In a world full of large color gamut devices, what is sRGB good for today?
There was a time when an "all sRGB" workflow meant you didn't have to worry about color management. It also meant that when editing your sRGB images, all your image colors were accurately displayed on your calibrated-to-sRGB CRT monitor. With the advent of the LCD monitor, many advantages of the old "all sRGB" workflow no longer apply. So what is sRGB good for today?
Written August 2013. Minor update in February 2015.
CRTs and the "all sRGB" workflow
1996: Birth of the "all sRGB" workflow
Back in 1996, Hewlett-Packard and Microsoft proposed the sRGB color space as a standard for consumer-level imaging:
Hewlett-Packard and Microsoft propose the addition of support for a standard color space, sRGB, within the Microsoft operating systems, HP products, the Internet, and all other interested vendors. . . . Based on a calibrated colorimetric RGB color space well suited to Cathode Ray Tube (CRT) monitors, television, scanners, digital cameras, and printing systems, such a space can be supported with minimum cost to software and hardware vendors [emphasis added] (A Standard Default Color Space for the Internet - sRGB).
The manufacturers of consumer-level imaging devices and all the people responsible for creating standards for things like operating systems and the World Wide Web all thought the Hewlett-Packard/Microsoft proposal was a great idea. Pretty soon consumers found themselves in an "all sRGB" world:
- sRGB was adopted as the officially assumed ICC profile for the World Wide Web and for the Microsoft and Linux operating systems.
- CRT monitors were sold, that could be calibrated to sRGB. And "no color management" digital imaging software was developed, that assumed that the monitor was calibrated to sRGB and all digital images were sRGB images.
- Scanners were sold, that only produced scans of prints, film, and transparencies that were already converted to the sRGB color space. Digital cameras were sold, that only produced in-camera jpegs that were already converted to the sRGB color space. And printers were sold, that only accepted sRGB images as input for printing.
Benefits of the "all sRGB" workflow
No color management required:
The benefits of an "all sRGB" workflow were obvious. Because everything was done in the sRGB color space, you didn't have to worry about color management. If you did happen to use color-managed software, you could set everything, including your monitor profile, to sRGB and then completely forget about color management.
What you see is what you got, IF . . .
Best of all, Hewlett-Packard and Microsoft intentionally designed sRGB to match the display characteristics of consumer-grade CRT monitors. So if you calibrated your CRT monitor to match sRGB, it really did match sRGB and you really could "see all the colors" while you were editing your sRGB images.
Note the "if" in the above paragraph because it carried a sting: The "all sRGB" workflow presumed that you, the consumer, bought and used the necessary equipment to calibrate your CRT to match sRGB. Most consumer CRT monitors were set up from the factory to be far too bright and blue to match sRGB, and even those that were factory-calibrated to match sRGB pretty quickly drifted out of calibration. Unfortunately, not all CRTs could be calibrated to match sRGB. The cheaper consumer-grade CRTs couldn't be calibrated at all, not having the necessary access controls. Of the CRTs that did provide calibration controls, some only allowed for very basic twiddling rather than the full access required for a proper calibration.
Even more unfortunately, most of us consumers really had no idea we were using uncalibrated CRTs and so when we viewed our sRGB images on our CRT monitors, the chance that we actually were viewing accurate colors was essentially nil. Speaking from my own experience, I had been cheerfully editing sRGB images on my uncalibrated CRT for a couple of years before I accidentally discovered that "something" was not right when an image I had carefully color-corrected to have nice colors on my own supposedly high quality CRT (which showed colors as far more blue than they actually were), looked really awful on my husband's supposedly identical high quality CRT (which showed colors as far more yellow than they actually were).
sRGB, the Universal (device and working space) Profile?
If you are reading this page, then you probably know at least a little bit about ICC profiles and color management. So you already know that sRGB itself is an RGB working space ICC profile. Hopefully you also know that there are other RGB working space ICC profiles (AdobeRGB1998, AppleRGB, BetaRGB, and so forth). In your digital darkroom, you've probably used sRGB as your working space profile. You might also be using sRGB as your monitor profile (although you really shouldn't use sRGB as a profile for your LCD monitor). You might have an sRGB scanner or printer. And you might have your digital camera set up to produce in-camera sRGB jpegs.
What you might not have realized or ever thought about is how very odd it is that sRGB serves as a sort of "universal" ICC profile, capable of simultaneously acting as a working space profile and also as the device profile for devices as different as a monitor, a printer, a scanner, and a camera. A brief clarification of the differences between device and working space profiles might be helpful:
The differences between a device ICC profile and a working space ICC profile
ICC color space profiles describe different color gamuts. An ICC color space profile's color gamut refers to the volume, size, and shape occupied by that color space profile in the CIELAB reference color space.
A working space ICC profile is an abstract mathematical construct designed to be convenient for image editing. There are many different RGB working space profiles, but most of them are simple matrix profiles, so their shapes and position in CIELAB space end up being variations on the same theme.
A device ICC profile describes the color gamut of a real-world device like a scanner, monitor or printer/ink/paper combination. Compared to working space profiles, device profiles are messy, mathematically complicated, and quite diverse, depending as they do on the device's underlying technologies and materials.
How can sRGB be many different device profiles and also a working space profile, all at the same time?
If device profiles are complicated and diverse, depending as they do on the device's underlying technologies and materials, and if working space profiles are mathematical constructs designed to be convenient for image editing, how can sRGB simultaneously function as a device profile for printers, monitors, scanners, and cameras, and also function as a working space profile?
The answer is straightforward: the only way that sRGB can function as all these device profiles is if the devices in question has been calibrated by the consumer and/or has been designed by the manufacturer to match the sRGB color space. As device color gamuts can't be made arbitrarily larger, "matching sRGB" means shrinking the theoretically available device color gamut down to as close a match as possible to the sRGB color gamut.
CRTs vs printers vs scanners and digital cameras
A CRT monitor could be calibrated to exactly match sRGB:
CRT monitors were a special case. Because the sRGB ICC working space profile was designed to match the display characteristics of CRT monitors, a properly designed CRT monitor really could be calibrated to exactly match sRGB. Which means that in the special case of a calibrated-to-sRGB CRT monitor, if you then profiled your calibrated CRT monitor, the color gamut described by the monitor profile would in fact be exactly equal to the sRGB color gamut (see also Why not all the colors? Why is sRGB so small?).
Apart from the special case of CRT monitors, for all the other sRGB devices, what "calibrated to match sRGB" and "designed to match sRGB" meant (and means) in practice is the following: Whatever messy or irregular color gamut the device has in reality, has been artificially made sufficiently smaller such that the device only produces (for input devices like scanners and digital cameras) or only accepts (for output devices like printers) images that are already in the sRGB color space. All other colors that the device might be otherwise be capable of producing/accepting are clipped or otherwise modified to fit within the sRGB color gamut.
No printer can print all possible sRGB colors, but most printers can print some colors that exceed the sRGB color gamut:
An sRGB printer is in a kind of double-bind. On the one hand, an sRGB printer can't actually print all the sRGB colors because there are certain colors (especially saturated blues and reds) that are within the sRGB color gamut, that ink-and-paper simply can't reproduce. So in reality sRGB printers can only print a subset of all sRGB colors. And on the other hand, ink-and-paper can easily produce greens, yellows, and cyans that exceed the sRGB color gamut (depending on the ink, the paper, and the printer, of course), if the printer hasn't been arbitrarily restricted to printing only sRGB colors.
Printers make colors by combining different colors of ink on paper. CRT monitors made color by combining different colors of light emitted by phosphors. Given the differences between printer and monitor technologies, it's not too surprising that the CRT-derived sRGB color space isn't a very good fit for printers, not even for printers advertised as "sRGB printers": you always get a smaller color gamut than the printer could otherwise accomodate if it weren't restricted to sRGB colors.
Digital cameras and scanners can capture all possible sRGB colors, plus a whole lot of colors that exceed the sRGB color gamut:
When you set your digital camera to output an sRGB image, all the RGB values that your camera's internal computer-interpolated from the sensor's raw data, that correspond to colors that fall outside the sRGB color gamut, are clipped or otherwise modified to fit within the sRGB color gamut before the image is saved to your camera's storage card.
The good news is that unlike printers, prosumer and professional-grade digital cameras and scanners actually can capture all possible sRGB colors. The bad news, of course, is that if you only use your digital camera to output sRGB jpegs, or if you are using an "sRGB only" scanner, then your input device is potentially throwing away a lot of colors that would otherwise could have been retained in a fully color-managed, non-sRGB workflow.
Some people wanted larger color gamuts
It didn't take too long before device manufacturers realized that a significant percentage of the growing number of "prosumer" and professional photographers wanted input and output devices with larger color gamuts. And if it meant they could use the full potential color gamuts of their various input and output devices, these gamut-hungry prosumers and professionals were quite prepared to deal with color management, right down to the nitty-gritty of calibrating and profiling their own devices.
So printers, scanners, and cameras with larger-than-sRGB color gamuts commanded higher price tags and became a point of competition between manufacturers. Fifteen years ago on the input side, film and slides were already capable of producing colors that exceeded the sRGB color gamut, so there was a demand for scanners with larger color gamuts, that could be profiled by the consumer instead of artificially "calibrated down" by the manufacturer to match sRGB. And on the output side, existing printer technology already exceeded the sRGB color space in the all-important saturated greens and yellows. Hence the proliferation of larger and larger RGB working spaces such as AdobeRGB1998, BestRGB, BetaRGB, and DonRGB: all of these color spaces were an attempt to find "just the right size" color space to accomodate the entire range of colors that scanners could capture and printers could print.
Today on the input device side, film and slides make up a much smaller portion of the prosumer/professional market today than was the case fifteen years ago. But prosumer and professional digital cameras, when shooting raw and profiled, can produce colors that far exceed the sRGB color gamut. On the output device side, today's wide-gamut LCD monitors can display colors that fall outside the sRGB color gamut, and cutting edge printer technology continues to push existing print color gamut boundaries.
Some people wanted an "all sRGB" workflow
Not everybody, not even all professional photographers, needed or wanted to take advantage of larger-than-sRGB color gamuts. For these people the start-to-finish "all sRGB" workflow had the advantages of speed, simplicity, and convenience. Because sRGB was simultaneously the input color space, the working space and the output color space, there was no need to worry about softproofing or color management. And perhaps most importantly, editing an sRGB image on a CRT monitor that had been calibrated to match the sRGB color space meant that "what you see is what you got": all the colors in your sRGB image could be accurately viewed on your properly calibrated CRT monitor.
The LCD monitor and the end of the "all sRGB" workflow
Whatever the case might have been in 1998, for most of us the "all sRGB, no color management needed, what you see is what you get" workflow doesn't work any more. You can still purchase sRGB-only printers and scanners, you can still output sRGB images from your digital camera, and of course you can still use sRGB as a working space. But the cornerstone of the "all sRGB" workflow was the fact that the CRT monitor could be calibrated to exactly match sRGB, and for most of us that cornerstone disappeared right along with the old CRTs.
What has changed since the advent of LCD monitors?
A decent quality CRT monitors could be calibrated to exactly match sRGB. But because of the different technologies used to make colors, the vast majority of today's LCD monitors can't be calibrated to match sRGB. So if you care even a tiny little bit about seeing colors accurately displayed on your monitor screen, you really shouldn't be using sRGB as your LCD monitor's profile:
- If you insist upon using sRGB as your LCD monitor's profile, the colors you see will be systematically wrong, to the extent that your monitor's actual color gamut differs from the sRGB color gamut.
- If you edit your images in a non-color-managed image editor, the colors you see will still be wrong because non-color-managed image editors assume you are using a monitor calibrated to match sRGB.
On a properly calibrated CRT, if you viewed an sRGB image on the World Wide Web, the image colors are were displayed correctly, regardless of whether your browser was color managed or not. Today, in order to see (depending on your LCD monitor, most but not all) colors in an sRGB image displayed correctly on your monitor screen, you need a properly color-managed browser and also an accurate profile for your LCD monitor.
Finally, even if you use a color-managed workflow and have an accurate profile for your LCD monitor, if you continue to use sRGB as your working space profile because you want to "see all the colors" while editing your images, you are probably deluding yourself: Today's low-end LCD monitors can't even come close to reproducing all sRGB colors. The better LCD monitors can display colors that fall completely outside the sRGB color gamut, but many of them still can't reproduce all sRGB colors, being weak in the most saturated sRGB blues. Only the more expensive "widest of the wide gamut" monitors can show all sRGB colors. No doubt monitor technology will continue to improve and more and more of us will enjoy the benefits of larger and larger display color gamuts. But as of 2014, simply assuming you can see all the sRGB colors on your LCD monitor is not a good idea.
Given the changes in monitor, printer, camera and other device technologies and the ready availability of high bit depth color-managed image editors, what's sRGB good for today?
The "all sRGB" workflow today — still useful if . . .
The two major advantages of the "all sRGB" workflow — being able to see all sRGB colors on your calibrated CRT monitor and not having to worry about color management — are long gone unless you have a high end monitor that really can be calibrated to sRGB. So for the rest of us, what's left of the "all sRGB" workflow in the year 2014? If . . .
- You only use your digital camera or scanner to output in-camera-produced sRGB images, or else shoot raw and immediately convert to sRGB for output
- You only output sRGB images for the web, or use either a consumer-level sRGB printer or a printing service that only accepts sRGB images
- You understand that you need to use color management and an accurate monitor profile
- You also understand using sRGB as your working space no longer means "what you see is what you get", unless you have a high end wide gamut monitor . . .
. . . then sRGB is still "just the right size" as a working space for editing your sRGB images. However, the only remaining advantage of using sRGB in this special use case is that you don't need to worry about soft proofing before outputting your final image to sRGB, because your working space and output space are the same (but you do need to worry about soft proofing to your monitor screen while you are editing, unless you've calibrated it to match sRGB as closely as possible).
The other reason for using sRGB as your working space is, of course, if you are using an 8-bit image editor. Larger working spaces too easily result in posterization when used for 8-bit image editing. However, given today's fast computers, cheap RAM, and the steady increase in the number of truly excellent 16-bit integer and 32-bit floating point color-managed RGB image editors, the limitations of 8-bit image editing are soon to be relegated to the dustbins of digital image editing history. (As an aside and in case you are new to open source imaging, some of the more well-known open source general and special purpuse high bit depth image editors are Cinepaint — still useful, albeit seemingly no longer in active development and not easy to install from source, deLaboratory, DigiKam/ShowFoto, Enblend/Enfuse, Hugin, ImageMagick, and Krita, with Gimp soon to follow. The raw processors Darktable, Photivo, and RawTherapee are all also capable image editors in their own right and can open and edit 16-bit pngs and tiffs; Darktable also can output, open and edit 32-bit floating point OpenEXR and floating point tiff images.)
For images posted to the web, sRGB is still the preferred output ICC profile
sRGB is still the standard and preferred output ICC profile for images displayed on the World Wide Web. One might be tempted to suggest that perhaps a new standard could be created that reflects the display characteristics of LCD monitors. But LCD monitor technologies vary so much from one make and model to the next that there is no such thing as lowest common denominator "universal LCD" monitor profile. So sRGB remains the best profile for publishing images to the web.
If your image editing goal is to produce web content, then unless you have a really good reason to the contrary, sRGB should be your output color space. If sRGB is your intended output color space, then also using sRGB as your working space has the obvious advantage that you don't have to worry about softproofing your final image. But it also has the disadvantage that unless you are using one of the widest of the wide gamut LCD monitors, and depending of course on your image's color gamut, some of your image colors might not be accurately displayed on your monitor screen.
Conclusion: sRGB is still useful today, but not as useful as it was ten or fifteen years ago
For reasons deeply rooted in the history of digital imaging and sanctified by standards, sRGB still has a special place in the long list of standard RGB working spaces:
- In this day and age of improperly color-managed or non-color-managed browsers, sRGB is still the safest color space for images posted to the web.
- The all-sRGB workflow still has benefits if your goal is to output sRGB images for the web or for an sRGB printer. (As an aside, if your goal is to print sRGB images on an sRGB printer, you might find the new color.org sRGB print workflow of interest. But be forewarned: the supplied color.org sRGB profiles are not open source and are not the same as the sRGB profile created by Hewlett-Packard and Microsoft back in 1996.)
Just make sure you use sRGB appropriately, keeping in mind the limitations of editing sRGB images on an LCD monitor. Also consider your own image editing goals because the old tradeoff between convenience and a larger color gamut still remains. For many years now printers can print colors and cameras can output colors that exceed the sRGB color gamut. So for you, in your digital darkroom, is the extra effort to recover and use the larger color gamut worth the (artistic or monetary) payoff?
What about the future? On the one hand, monitor technology continues to improve and so someday the all-sRGB workflow might again mean that "what you see is what you get" while editing sRGB images in your digital darkroom. On the other hand, color-managed browsers hopefully also will improve to the point where it's acceptable to use ICC profiles other than sRGB for images posted to the web. However, I suspect that sRGB will be around for a long time to come as the "least common denominator" output profile for images posted to the web for audiences who don't understand and don't use color management.