How to solve the problem of color change (chromatic aberration) after photos are uploaded to the Internet?

With the popularity of SLR cameras, everyone will take their beloved baby out to take photos and upload them to blogs, forums and various social networking sites to share with you. However, many people will find that sometimes the photos they take with SLR cameras will have different effects when they are opened on the local disk and displayed on the web page. The same picture, without any processing, has two completely different effects. Why is this happening?

Why do photos change color when they are sent online? First of all, the reason that people think of is that some websites will compress photos when users upload them in order to get faster browsing speed, so this will cause the loss of some information in the photos and make the photos appear certain distortion. However, with the popularity of broadband, most blogs, forums and other websites (especially professional photography websites) try their best to ensure that the photos uploaded by everyone are not compressed. But even so, many photographers will find that the color of the photos in the web page is different from the effect of the image processing software, so they can't blame the website. In fact, the culprit may be your browser.

Browsers are actually part of the color management system, but we seldom pay attention to their characteristics. Yes, although the browser itself seems to have nothing to do with the color effect of the display, it actually belongs to an important part of the color management system. In the last article, we have already introduced that the commonly used Windows system and Apple's Mac system have color management components, which match according to the ICC file information of cameras, monitors, printers, projectors and other external devices, while the browser, like image processing and viewing software, is also controlled by the color management system. Next, we will study what kind of photos, or under what conditions, we will see that the results on the local disk are different from those on the web page, and what are the reasons for the differences.

The display effect of the monitor is very important for the browser to support color management.

Speaking of color management system, we were in "just for literature and art?" Why do professional studios love apples? This paper introduces this in detail. Different devices have different color characteristics. For example, when taking a picture, the camera will record its complementary color ability as an ICC file embedded in the picture, and the color rendering ability of the display will also be recorded in the ICC file of the driver. The operating system reads ICC from the picture file, then converts the color information of the picture into the hair color of the display according to the ICC of the display, and finally corrects the original color of the display picture through gamma. The job of color management system is to match and unify the ICC of all hardware to achieve the best output effect.

Through ICC file, the color management system uniformly matches all devices. Every digital camera has its own ICC characteristics. After taking a picture, it will record its ICC information in each picture file for the color management system of the operating system to load and retrieve. For SLR cameras and some high-end DC, they have two color space attributes: sRGB and Adobe RGB. Usually, we use sRGB color space, but the color coverage of Adobe RGB is wider than sRGB, so users in high-end photography and publishing and printing industries will adopt Adobe RGB color space. When different color spaces are set, the ICC profile information written by the camera in the photo will be different.

SLR cameras always have color space options, and ICC file information is different in different color spaces. This is the problem: if you choose sRGB color space to take photos, because the Windows operating system uses sRGB color space by default, even programs that do not support loading ICC files (such as picture software or browsers) will be handed over to the Windows system for display and rendering, so that the color will hardly change; However, if you choose Adobe RGB color space to take photos, when you open a program that doesn't support ICC loading ability, there will be color cast (although most monitors don't support Adobe RGB color space, you can output good colors by re-converting ICC files through the color management system, but if you don't convert the color space at all, the actual difference will be great).

Shoot the same color card with Adobe RGB color space, upload it to the Internet and watch it with different browsers. Here, we do an experiment: adjust the camera to Adobe RGB color space, take a picture of the standard color card as shown above, upload it to the Internet, and open this picture with a browser that supports and does not support ICC file loading, otherwise the original ICC information of the photo will be unfortunately lost. There will be a difference as shown in the above figure: the color of the browser supporting ICC loading is relatively saturated, while the color of the latter is relatively dim, which is why many netizens think that the browser will have a color cast when looking at the picture. That is to say, if you use a browser that supports the ability to load ICC files (that is, has the ability of color management), you can basically avoid the problem of color cast under the condition that the ICC files of photos are preserved. So how do we check whether the browser we use supports the ability to load ICC files (that is, the ability to manage colors)?

Does my browser support color management?

Because Apple's Mac OS system adopts a powerful ColorSync color management system, as long as the hardware connected to it and the installed software are managed by ColorSync, no matter what graphics, videos, browsers and other software are used to open pictures in the Mac OS system, they are managed and constrained by ColorSync system and have the ability to load ICC files. So how do we judge whether our browser has this function under Windows system? (Windows color management system does not have the ability of unified management, and it is completely left to each software to decide. ) Here we provide a website that you can test yourself after entering:

This page contains two tests in total. You can click on the links "ICC Color Profile Test" and "Colors in IE9" to enter. Although the form is different, the test results are completely different. Let's take a look at the first test: after entering the page, the first picture consisting of four small pictures is the test result of your browser. The following is a description of the test results. This time we used five famous browsers: Microsoft IE, Google Chrome, Mozilla Firefox, Apple Safari and Opera. The browser programs we choose are all Windows versions.

The test results show that, from the test results, only when the colors of the four thumbnails are exactly the same, the support for color management ability is the best. Let's take a look at the performance of these five famous browsers.

The images displayed by browsers that do not support color management are very ugly.

Winner's report card From the results, all versions after Microsoft IE9, Apple Safari and Firefox 3. 6. 4 (parameters need to be modified) can well support the color management function, while all versions of Chrome and Opera and the old versions of IE and Firefox do not support the ability to load ICC files, that is, when viewing pictures with these browsers, there may be color cast. Let's look at another test result on the next page.

Test results and analysis of color management of professional display browser

A test may not explain much. Let's take the second test. In this test, if the browser can support the color management function well, it should display a complete picture instead of displaying different colors in the upper, middle and lower parts. We suggest clicking on the enlarged image to see the test results below.

Those who fail the above tests will still fail.

Excellent students can get good grades in any exam. In the second test, we can see that the new versions of IE, Firefox and Safari can support the color management function well, while Chrome and Opera are completely annihilated. It should be noted that IE9 browser brought us a surprise. What is surprising is not how excellent the performance is, but the lack of Microsoft's continuous improvement in color management. After all, its browser before the launch of IE8 didn't support the function of loading ICC files at all, but unfortunately, Microsoft didn't promote this new function when it released IE9, so many users didn't know it. Similarly, Firefox has also added support for color management in the newly released version (but the parameters need to be modified, and the setting method is introduced in the previous attachment).

What needs to be praised is that Apple Safari browser supports color management function from beginning to end, whether it is the Mac version or the Windows version. Apple naturally won't let this go in the official publicity, and its achievements in color management have won a good reputation from professionals. Although the version numbers of Chrome and Opera are very large, perhaps their design philosophy is to pursue speed and convenience, so they also give up functions such as color management. As for whether the browsers launched by Maxthon, sogou and other domestic manufacturers can support the color management function, interested readers can test for themselves.

As we have mentioned above, the ColorSync color management system in Apple's Mac OS is in charge of the color processing ability of each program, so even if you use the Chrome browser of Mac version, you can still pass the above two tests very easily.

In order to avoid the color cast when browsing photos on the Internet, it is best to save the picture file completely when shooting, and do not delete its original ICC file information, and then use a browser that supports the color management function (that is, supports the loading of ICC file information), or simply use the Apple Mac system, so as not to be afraid of "paranormal".

Attachment: How to set a browser that supports color management after Firefox 3.6.4 (Windows version only):

Go to gfx.color_management.enablev4 to set whether ICC v4 is supported, change it to true, and restart the Firefox browser.

Description: gfx.color_management.mode Here Firefox is defined by integers, and there are three modes that can be set:

1): the value of item is 0, which means that the color management function is turned off (that is, the ICC file for loading pictures is abandoned);

2): The item value is 1, which indicates that the color management function is turned on. The behavior is to call the ICC file when a picture containing the ICC file is detected. If the detected picture is not embedded in the ICC file, the ICC file currently set by the Windows operating system is used for conversion (the default color management file of Windows is SRGB ICC);

The value of item is 2, which means that only pictures with ICC files are subject to color management, while pictures without ICC files and other colors (including text) on web pages are not subject to color management. The display uses the ICC that Windows currently uses for conversion and output (the default color management file for Windows is sRGB ICC). At this time, if users use a wide color gamut display, they will feel that the color is somewhat exaggerated. After the setting is successful, you need to restart Firefox to take effect!