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Color Management Experiment Kit: If seeing is believing, how much does your monitor profile matter?

There are two approaches to learning anything: Learn theory and then try to apply it. Or (my preferred approach) start experimenting and worry about theory later.

This 'Color Management Experiment Kit' is for exploring the difference a monitor profile makes in what you see on your monitor screen. It has ICC monitor profiles to play with, experiments to try, and images to try them on. Think of it as the digital darkroom equivalent of being handed a kid's chemistry set, except the only thing you'll risk blowing up is a few pixels.

Written March 2013. Updated February 2015.

You decide: does your monitor profile matter?

Color management pundits can preach at you all day long about why you should use color management. But you aren't going listen until you have a darn good reason.

These experiments allow you to see for yourself how very small differences in monitor profiles produces very visible alterations in the colors displayed on your monitor screen. The downloadable "profiles pack" includes six synthetic monitor profiles, each of which deviates from sRGB by a very small amount, plus a couple of real monitor profiles.

Likely none of the profiles in the profiles pack are better than sRGB as a profile for your particular monitor, and most of them will be worse. If you can find a profile for your monitor on the internet, download it and add it to the test profiles for the experiments on this page. And of course if you normally use a custom monitor profile, add that profile to the list.

The following two websites offer profiles for a surprisingly large number of monitors and laptop screens. If your monitor isn't on either list, as always, search the internet:

The cold hard truth is that if you don't use color management, or if you do use color management but you use sRGB as your monitor profile, then you don't know what your images really look like. You only know what sRGB makes your images look like on your monitor. (Unless, of course, you've calibrated your monitor to exactly match sRGB — but another cold hard truth is that most LCD monitors can't be calibrated to exactly match sRGB.)

Note: These experiments assume that you have a standard monitor. If you have a wide-gamut monitor, the colors will be extremely oversaturated unless you use your monitor's sRGB preset. It should go without saying that the quality of an sRGB preset varies greatly from one make and model of monitor to the next. In other words, using an sRGB preset doesn't mean that you can safely use the sRGB profile as your monitor profile.

Setting up for the experiment

Here's how to do the experiments:

  1. Open a test image with a color-managed image editor.
  2. Make some changes to the Color Management settings.
  3. Watch what happens to the test image.

It really is that simple. It will longer to read through the experiments than do them. What may surprise you is how much you can learn about color management theory just by watching what happens to your images. Here's everything you need to do the experiments:

1. A color-managed image editor that allows you to easily change your monitor profile: GIMP allows you to easily change your monitor profile. Unfortunately, many image editors make changing your monitor profile difficult, requiring you to exit the program, change the system monitor profile, then restart the program.

This page assumes you are using Linux with GIMP 2.8.10 or later (you want a version of GIMP that uses LittleCMS version 2) or GIMP 2.9 from git. Probably GIMP on Windows or Mac will work just as well, but I'm running Linux so I don't know for sure.

2. Test images and profiles: Download and extract this Color Management Experiment Kit monitor profiles pack and test images. Put the test images in any convenient location. Put the ICC profiles wherever your editing program looks for ICC profiles. GIMP looks wherever you want it to look (good for GIMP, I wish all editing programs were this obliging). Most other image editing programs only search for ICC profiles in particular folders, but usually you can add a new folder.

3. A proper workspace environment: Because you want your eyes to accomodate to your monitor rather than to any surrounding light sources, dim your workspace lights so they are quite not as bright as your monitor. It's hard to judge colors on a monitor when your eyeballs are trying to ignore strong directional light, so keep extraneous light reflections off your monitor and out of your eyes. If you don't have specialized D50 lighting (I don't), window light works well as long as it's not reflecting off your screen (windows should be to the left or right of your field of view as you look at the monitor).

As you'll be judging color changes, there shouldn't be any strong colors in your field of view or on your desktop (my own desktop is a solid middle gray). Wear a dark gray or black shirt to avoid creating color reflections on your monitor. The experts recommend painting the walls a neutral gray, but spouses tend to object.

4. The GIMP Color Management settings dialog: If you've never opened the GIMP Color Management settings, now is a good time to get acquainted. Open GIMP. Open the GIMP Color Management settings by clicking "Edit/Preferences/Color Management". Then make the Color Management settings match the picture below:

GIMP 2.8 Color Management settings (GIMP 2.9 has a box for black point compensation, so if you are using GIMP 2.9, for this experiment uncheck the black point compensation box).
  1. Set Mode of operation to Color managed display.
  2. Set RGB profile to none.
  3. Set CMYK profile to none.
  4. Set Monitor profile to sRGB-IEC61966.icc (included in the color management kit profiles pack). Note: the GIMP profile boxes show the profile description, which is a bit of descriptive text embedded inside the profile; all the other profiles in the profiles pack have descriptions that exactly match their file names, but this profile has an extended description.
  5. Make sure "Try to use the system monitor profile" is unchecked.
  6. Set Display rendering intent to Relative Colorimetric.
  7. Set Softproof rendering intent to Relative Colorimetric.
  8. Make sure "Mark out of gamut colors" is unchecked.
  9. Set File Open behavior to Ask what to do, and for the experiments on this page, always click "Keep" when you open a test image.
  10. Click "OK" to close the Color Management dialog. Or leave it open if you prefer.

The experiment: Monitor profiles and displayed colors

1. Swimming pool pose. Photographer: Mark Evans; Source: Flickr; Licence: CC-BY.
2. River Man. Photographer: TheGiantVermin; Source: Flickr; Licence: CC-BY-SA.
3. Swan at Montreat. Photographer: Selena N. B. H.; Source: Flickr; Licence: CC-BY.

The purpose of this experiment is to let you decide for yourself whether the following claims are true:

  1. Small changes in your monitor profile make visible and even grossly obvious changes in the colors you see on your monitor screen.
  2. Your eyes quickly adapt to the new colors — after a few seconds or a minute, colors that looked unbelievably ugly start to look normal.

Step 1: Open GIMP if it's not already open. Make sure the Color Management settings are still set up as above. Then open the following test images from the "Color Management Experiment Kit":

  1. Swimming-pool-pose.jpg
  2. River-man.jpg
  3. Swan-at-Montreat.jpg

These three test images demonstrate that using the right monitor profile is especially important when judging the appeareance of highlights, bright, delicate colors; and neutral gray or white.

This experiment doesn't involve editing the test images, so you can minimize the Layers window and the Toolbox to free up some screen real estate. Also, under View you might want to uncheck showing the Rulers and Layer Boundary, and then Shrink Wrap the image so there are minimal distracting elements surrounding the image.

Step 2: Move the test images to one side of your screen and (re-)open the Color Management dialog ("Edit/Preferences/Color Management"). Position all the windows so you can make changes to the Color Management settings while observing what happens to the test images (this might take a little hand-eye coordination, but you'll get the hang of it very quickly).

Why is it important to look at the image while changing the monitor profile? From your brain's point of view, changing the monitor profile is very much like changing the color of the light falling on the original scene, which means your eyes will quickly accomodate to the new "lighting". In fact, your eyes accomodate so quickly that you'll want to change back and forth between sRGB and the alternative monitor profiles several times, always keeping an eye on the image as you change the monitor profile, and focusing not just on different test images, but sometimes on specific colors in each test image.

Experiment setup for GIMP.

Step 3: Watch what happens as you try different monitor profiles. Note: changing your monitor profile does not alter the actual image RGB values; it only alters the way those values are displayed on your monitor screen.

A neat thing about GIMP is that once you've selected a new monitor profile for the first time, GIMP remembers it, which makes it very easy to flick through from one monitor profile to another. When using GIMP, the experiment goes quickly because you don't have to click "OK" to see the resulting changes in the image colors. Just keep the Color Management settings dialog open and keep switching from one profile to the next as you examine the test images. (Caution: make sure you only have one instance of GIMP open and running, because changing the monitor profile in one open instance of GIMP doesn't change it in the others.)

The "Color Management Experiment Kit" includes the following monitor profiles:

  1. sRGB-IEC61966.icc — the original 1996 sRGB profile.
  2. sRGB-derived synthetic monitor profiles — each profile simulates one of the ways real monitor profiles can and do differ from sRGB:
    1. srgb-less-intense-red.icc
    2. srgb-more-intense-red.icc
    3. srgb-less-intense-green.icc
    4. srgb-more-intense-green.icc
    5. srgb-less-intense-blue.icc
    6. srgb-more-intense-blue.icc
  3. Real monitor profiles:
    1. NEC-2190uxi-monitor.icc — custom-built profile for a good quality LCD monitor.
    2. low-end-laptop.icc — custom-built profile for a low-end laptop screen.
    3. If your internet search turned up a profile for your monitor, add it to the list.
    4. Add your own custom monitor profile to the list, if you normally use one.

Click "Edit/Preferences/Color Management" and confirm that the currently selected monitor profile is "sRGB IE61966-2.1 (Equivalent to www.srgb.com 1998 HP profile)". Leave the Preferences dialog open (don't click "OK") and look at the three test images. Now select "srgb-less-intense-red.icc" as the new monitor profile (again, leave the Preferences dialog open) and watch what happens to the test images. Then do the same with "srgb-more-intense-red.icc". Then continue through the remaining synthetic and real monitor profiles.

As you change monitor profiles, watch the baby's skin tones and the pool water behind the baby. Also watch the sky and water reflections behind the canoist and the water surrounding the swan. You might want to alternate back and forth between the standard sRGB profile and the "srgb-less-intense-red.icc" and "srgb-more-intense-red.icc" profiles several times, each time watching a different test image.

Sometimes the changes are subtle, so it helps to go back to "sRGB-IEC61966.icc" before switching from one sRGB-derived monitor profile to the next. You can see the colors change, and at first they look odd, or at least different. If you stare for a while, do the new colors start to look normal?

If there is any doubt in your mind as to the actual colors in these test images, check with the GIMP eye-dropper:

4. Colorchecker brush strokes.
5. Paint chips.
6. Painted wood balloon.

Step 4: Close the test images that are already open, open the next three test images, and repeat the first three steps. The first three images were chosen to emphasize highlights and bright, delicate colors. These three images emphasize mid-range tonality and more saturated colors:

  1. Colorchecker-brush-strokes.png
  2. Paint-chips.jpg
  3. Painted-wood-balloon.jpg

The "Colorchecker brush strokes" and "Paint chips" colors are moderately to very saturated. The colors in the "Painted wood balloon" image are very close to the Colorchecker colors, but now the colors have a context. Real "sunny day blue sky" colors are usually very slightly on the cyan (rather than magenta) side of blue; the blue sky in this picture is a reasonably believable "sky blue" shading to more pronounced cyan at the horizon. Your experience may vary, but to me some of the test monitor profiles make the sky in the Painted wood balloon picture almost painful to look at (at least until my eyes have adjusted).

Because your eyes adjust so quickly to changes in how colors are displayed on your monitor screen, it's especially important with the "Colorchecker brush strokes" and "Paint chips" image that you look at the image while changing the monitor profile. You might even want to flick your way through the monitor profiles while focusing on only one color at a time.

The image below shows screenshots for Steps 3 and 4:

Four test images, displayed using three different monitor profiles.

If you are trying to color-balance the swan image so the swan looks white and the water looks neutral grey, can you trust what you see on your monitor screen? And what about the white plastic behind the paint chips — does this picture need color-balancing? or is your monitor profile misleading you? (Eye-droppering reveals that the plastic and the swan are already white and the water is already gray — neither image needs color-balancing.)

How much do the profiles in the profile pack differ from sRGB?

Chromaticity diagrams for the profiles in the profile pack

The sRGB ICC profile ("sRGB-IEC61966.icc" in the profile pack): The sRGB red, green, and blue primaries describe the display characteristics of consumer-grade CRT monitors manufactured in the 1990s. When you use sRGB as your monitor profile, your image editing program assumes that sRGB accurately describes how your monitor displays colors. So if your monitor isn't calibrated to match sRGB, then your monitor isn't showing you the right colors.

"CIE 1931 xy chromaticity diagram showing the sRGB gamut and the D65 white point". Licence: CC-BY-SA. Source: Wikimedia Commons.

Circles inside the horseshoe: The picture above is a representation of the sRGB color space profile. The brightly-colored horseshoe shape is a kind of footprint of all the colors that the average human can see. The red, green, and blue sRGB chromaticities (aka "primaries" and also ICC profile "colorants") are shown by the three small white circles with black dots in the middle. The primaries are connected by three lines which form a triangle. That larger circle in the middle of the triangle is the sRGB white point, but we won't be paying much attention to it.

Color gamut: The sRGB color space holds — and a true sRGB monitor can display — all the colors (actually chromaticities, but "colors" is close enough for our current purposes) that are inside the triangle determined by the three sRGB primaries. But it doesn't hold — and a true sRGB monitor can't display — any of the colors that are outside the triangle. To hold more colors, the primaries would need to be farther apart. (Lest there be any confusion, the footprint shown above is a graphical representation — it doesn't actually show you any of the real world colors that fall outside the sRGB triangle.)

The sRGB-derived synthetic monitor profiles in the profile pack: I created the sRGB-derived synthetic monitor profiles by slightly modifying one sRGB primary per profile. In the following image, the location of each synthetic profile's modified primary is shown by the larger black circle with the white spot in the middle:

In the image above:

  • The three synthetic monitor profiles in the top row are identical to sRGB, except one primary is slightly less intense than the corresponding sRGB primary. In other words, the new primary is inside the sRGB triangle. Low-end LCD displays, and especially low-end laptop displays, usually have one or more primaries that are less intense (sometimes much less intense) than the corresponding sRGB primaries.
  • The three synthetic monitor profiles in the bottom row are identical to sRGB, except one primary is slightly more intense than the corresponding sRGB primary. In other words, the new primary is outside the sRGB triangle. Reasonably good and high-end LCD displays have primaries that are more intense than sRGB. Wide-gamut LCD displays have a green primary that is much more intense than the corresponding sRGB green primary.

sRGB compared to the NEC monitor profile and the low-end laptop monitor profile:

Above on the left, the NEC profile primaries are more intense and also different colors than the corresponding sRGB primaries. Above on the right, the low-end laptop profile primaries are less intense and also different colors than the corresponding sRGB primaries.

All chromaticity diagrams on this page are derived from and subject to the same licence as "CIE 1931 xy chromaticity diagram showing the sRGB gamut and the D65 white point". Licence: CC-BY-SA. Source: Wikimedia Commons.

Extra credit:

Comparing pairs of sRGB-derived synthetic monitor profiles:

Which "modified red" profile makes the highlights look more red than the real sRGB? Which one makes the highlights look less red (which is to say more cyan, cyan being the opposite of red) than the real sRGB?

Repeat with the remaining pairs of sRGB-derived synthetic monitor profiles: "srgb-less-intense-green.icc" and "srgb-more-intense-green.icc", and with srgb-less-intense-blue.icc and srgb-more-intense-blue.icc. For reference purposes, the opposite of green is magenta and the opposite of blue is yellow.

Try to relate your observations to the chromaticities diagrams shown above. When the synthetic profile's primary is more/less intense than the corresponding sRGB primary, which way do the colors shift?

Monitor profiles and saturation:

Between the NEC monitor profile and the low-end laptop monitor profile, which profile makes the images look the most saturated? Which one makes the images look the least saturated? Can you relate your observations to the chromaticities diagrams shown above?

What happens when you keep the monitor profile constant and change the image profile?

Change your monitor profile back to the real sRGB ("sRGB-IEC61966.icc"). Select "Swan-at-Montreat.jpg" and go to "Image/Mode". See where it says "Assign Color Profile" and "Convert to Color Profile"? Select "Assign Color Profile" and one at a time, assign the various sRGB-derived synthetic monitor profiles. Compare results with the previous "Extra Credit".

Then try the NEC monitor profile, the low-end laptop profile and any other real monitor profile you might have.

Try to relate your observations to the chromaticities diagrams shown above.

What happens when the image profile matches the monitor profile?

Background: sRGB isn't just a monitor profile. It's also the color space for most images that are displayed on the web or that come from a point-and-shoot camera. All the test images in the "color management experiment kit" are actually in the sRGB color space and also have the sRGB profile embedded in their metadata. So when you use "sRGB-IEC61966.icc" as your monitor profile, then the test images have the same profile as your monitor. So the question is, when the image that you are viewing on your monitor has exactly the same profile as you've assigned to the monitor itself, what happens?

Procedure: Pick one of the test images, go to "Preferences" and select "srgb-less-intense-red.icc" as the monitor profile. Then assign "srgb-less-intense-red.icc" to the image itself. What happens? Now go to "Preferences" and select "srgb-more-intense-red.icc" as the monitor profile, and then assign "srgb-more-intense-red.icc" to the image itself. What happens? Repeat with additional synthetic and/or real monitor profiles, until you are sure you know what's happening, and then re-assign the real sRGB profile to the image and in Preferences set the monitor profile back to the real sRGB profile ("sRGB-IEC61966.icc").

Conclusion

The premise behind these experiments is that without calibrating and profiling your monitor, you don't know what your images really look like. The experiments were designed to show how very small differences in monitor profiles produces very visible alterations in the colors displayed on your monitor screen.

So if seeing is believing, does your monitor profile matter? Are you sure that sRGB is a "good enough" profile for your monitor?

You might have noticed there are several more monitor profiles in the profile pack that weren't used in these experiments. I'm working on writing up a couple of quick experiments that allow you to see the effect of your monitor profile on the shadow tones of your images. Your images might have a lot more (or less) deep shadows than you realize, if your monitor profile doesn't accurately describe your monitor.