Quote of the day: "I swear, by my life and my love of it, that I will never live for the sake of another man, nor ask another man to live for mine." --Ayn Rand, Atlas Shrugged
While it is easy to display images on the Internet, it can be difficult to view them exactly as the photographer intended. There are many issues involved in displaying images on a computer including color spaces and color calibration. A color space is way of mapping the discrete color values which comprise image pixels onto the infinite number of possible colors. Color calibration is a method of tuning an output device to increase the accuracy of the color representation.
The most common color spaces are sRGB and Adobe RGB. Adobe RGB has a slightly larger color gamut than sRGB, while sRGB has more precision in representing the colors it can encode. sRGB is normally used for images on the Internet, while Adobe RGB is commonly used by photographers and graphic designers. A JPEG file can use either color space, and each red, green, and blue value is represented by an 8-bit number (0-255). Note that if a photographer uses Adobe RGB for image recording and processing, the image is normally converted to sRGB for display on the Internet. Theoretically this should not be necessary, but in practice it is the best option at the moment (see below).
All image output devices, such as monitors and printers, have restrictions on the colors they can display (they have their own color gamut). In addition, their accuracy can vary based on the quality of the hardware and the age of the device. A low cost monitor, for example, may have a smaller gamut than the image color space--if so, the monitor cannot display all the colors in the image, and some colors will be changed to displayable colors. Naturally, this affects the appearance of the image. Monitors designed for photographers and graphics professionals usually havve larger color gamuts, although there still may be a small number of image colors that are outside the gamut of the monitor (monitors with full coverage of the Adobe RGB gamut can cost well over $1,000.00).
However, even if the monitor has a large gamut the color accuracy can be low due to manufacturing tolerances and/or age. To ensure the color accuracy is high, photographers use color calibration products which can measure the actual output colors on the monitor screen for given inputs and then create an ICC profile which automatically corrects the input colors to compensate for any display inaccuracy. A similar technique is used for printers, so that the photographer can depend on a good correlation between monitor colors and print colors (at least the best possible correlation given that the display modalities are very different). Note that anyone viewing images online without a calibrated monitor may not be seeing the exact image that the photographer intended.
As mentioned above, the color space of an online image should not be an issue for displaying that image correctly if the browser and the computer operating system are capable of properly dealing with the image. If the image has an embedded ICC profile, then the browser should be able to use this information to adjust the colors for display on the monitor. However, some browsers ignore any embedded color space profile and treat the image in a default manner. For example, Microsoft's Internet Explorer browsers prior to version 9 treat all images as sRGB. If the image uses the Adobe RGB color space the colors are less saturated, especially in the red part of the color spectrum. Since the majority of people use a Microsoft Windows operating system and therefore are likely to use Internet Explorer as their browser, it has become a common practice to translate images to the sRGB color space for Internet display. This is the safest strategy, since any browser which does process image color spaces will use the embedded ICC profile to ensure the image is displayed properly (ideally).
Even though using the sRGB color space should be the solution, there are still some issues. I find that translating images to sRGB does increase color saturation and boosts red colors. While I try to not let this affect my image processing, I find that I am sometimes compensating for the translation effects when editing my images. This is not a good, since I print my images using the Adobe RGB color space, and I sometimes need to correct the printed image because the colors are not what I am seeing when I look at my Internet JPEG images on my monitor (I tend to be biased toward how images display in a browser because I do not print often).
I have recently started using the Adobe Safari browser, due to some problems with Internet Explorer. I instantly noticed that the images were not displaying properly--low saturation and loss of red intensity. This is exactly what happens when an Adobe RGB image is viewed in Internet Explorer. However, Safari is supposed to be capable of understanding embedded image ICC profiles, and should be able to properly display an sRGB image. The problem seems to be that Safari does a translation to the monitor color space which is affecting the image (or, more likely, Safari is doing the correct thing and Internet Explorer is doing something wrong). So even though the image is using the sRGB color space, there is something different about how Safari processes the image for diasplay and how Internet Explorer processes the image for display.
Needless to say, dealing with Internet image color can be quite confusing and frustrating. For the moment, I must keep using sRGB and depending on the Internet Explorer image display method, since I don't want to reprocess all the images on these web pages. The result is that the images may not display properly in other browsers, such as Safari. My apologies to anyone using a different browser--for the moment you may not be seeing the images as I intended them to be viewed...