<\/p><p>\n\nWith a color-managed system where all the links of the visual chain have\nappropriate color profiles, the device-independent color data (such as\ninside an image file) can be converted with certainty to device-dependent\ncolor data such as monitor voltages or printer ink amounts.\n\n<\/p><p>\n\nHaving properly-calibrated devices, controlled by software using the\nappropriate color profile for the device, is essential to ensure that the\ncolor you see on the screen or on paper is <b>the<\/b> proper color, or, at\nleast, as proper a color as can be had within the physical limits of the\ndisplay method. (If a monitor doesn't have the physical ability to\nreproduce a particular color, no color space or color profile can change\nthat.)\n\n<\/p><p>\n\nIt's common to see complaints of &#8220;<i>the picture looks so different\nwhen I print it compared to what I see on my screen<\/i>&#8221; on\nphotography-related forums, and the reason is almost certainly related to\nthe non-use or misuse of device color profiles.\n\n<\/p><p>\n\nUnfortunately, it's not necessarily easy having a properly color-managed\nsystem.\n\n<\/p><p><b>Color-Managed Printing<\/b><\/p>\n\n<p>\n\nA color profile for a printer is dependent on the printer\/ink\/paper\ncombination, so if you print photos on several different kinds of photo\npaper, you must create several different color profiles, and be sure to use\nthe appropriate one when printing.\n\n<\/p><p>\n\nPrinter manufactures usually supply canned profiles for their printers\n(but only for use with their ink and their paper), but these can be of dubious\nusefulness. A <i>custom<\/i> printer\/ink\/paper color profile creates the most\ncertain output, but generating such a color profile can be costly.\n\n<\/p><p>\n\nOne method involves printing an image with known real-world colors, and\nsending it (and some money) to a profiling service, which uses a\nspectrophotometer to measure the actual colors you got. From this, it can\ncalculate what adjustments need to be made so that you get the truest\ncolors, and that information is encapsulated into a\nprinter\/ink\/paper-dependent color profile.\n\n<\/p>\n\n<p>There are other methods as well. <a\nhref='http:\/\/www.colorvision.com\/store_spec_pf-rightforme.shtml'>This\npage<\/a>, which is part of an advertisement for one such method, gives a\nnice overview.\n\n<\/p>\n\n<p><b>Color-Managed Monitors<\/b><\/p>\n\n<p>Creating a monitor-specific color profile is generally easier.\n\n<\/p><p>\n\nThe easy &amp; cheap method involves running a calibration program, and\neyeballing answers to things like &#8220;slide the slider until the\n<b>X<\/b> is the same color as the background.&#8221; The wildly vague\nnature of subjective human color perception makes this an iffy scenario,\nbut the result is better than doing nothing. Apple's OSX includes this with\nits Display Calibrator Assistant (System Preferences &gt; Displays &gt;\nColor &gt; Calibrate).\n\n<\/p><p>\n\nA better solution is a calibration device that you stick on the screen so\nthat it can meter the colors that its associated software sends. It can\nthen calculate a profile for your specific monitor (with its\ncolor\/tint\/brightness\/contrast settings as you have them during the test).\nTesting devices to do this run as little as $120 or so.\n\n<\/p>\n\n<p><b>Reality<\/b><\/p>\n\n<p>\n\nIt might sound like a lot of hassle to create color profiles for your\nmonitor and printer\/paper\/ink, but that's only because <b>it is<\/b>. Most\npeople don't, and even if they had the proper profiles, most software\ndoesn't take advantage of them. If only one web browser (that I know of)\neven bothers to take into account an image's embedded color profile, how\nmany do you think will then use your monitor's profile to make the second\nconversion (from true color to the best appropriate color your monitor can\nproduce)?\n\n<\/p><p>\n\nA color-managed application like Photoshop does do this properly, but most\nsoftware doesn't. Apple software for the Mac generally does, but not all\nsoftware for the Mac does. (I find it really disappointing that <a\nhref='http:\/\/www.mozilla.com\/'>Firefox<\/a> for the Mac is not a color-managed\napplication.)\n\n<\/p>\n<p>\n\nBack to images, if an image has ever been saved as sRGB, any extra color\ninformation it might have had is lost forever, even if that sRGB image is\nlater (re)converted to a &#8220;wider&#8221; color space. (<a\nhref='\/blog\/photo-tech\/color-spaces-page5\/'>Page 5<\/a> of\nthis article talks about color-space &#8220;width.&#8221;)\n\n<\/p><p>\n\nIn fact, you'll <b>lower the quality<\/b> of an sRGB image by converting it\nto a different color space, because the new color-space's discrete\nencodable colors won't match up exactly with the old space's, necessarily\nrequiring some fudging of the colors to get them to fit.\n\n<\/p><p>\n\nAnyway, the upshot is that while sRGB is still the de facto standard for\nthe web, having your AdobeRGB or other &#8220;wider&#8221; color-space images converted\nto sRGB means that you're throwing out the ability to represent shades that\nyou may well have the ability so see on a modern (properly color managed)\nmonitor or printer.\n\n<\/p><p>\n\n<span style='border: solid 1px #DEC; padding: 3px'>When I convert a photo to sRGB for web display, it's with a <i>copy<\/i> of\nthe original.<\/span>\n\n<\/p>\n<p><a name='AdobeRGB'><b>The AdobeRGB Color Space<\/b><\/a><\/p>\n<p>\n\nThe <a href='http:\/\/en.wikipedia.org\/wiki\/Adobe_RGB'>AdobeRGB<\/a> color\nspace is a popular pro\/prosumer camera alternative to sRGB. The default\nout-of-the-box color space for these cameras is invariably sRGB, but if\nsupported, AdobeRGB can be selected for new images via the camera-settings\nmenu.\n\n<\/p><p>\n\nAdobeRGB can encode a wider variety of colors than sRGB (in particular,\nricher shades of green and blue). It does this at the necessary expense of\nencoding all the colors with slightly less precision; more on encoding\ntrade-offs on <a\nhref='\/blog\/photo-tech\/color-spaces-page6\/'>page 6<\/a> of\nthis article.\n\n<\/p><p>\n\nIf you never need the richer shades of green, the slight loss of precision\ncould theoretically hurt you, but the general consensus is that AdobeRGB is\nbetter for printing than sRGB. (sRGB is still the best for the web, of\ncourse, simple because not using it risks incorrect colors.)\n\n<\/p><p>\n\nIf their camera supports AdobeRGB, many photographers avail themselves of\nit so that they maintain maximum color information. Nevertheless, many\nusers opt to stay with sRGB because its ubiquity simplifies their workflow.\nTo them, the slight improvement in color is not worth the inconvenience of\nneeding to pay attention to a file's intended use.\n\n<\/p>\n\n<p><a name='RAW'><b>Raw Images<\/b><\/a><\/p>\n\n<p>\n\nA more advanced option still, for cameras that support it, are <a\nhref='http:\/\/en.wikipedia.org\/wiki\/RAW_image_file'>Raw<\/a> image files.\n&#8220;Raw&#8221; is not a file format, but a type of data: it contains raw\nimage-sensor data, prior to any processing (such as white balance\ncompensation, sharpness adjustments, conversion to a device-independent\ncolor space, and the like). For reference, each camera maker has its format\nfor their camera's raw files: Nikon cameras, for example, create\n<tt>.NEF<\/tt> files, while Canon cameras create <tt>.CRW<\/tt> or\n<tt>.CR2<\/tt> files.\n\n<\/p><p>\n\nThe benefits to working with raw files instead of JPG are numerous, but\nbeyond the scope of this article. One benefit of note to us here, though,\nis that sensor-dependent color data in a raw file is usually much more\ndetailed than the comparable JPG, which has had the color data reduced to a\ndevice-independent color space, typically sRGB or AdobeRGB.\n\n<\/p><p>\n\nWith the advent of native raw workflow applications like Apple's <a\nhref='http:\/\/www.apple.com\/aperture\/'>Aperture<\/a> and Adobe's <a\nhref='http:\/\/www.adobe.com\/products\/photoshoplightroom\/'>Photoshop\nLightroom<\/a>, the photographer can work with images in a very wide color\nspace, reducing to sRGB or the like only when required (such as when\ngenerating JPG copies for the web, or for printing, etc.).\n\n<\/p>\n\n<p><b>Continued on the Next Page<\/b><\/p>\n<p>\n<\/p><p>\n\nThe technical discussion deepens on the next page: <a href='\/blog\/photo-tech\/color-spaces-page5\/'>Page 5: Chromaticity Diagrams<\/a>.\n\n<\/p><p>\n\nHowever, if you'd like to skip further technical stuff, feel free to skip directly to\n<a href='\/blog\/photo-tech\/color-spaces-page7\/'>Page 7: Recommendations and Links<\/a>.\n\n<\/p>\n\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"<p>So far in this article, we've talked about how color spaces are used to represent colors as numbers within an image file. But once a color-managed application has used the color space to convert the images colors into a device-independent understanding of color, how does the application convert that to the device-dependent information needed by your monitor or printer?<\/p> <p>The answer lies with the other half of color management: <b>device color profiles<\/b>... <\/p> <p><b>Color Profiles for Monitors, Printers, Paper, Scanners,... ?<\/b><\/p> <p>The first page of this article discusses color profiles for digital images, but there are also color profiles for [...]","protected":false},"author":1,"featured_media":0,"parent":251,"menu_order":4,"comment_status":"open","ping_status":"open","template":"","meta":{"footnotes":""},"_links":{"self":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/pages\/255"}],"collection":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/types\/page"}],"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=255"}],"version-history":[{"count":0,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/pages\/255\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/pages\/251"}],"wp:attachment":[{"href":"https:\/\/regex.info\/blog\/wp-json\/wp\/v2\/media?parent=255"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}