What Is Delta E? dE Values and Monitors Explained

Delta E, also called ΔE, is a set of standards established by the CIE (International Commission on Illumination) to measure the difference between colors. Despite its importance in color management, many people are unaware of what it is or how it’s calculated. This post aims to fill this gap and explain the basics behind Delta E.

Delta E (ΔE) is a measure of how different two colors are. The lower the value, the less difference there is between the two colors. A Delta E of 1 or less means that there’s practically no difference between them; they can be considered the same color for all intents and purposes (although professionals often use closer to a Delta E of 0.3).

The CIE established the ΔE standard in 1976, defining it as “the Euclidean distance in CIE Lab color space between the Munsell color of the test stimulus and that of the comparison stimulus .” This means that a pair of colors have a lower ΔE value if they’re closer together in color space, and a higher ΔE value if they’re further apart.

The CIE Lab color space is similar to the familiar RGB (Red-Green-Blue) color model used by computer monitors, but it uses different coordinates – lightness (L), red-green (a), and blue-yellow (b). For more information on how this color model is calculated and the differences between it and RGB, you can refer to my previous post here .

Delta E for Monitor Displays

What does all of that mean in practice? For our purposes, ΔE measures how similar two colors on a monitor display look when placed side-by-side. A higher Delta E means that the two colors will appear more dissimilar.

Delta E is often used when buying a new monitor. Manufacturers advertise ΔE figures for their displays, and these help you choose a screen with accurate color reproduction. For example, NEC’s multisync PA241W has a Delta E of 1.6 at its full native resolution of 1920×1200 pixels.

Many photographers use their monitors at 100% brightness and color temperature, which can lead to inaccuracies when viewing images that are supposed to be neutral in color. The precise value you should aim for depends on your personal preferences (and also the ambient lighting conditions), but sensible starting points would be Delta E no greater than 3 or 5 for reflective, and 5 or 7 for non-reflective work.

How This Relates to Camera Color Management Cameras can’t capture reality as it is due to the limits of perception of both our eyes and the camera sensor. This means that expectations need to be managed when processing raw files so that they will look reasonably close to what we saw through the viewfinder or what we see on a calibrated computer display. The camera’s color management is responsible for this and it does so by modifying its internal parameters to produce a file that has as accurate colors as possible.

One of the most important color reproduction processes is white balancing, which involves setting the “white point” in order to neutralize the image. By default, most cameras are set to record colors so that neutral grey is represented by the RGB values (128, 128, 128), which corresponds to a color temperature of approximately 5000K.

One of the parameters in white balancing is balance_magenta_blue, which sets the ΔE for the Magenta-Blue axis. This means that if we record a scene with this setting and then view it on a calibrated display, the colors should appear neutral. Unfortunately, this is not always the case as there can still be differences in color appearance due to things like illumination (e.g. side-lighting), viewing angles, and camera vignetting (unfortunately Live View can’t be used to assess this, so we would need to use a reference image captured with the camera’s optical viewfinder).

The image above shows an uncorrected white balance as set by the Canon EOS 60D. Yellow, green and blue tones are visible – there’s also noticeable vignetting on the top-right edge of the frame.

In the following image, I’ve taken a photo of my calibrated test target using the same camera settings as above but with a custom white balance correction applied in Lightroom 4 (I used the droplet method). You can see how neutral colors are now recorded – ΔE calculates to 3.43.

You might be thinking “So what? What does this have to do with my photography?”

The most obvious reason is if you are shooting products, real estate scenes, or other scenes where color accuracy is important. Even if your camera’s native white balance is slightly off, the overall colors in the scene will be more accurate when using a custom white calculated from a properly calibrated display.

Secondly, if you use a mix of cameras at your disposal (e.g. different bodies or lenses from different manufacturers), it’s possible that their white balances will produce slightly different colors despite being applied correctly. However I find this to be a minor issue as most cameras appear to have similar under-the-hood color processing nowadays. Thirdly, if you use multiple software tools to process your images (e.g. Capture One for tethering, Photoshop for editing), it’s important that the white balance is consistent between them in order to avoid color variations. Your colors should appear more uniform when using a calibrated display as the reference.

The reason why this is less of an issue nowadays is that we don’t necessarily need to use our cameras’ native profiles. Camera profiles can be calibrated either by using a custom white balance reference (e.g. the droplet method) or by taking an actual calibration target and photographing it (I know this is a strange concept but bear with me). By doing so, we can generate a custom profile that will compensate for any slight color variations between different cameras. For example, the Fujifilm X-T1 records blues slightly too cold out of the box despite using its “native” profile. I was able to fix this by applying a custom white balance calibration using my reference image (the process is very easy, all you need is a target and a calibration tool such as Adobe Camera RAW or Lightroom) and converting the resulting profile to Fujifilm’s X-trans RAF format. To my eye, the corrected colors are now more accurate (ΔE = 1.46 ).

If there is one thing that any photographer should get into the habit of doing, it’s calibrating your display. Even if you don’t print or edit your images on a calibrated monitor, it will help ensure that the colors in your images are as accurate as possible.