gamma correction for lcd monitors factory

Problems like extremely poor display of shadow areas, blown-out highlights, or images prepared on Macs appearing too dark on Windows computers are often due to gamma characteristics. In this session, we"ll discuss gamma, which has a significant impact on color reproduction on LCD monitors. Understanding gamma is useful in both color management and product selection. Users who value picture quality are advised to check this information.

* Below is the translation from the Japanese of the ITmedia article "Is the Beauty of a Curve Decisive for Color Reproduction? Learning About LCD Monitor Gamma" published July 13, 2009. Copyright 2011 ITmedia Inc. All Rights Reserved.

The term gamma comes from the third letter of the Greek alphabet, written Γ in upper case and γ in lower case. The word gamma occurs often in everyday life, in terms like gamma rays, the star called Gamma Velorum, and gamma-GTP. In computer image processing, the term generally refers to the brightness of intermediate tones (gray).

Let"s discuss gamma in a little more detail. In a PC environment, the hardware used when working with color includes monitors, printers, and scanners. When using these devices connected to a PC, we input and output color information to and from each device. Since each device has its own unique color handling characteristics (or tendencies), color information cannot be output exactly as input. The color handling characteristics that arise in input and output are known as gamma characteristics.

While certain monitors are also compatible with color handling at 10 bits per RGB color (210 = 1024 tones), or 1024 x 3 (approximately 1,064,330,000 colors), operating system and application support for such monitors has lagged. Currently, some 16.77 million colors, with eight bits per RGB color, is the standard color environment for PC monitors.

When a PC and a monitor exchange color information, the ideal is a relationship in which the eight-bit color information per RGB color input from the PC to the monitor can be output accurately—that is, a 1:1 relationship for input:output. However, since gamma characteristics differ between PCs and monitors, color information is not transmitted according to a 1:1 input:output relationship.

How colors ultimately look depends on the relationship resulting from the gamma values (γ) that numerically represent the gamma characteristics of each hardware device. If the color information input is represented as x and output as y, the relationship applying the gamma value can be represented by the equation y = xγ.

Gamma characteristics are represented by the equation y = xγ. At the ideal gamma value of 1.0, y = x; but since each monitor has its own unique gamma characteristics (gamma values), y generally doesn"t equal x. The above graph depicts a curve adjusted to the standard Windows gamma value of 2.2. The standard gamma value for the Mac OS is 1.8.

Ordinarily, the nature of monitor gamma is such that intermediate tones tend to appear dark. Efforts seek to promote accurate exchange of color information by inputting data signals in which the intermediate tones have already been brightened to approach an input:output balance of 1:1. Balancing color information to match device gamma characteristics in this way is called gamma correction.

A simple gamma correction system. If we account for monitor gamma characteristics and input color information with gamma values adjusted accordingly (i.e., color information with intermediate tones brightened), color handling approaches the y = x ideal. Since gamma correction generally occurs automatically, users usually obtain correct color handling on a PC monitor without much effort. However, the precision of gamma correction varies from manufacturer to manufacturer and from product to product (see below for details).

In most cases, if a computer runs the Windows operating system, we can achieve close to ideal colors by using a monitor with a gamma value of 2.2. This is because Windows assumes a monitor with a gamma value of 2.2, the standard gamma value for Windows. Most LCD monitors are designed based on a gamma value of 2.2.

The standard monitor gamma value for the Mac OS is 1.8. The same concept applies as in Windows. We can obtain color reproduction approaching the ideal by connecting a Mac to a monitor configured with a gamma value of 1.8.

An example of the same image displayed at gamma values of 2.2 (photo at left) and 1.8 (photo at right). At a gamma value of 1.8, the overall image appears brighter. The LCD monitor used is EIZO"s 20-inch wide-screen EV2023W FlexScan model (ITmedia site).

To equalize color handling in mixed Windows and Mac environments, it"s a good idea to standardize the gamma values between the two operating systems. Changing the gamma value for the Mac OS is easy; but Windows provides no such standard feature. Since Windows users perform color adjustments through the graphics card driver or separate color-adjustment software, changing the gamma value can be an unexpectedly complex task. If the monitor used in a Windows environment offers a feature for adjusting gamma values, obtaining more accurate results will likely be easier.

If we know that a certain image was created in a Mac OS environment with a gamma value of 1.8, or if an image received from a Mac user appears unnaturally dark, changing the monitor gamma setting to 1.8 should show the image with the colors intended by the creator.

Eizo Nanao"s LCD monitors allow users to configure the gamma value from the OSD menu, making this procedure easy. In addition to the initially configured gamma value of 2.2., one can choose from multiple settings, including the Mac OS standard of 1.8.

To digress slightly, standard gamma values differ between Windows and Mac OS for reasons related to the design concepts and histories of the two operating systems. Windows adopted a gamma value corresponding to television (2.2), while the Mac OS adopted a gamma value corresponding to commercial printers (1.8). The Mac OS has a long history of association with commercial printing and desktop publishing applications, for which 1.8 remains the basic gamma value, even now. On the other hand, a gamma value of 2.2 is standard in the sRGB color space, the standard for the Internet and for digital content generally, and for Adobe RGB, the use of which has expanded for wide-gamut printing,.

Given the proliferating use of color spaces like sRGB and Adobe RGB, plans call for the latest Mac OS scheduled for release by Apple Computer in September 2009, Mac OS X 10.6 Snow Leopard, to switch from a default gamma value of 1.8 to 2.2. A gamma value of 2.2 is expected to become the future mainstream for Macs.

On the preceding page, we mentioned that the standard gamma value in a Windows environment is 2.2 and that many LCD monitors can be adjusted to a gamma value of 2.2. However, due to the individual tendencies of LCD monitors (or the LCD panels installed in them), it"s hard to graph a smooth gamma curve of 2.2.

Traditionally, LCD panels have featured S-shaped gamma curves, with ups and downs here and there and curves that diverge by RGB color. This phenomenon is particularly marked for dark and light tones, often appearing to the eye of the user as tone jumps, color deviations, and color breakdown.

The internal gamma correction feature incorporated into LCD monitors that emphasize picture quality allows such irregularity in the gamma curve to be corrected to approach the ideal of y = x γ. Device specs provide one especially useful figure to help us determine whether a monitor has an internal gamma correction feature: A monitor can be considered compatible with internal gamma correction if the figure for maximum number of colors is approximately 1,064,330,000 or 68 billion or if the specs indicate the look-up table (LUT) is 10- or 12-bit.

An internal gamma correction feature applies multi-gradation to colors and reallocates them. While the input from a PC to an LCD monitor is in the form of color information at eight bits per RGB color, within the LCD monitor, multi-gradation is applied to increase this to 10 bits (approximately 1,064,330,000 colors) or 12 bits (approximately 68 billion colors). The optimal color at eight bits per RGB color (approximately 16.77 million colors) is identified by referring to the LUT and displayed on screen. This corrects irregularity in the gamma curve and deviations in each RGB color, causing the output on screen to approach the ideal of y = x γ.

Let"s look at a little more information on the LUT. The LUT is a table containing the results of certain calculations performed in advance. The results for certain calculations can be obtained simply by referring to the LUT, without actually performing the calculations. This accelerates processing and reduces the load on a system. The LUT in an LCD monitor identifies the optimal eight-bit RGB colors from multi-gradation color data of 10 or more bits.

An overview of an internal gamma correction feature. Eight-bit RGB color information input from the PC is subjected to multi-gradation to 10 or more bits. This is then remapped to the optimal eight-bit RGB tone by referring to the LUT. Following internal gamma correction, the results approach the ideal gamma curve, dramatically improving on screen gradation and color reproduction.

Eizo Nanao"s LCD monitors proactively employ internal gamma correction features. In models designed especially for high picture quality and in some models in the ColorEdge series designed for color management, eight-bit RGB input signals from the PC are subjected to multi-gradation, and calculations are performed at 14 or 16 bits. A key reason for performing calculations at bit counts higher than the LUT bit count is to improve gradation still further, particularly the reproduction of darker tones. Users seeking high-quality color reproduction should probably choose a monitor model like this one.

In conclusion, we"ve prepared image patterns that make it easy to check the gamma values of an LCD monitor, based on this session"s discussion. Looking directly at your LCD monitor, move back slightly from the screen and gaze at the following images with your eyes half-closed. Visually compare the square outlines and the stripes around them, looking for patterns that appear to have the same tone of gray (brightness). The pattern for which the square frame and the striped pattern around it appear closest in brightness represents the rough gamma value to which the monitor is currently configured.

Based on a gamma value of 2.2, if the square frame appears dark, the LCD monitor"s gamma value is low. If the square frame appears bright, the gamma value is high. You can adjust the gamma value by changing the LCD monitor"s brightness settings or by adjusting brightness in the driver menu for the graphics card.

Naturally, it"s even easier to adjust the gamma if you use a model designed for gamma value adjustments, like an EIZO LCD monitor. For even better color reproduction, you can set the gamma value and optimize color reproduction by calibrating your monitor.

Gamma is an important but seldom understood characteristic of virtually all digital imaging systems. It defines the relationship between a pixel"s numerical value and its actual luminance. Without gamma, shades captured by digital cameras wouldn"t appear as they did to our eyes (on a standard monitor). It"s also referred to as gamma correction, gamma encoding or gamma compression, but these all refer to a similar concept. Understanding how gamma works can improve one"s exposure technique, in addition to helping one make the most of image editing.

1. Our eyes do not perceive light the way cameras do. With a digital camera, when twice the number of photons hit the sensor, it receives twice the signal (a "linear" relationship). Pretty logical, right? That"s not how our eyes work. Instead, we perceive twice the light as being only a fraction brighter — and increasingly so for higher light intensities (a "nonlinear" relationship).

Compared to a camera, we are much more sensitive to changes in dark tones than we are to similar changes in bright tones. There"s a biological reason for this peculiarity: it enables our vision to operate over a broader range of luminance. Otherwise the typical range in brightness we encounter outdoors would be too overwhelming.

But how does all of this relate to gamma? In this case, gamma is what translates between our eye"s light sensitivity and that of the camera. When a digital image is saved, it"s therefore "gamma encoded" — so that twice the value in a file more closely corresponds to what we would perceive as being twice as bright.

Technical Note: Gamma is defined by Vout = Vingamma , where Vout is the output luminance value and Vin is the input/actual luminance value. This formula causes the blue line above to curve. When gamma<1, the line arches upward, whereas the opposite occurs with gamma>1.

2. Gamma encoded images store tones more efficiently. Since gamma encoding redistributes tonal levels closer to how our eyes perceive them, fewer bits are needed to describe a given tonal range. Otherwise, an excess of bits would be devoted to describe the brighter tones (where the camera is relatively more sensitive), and a shortage of bits would be left to describe the darker tones (where the camera is relatively less sensitive):

Notice how the linear encoding uses insufficient levels to describe the dark tones — even though this leads to an excess of levels to describe the bright tones. On the other hand, the gamma encoded gradient distributes the tones roughly evenly across the entire range ("perceptually uniform"). This also ensures that subsequent image editing, color and histograms are all based on natural, perceptually uniform tones.

Despite all of these benefits, gamma encoding adds a layer of complexity to the whole process of recording and displaying images. The next step is where most people get confused, so take this part slowly. A gamma encoded image has to have "gamma correction" applied when it is viewed — which effectively converts it back into light from the original scene. In other words, the purpose of gamma encoding is for recording the image — not for displaying the image. Fortunately this second step (the "display gamma") is automatically performed by your monitor and video card. The following diagram illustrates how all of this fits together:

1. Image Gamma. This is applied either by your camera or RAW development software whenever a captured image is converted into a standard JPEG or TIFF file. It redistributes native camera tonal levels into ones which are more perceptually uniform, thereby making the most efficient use of a given bit depth.

2. Display Gamma. This refers to the net influence of your video card and display device, so it may in fact be comprised of several gammas. The main purpose of the display gamma is to compensate for a file"s gamma — thereby ensuring that the image isn"t unrealistically brightened when displayed on your screen. A higher display gamma results in a darker image with greater contrast.

3. System Gamma. This represents the net effect of all gamma values that have been applied to an image, and is also referred to as the "viewing gamma." For faithful reproduction of a scene, this should ideally be close to a straight line (gamma = 1.0). A straight line ensures that the input (the original scene) is the same as the output (the light displayed on your screen or in a print). However, the system gamma is sometimes set slightly greater than 1.0 in order to improve contrast. This can help compensate for limitations due to the dynamic range of a display device, or due to non-ideal viewing conditions and image flare.

The precise image gamma is usually specified by a color profile that is embedded within the file. Most image files use an encoding gamma of 1/2.2 (such as those using sRGB and Adobe RGB 1998 color), but the big exception is with RAW files, which use a linear gamma. However, RAW image viewers typically show these presuming a standard encoding gamma of 1/2.2, since they would otherwise appear too dark:

If no color profile is embedded, then a standard gamma of 1/2.2 is usually assumed. Files without an embedded color profile typically include many PNG and GIF files, in addition to some JPEG images that were created using a "save for the web" setting.

Technical Note on Camera Gamma. Most digital cameras record light linearly, so their gamma is assumed to be 1.0, but near the extreme shadows and highlights this may not hold true. In that case, the file gamma may represent a combination of the encoding gamma and the camera"s gamma. However, the camera"s gamma is usually negligible by comparison. Camera manufacturers might also apply subtle tonal curves, which can also impact a file"s gamma.

This is the gamma that you are controlling when you perform monitor calibration and adjust your contrast setting. Fortunately, the industry has converged on a standard display gamma of 2.2, so one doesn"t need to worry about the pros/cons of different values. Older macintosh computers used a display gamma of 1.8, which made non-mac images appear brighter relative to a typical PC, but this is no longer the case.

Recall that the display gamma compensates for the image file"s gamma, and that the net result of this compensation is the system/overall gamma. For a standard gamma encoded image file (—), changing the display gamma (—) will therefore have the following overall impact (—) on an image:

Recall from before that the image file gamma (—) plus the display gamma (—) equals the overall system gamma (—). Also note how higher gamma values cause the red curve to bend downward.

If you"re having trouble following the above charts, don"t despair! It"s a good idea to first have an understanding of how tonal curves impact image brightness and contrast. Otherwise you can just look at the portrait images for a qualitative understanding.

How to interpret the charts. The first picture (far left) gets brightened substantially because the image gamma (—) is uncorrected by the display gamma (—), resulting in an overall system gamma (—) that curves upward. In the second picture, the display gamma doesn"t fully correct for the image file gamma, resulting in an overall system gamma that still curves upward a little (and therefore still brightens the image slightly). In the third picture, the display gamma exactly corrects the image gamma, resulting in an overall linear system gamma. Finally, in the fourth picture the display gamma over-compensates for the image gamma, resulting in an overall system gamma that curves downward (thereby darkening the image).

The overall display gamma is actually comprised of (i) the native monitor/LCD gamma and (ii) any gamma corrections applied within the display itself or by the video card. However, the effect of each is highly dependent on the type of display device.

CRT Monitors. Due to an odd bit of engineering luck, the native gamma of a CRT is 2.5 — almost the inverse of our eyes. Values from a gamma-encoded file could therefore be sent straight to the screen and they would automatically be corrected and appear nearly OK. However, a small gamma correction of ~1/1.1 needs to be applied to achieve an overall display gamma of 2.2. This is usually already set by the manufacturer"s default settings, but can also be set during monitor calibration.

LCD Monitors. LCD monitors weren"t so fortunate; ensuring an overall display gamma of 2.2 often requires substantial corrections, and they are also much less consistent than CRT"s. LCDs therefore require something called a look-up table (LUT) in order to ensure that input values are depicted using the intended display gamma (amongst other things). See the tutorial on monitor calibration: look-up tables for more on this topic.

Technical Note: The display gamma can be a little confusing because this term is often used interchangeably with gamma correction, since it corrects for the file gamma. However, the values given for each are not always equivalent. Gamma correction is sometimes specified in terms of the encoding gamma that it aims to compensate for — not the actual gamma that is applied. For example, the actual gamma applied with a "gamma correction of 1.5" is often equal to 1/1.5, since a gamma of 1/1.5 cancels a gamma of 1.5 (1.5 * 1/1.5 = 1.0). A higher gamma correction value might therefore brighten the image (the opposite of a higher display gamma).

Dynamic Range. In addition to ensuring the efficient use of image data, gamma encoding also actually increases the recordable dynamic range for a given bit depth. Gamma can sometimes also help a display/printer manage its limited dynamic range (compared to the original scene) by improving image contrast.

Gamma Correction. The term "gamma correction" is really just a catch-all phrase for when gamma is applied to offset some other earlier gamma. One should therefore probably avoid using this term if the specific gamma type can be referred to instead.

Gamma Compression & Expansion. These terms refer to situations where the gamma being applied is less than or greater than one, respectively. A file gamma could therefore be considered gamma compression, whereas a display gamma could be considered gamma expansion.

Applicability. Strictly speaking, gamma refers to a tonal curve which follows a simple power law (where Vout = Vingamma), but it"s often used to describe other tonal curves. For example, the sRGB color space is actually linear at very low luminosity, but then follows a curve at higher luminosity values. Neither the curve nor the linear region follow a standard gamma power law, but the overall gamma is approximated as 2.2.

Is Gamma Required? No, linear gamma (RAW) images would still appear as our eyes saw them — but only if these images were shown on a linear gamma display. However, this would negate gamma"s ability to efficiently record tonal levels.

These cookies help to improve the performance of BenQ. If you want to opt-out of advertising cookies, you have to turn-off performance cookies. We also use Google Analytics, SessionCam and Hotjar to track activity and performance on the BenQ website. You can control the information provided to Google, SessionCam and Hotjar.  To opt out of certain ads provided by Google you can use any of the methods set forth here or using the Google Analytics opt out browser add-on here. To opt-out of SessionCam collecting data, you can disable tracking completely by following link：https://www.hotjar.com/privacy/do-not-track/.

If the gamma levels of your monitor are low, the shadows are brighter. If they’re high, the light is more luminescent. That’s why lower gamma tends to make the display washed out and flat, while higher gamma produces more contrast.

Monitors are not created equal. That’s why the ideal gamma settings depend on the kind of monitor you have. If you have a higher-end model, you’ll even have extra gamma modes, so you can further tweak your monitor’s output depending on your preference. However, the standard gamma for the sRGB color space is 2.2, which generally gives Windows accurate color results.

If you have good gamma settings, your monitor will display better image quality and depth. But poor settings will remove essential details in the shadows and highlights. You should also modify your brightness and contrast settings since they also affect the calibration of gamma.

However, you should note that most monitors won’t achieve the ideal gamma settings on their own. You need advanced color management software to ensure you get the most accurate color. Lastly, gamma levels don’t fix the blurriness of your screen. This usually comes from using the wrong resolution on your monitor.

Important reminder: Before calibrating your display, make sure it’s been running for at least 30 minutes. This guarantees that the monitor has warmed up and shows the normal brightness and colors.

On the Adjust gamma window, use the slider on the left to find the right gamma setting for your display. To do this, adjust the slider until the dots in the middle are less visible. Moving the slider changes your screen"s brightness and color, so don’t be surprised if your screen goes brighter or darker. Also, don’t worry if you can’t make the circle disappear. Just find the right setting that blends it in. Once you get the correct blend, click Next.

Unfortunately, there’s no such thing as the perfect gamma settings. The correct levels depend on your monitor and its output. However, you can still improve and modify the display depending on your preference. If you feel like your monitor is not giving you accurate color, maybe it’s time to look for a new monitor that’s perfect for your needs.

The effect of gamma correction on an image: The original image was taken to varying powers, showing that powers larger than 1 make the shadows darker, while powers smaller than 1 make dark regions lighter.

Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems.power-law expression:

Gamma encoding of images is used to optimize the usage of bits when encoding an image, or bandwidth used to transport an image, by taking advantage of the non-linear manner in which humans perceive light and color.lightness), under common illumination conditions (neither pitch black nor blindingly bright), follows an approximate power function (which has no relation to the gamma function), with greater sensitivity to relative differences between darker tones than between lighter tones, consistent with the Stevens power law for brightness perception. If images are not gamma-encoded, they allocate too many bits or too much bandwidth to highlights that humans cannot differentiate, and too few bits or too little bandwidth to shadow values that humans are sensitive to and would require more bits/bandwidth to maintain the same visual quality.floating-point images is not required (and may be counterproductive), because the floating-point format already provides a piecewise linear approximation of a logarithmic curve.

Although gamma encoding was developed originally to compensate for the input–output characteristic of cathode ray tube (CRT) displays, it is not its main purpose or advantage in modern systems. In CRT displays, the light intensity varies nonlinearly with the electron-gun voltage. Altering the input signal by gamma compression can cancel this nonlinearity, such that the output picture has the intended luminance. However, the gamma characteristics of the display device do not play a factor in the gamma encoding of images and video. They need gamma encoding to maximize the visual quality of the signal, regardless of the gamma characteristics of the display device.

Analogously, digital cameras record light using electronic sensors that usually respond linearly. In the process of rendering linear raw data to conventional RGB data (e.g. for storage into JPEG image format), color space transformations and rendering transformations will be performed. In particular, almost all standard RGB color spaces and file formats use a non-linear encoding (a gamma compression) of the intended intensities of the primary colors of the photographic reproduction. In addition, the intended reproduction is almost always nonlinearly related to the measured scene intensities, via a tone reproduction nonlinearity.

That is, gamma can be visualized as the slope of the input–output curve when plotted on logarithmic axes. For a power-law curve, this slope is constant, but the idea can be extended to any type of curve, in which case gamma (strictly speaking, "point gamma"

When a photographic film is exposed to light, the result of the exposure can be represented on a graph showing log of exposure on the horizontal axis, and density, or negative log of transmittance, on the vertical axis. For a given film formulation and processing method, this curve is its characteristic or Hurter–Driffield curve.

Output to CRT-based television receivers and monitors does not usually require further gamma correction. The standard video signals that are transmitted or stored in image files incorporate gamma compression matching the gamma expansion of the CRT (although it is not the exact inverse).

For television signals, gamma values are fixed and defined by the analog video standards. CCIR System M and N, associated with NTSC color, use gamma 2.2; the rest (systems B/G, H, I, D/K, K1 and L) associated with PAL or SECAM color, use gamma 2.8.

In most computer display systems, images are encoded with a gamma of about 0.45 and decoded with the reciprocal gamma of 2.2. A notable exception, until the release of Mac OS X 10.6 (Snow Leopard) in September 2009, were Macintosh computers, which encoded with a gamma of 0.55 and decoded with a gamma of 1.8. In any case, binary data in still image files (such as JPEG) are explicitly encoded (that is, they carry gamma-encoded values, not linear intensities), as are motion picture files (such as MPEG). The system can optionally further manage both cases, through color management, if a better match to the output device gamma is required.

Plot of the sRGB standard gamma-expansion nonlinearity in red, and its local gamma value (slope in log–log space) in blue. The local gamma rises from 1 to about 2.2.

The sRGB color space standard used with most cameras, PCs, and printers does not use a simple power-law nonlinearity as above, but has a decoding gamma value near 2.2 over much of its range, as shown in the plot to the right. Below a compressed value of 0.04045 or a linear intensity of 0.00313, the curve is linear (encoded value proportional to intensity), so γ = 1. The dashed black curve behind the red curve is a standard γ = 2.2 power-law curve, for comparison.

Gamma correction in computers is used, for example, to display a gamma = 1.8 Apple picture correctly on a gamma = 2.2 PC monitor by changing the image gamma. Another usage is equalizing of the individual color-channel gammas to correct for monitor discrepancies.

Some picture formats allow an image"s intended gamma (of transformations between encoded image samples and light output) to be stored as metadata, facilitating automatic gamma correction as long as the display system"s exponent is known. The PNG specification includes the gAMA chunk for this purposeJPEG and TIFF the Exif Gamma tag can be used.

These features have historically caused problems, especially on the web. There is no numerical value of gamma that matches the "show the 8-bit numbers unchanged" method used for JPG, GIF, HTML, and CSS colors, so the PNG would not match.Google Chrome (and all other Chromium-based browsers) and Mozilla Firefox either ignore the gamma setting entirely, or ignore it when set to known wrong values.

A gamma characteristic is a power-law relationship that approximates the relationship between the encoded luma in a television system and the actual desired image luminance.

With this nonlinear relationship, equal steps in encoded luminance correspond roughly to subjectively equal steps in brightness. Ebner and Fairchildused an exponent of 0.43 to convert linear intensity into lightness (luma) for neutrals; the reciprocal, approximately 2.33 (quite close to the 2.2 figure cited for a typical display subsystem), was found to provide approximately optimal perceptual encoding of grays.

The following illustration shows the difference between a scale with linearly-increasing encoded luminance signal (linear gamma-compressed luma input) and a scale with linearly-increasing intensity scale (linear luminance output).

On most displays (those with gamma of about 2.2), one can observe that the linear-intensity scale has a large jump in perceived brightness between the intensity values 0.0 and 0.1, while the steps at the higher end of the scale are hardly perceptible. The gamma-encoded scale, which has a nonlinearly-increasing intensity, will show much more even steps in perceived brightness.

A cathode ray tube (CRT), for example, converts a video signal to light in a nonlinear way, because the electron gun"s intensity (brightness) as a function of applied video voltage is nonlinear. The light intensity I is related to the source voltage Vs according to

where γ is the Greek letter gamma. For a CRT, the gamma that relates brightness to voltage is usually in the range 2.35 to 2.55; video look-up tables in computers usually adjust the system gamma to the range 1.8 to 2.2,

For simplicity, consider the example of a monochrome CRT. In this case, when a video signal of 0.5 (representing a mid-gray) is fed to the display, the intensity or brightness is about 0.22 (resulting in a mid-gray, about 22% the intensity of white). Pure black (0.0) and pure white (1.0) are the only shades that are unaffected by gamma.

To compensate for this effect, the inverse transfer function (gamma correction) is sometimes applied to the video signal so that the end-to-end response is linear. In other words, the transmitted signal is deliberately distorted so that, after it has been distorted again by the display device, the viewer sees the correct brightness. The inverse of the function above is

where Vc is the corrected voltage, and Vs is the source voltage, for example, from an image sensor that converts photocharge linearly to a voltage. In our CRT example 1/γ is 1/2.2 ≈ 0.45.

A color CRT receives three video signals (red, green, and blue) and in general each color has its own value of gamma, denoted γR, γG or γB. However, in simple display systems, a single value of γ is used for all three colors.

Other display devices have different values of gamma: for example, a Game Boy Advance display has a gamma between 3 and 4 depending on lighting conditions. In LCDs such as those on laptop computers, the relation between the signal voltage Vs and the intensity I is very nonlinear and cannot be described with gamma value. However, such displays apply a correction onto the signal voltage in order to approximately get a standard γ = 2.5 behavior. In NTSC television recording, γ = 2.2.

The power-law function, or its inverse, has a slope of infinity at zero. This leads to problems in converting from and to a gamma colorspace. For this reason most formally defined colorspaces such as sRGB will define a straight-line segment near zero and add raising x + K (where K is a constant) to a power so the curve has continuous slope. This straight line does not represent what the CRT does, but does make the rest of the curve more closely match the effect of ambient light on the CRT. In such expressions the exponent is not the gamma; for instance, the sRGB function uses a power of 2.4 in it, but more closely resembles a power-law function with an exponent of 2.2, without a linear portion.

Up to four elements can be manipulated in order to achieve gamma encoding to correct the image to be shown on a typical 2.2- or 1.8-gamma computer display:

The pixel"s intensity values in a given image file; that is, the binary pixel values are stored in the file in such way that they represent the light intensity via gamma-compressed values instead of a linear encoding. This is done systematically with digital video files (as those in a DVD movie), in order to minimize the gamma-decoding step while playing, and maximize image quality for the given storage. Similarly, pixel values in standard image file formats are usually gamma-compensated, either for sRGB gamma (or equivalent, an approximation of typical of legacy monitor gammas), or according to some gamma specified by metadata such as an ICC profile. If the encoding gamma does not match the reproduction system"s gamma, further correction may be done, either on display or to create a modified image file with a different profile.

The rendering software writes gamma-encoded pixel binary values directly to the video memory (when highcolor/truecolor modes are used) or in the CLUT hardware registers (when indexed color modes are used) of the display adapter. They drive Digital-to-Analog Converters (DAC) which output the proportional voltages to the display. For example, when using 24-bit RGB color (8 bits per channel), writing a value of 128 (rounded midpoint of the 0–255 byte range) in video memory it outputs the proportional ≈ 0.5 voltage to the display, which it is shown darker due to the monitor behavior. Alternatively, to achieve ≈ 50% intensity, a gamma-encoded look-up table can be applied to write a value near to 187 instead of 128 by the rendering software.

Modern display adapters have dedicated calibrating CLUTs, which can be loaded once with the appropriate gamma-correction look-up table in order to modify the encoded signals digitally before the DACs that output voltages to the monitor.hardware calibration.

Some modern monitors allow the user to manipulate their gamma behavior (as if it were merely another brightness/contrast-like setting), encoding the input signals by themselves before they are displayed on screen. This is also a calibration by hardware technique but it is performed on the analog electric signals instead of remapping the digital values, as in the previous cases.

In a typical system, for example from camera through JPEG file to display, the role of gamma correction will involve several cooperating parts. The camera encodes its rendered image into the JPEG file using one of the standard gamma values such as 2.2, for storage and transmission. The display computer may use a color management engine to convert to a different color space (such as older Macintosh"s γ = 1.8 color space) before putting pixel values into its video memory. The monitor may do its own gamma correction to match the CRT gamma to that used by the video system. Coordinating the components via standard interfaces with default standard gamma values makes it possible to get such system properly configured.

This procedure is useful for making a monitor display images approximately correctly, on systems in which profiles are not used (for example, the Firefox browser prior to version 3.0 and many others) or in systems that assume untagged source images are in the sRGB colorspace.

In the test pattern, the intensity of each solid color bar is intended to be the average of the intensities in the surrounding striped dither; therefore, ideally, the solid areas and the dithers should appear equally bright in a system properly adjusted to the indicated gamma.

Normally a graphics card has contrast and brightness control and a transmissive LCD monitor has contrast, brightness, and backlight control. Graphics card and monitor contrast and brightness have an influence on effective gamma, and should not be changed after gamma correction is completed.

Given a desired display-system gamma, if the observer sees the same brightness in the checkered part and in the homogeneous part of every colored area, then the gamma correction is approximately correct.

Before gamma correction the desired gamma and color temperature should be set using the monitor controls. Using the controls for gamma, contrast and brightness, the gamma correction on an LCD can only be done for one specific vertical viewing angle, which implies one specific horizontal line on the monitor, at one specific brightness and contrast level. An ICC profile allows one to adjust the monitor for several brightness levels. The quality (and price) of the monitor determines how much deviation of this operating point still gives a satisfactory gamma correction. Twisted nematic (TN) displays with 6-bit color depth per primary color have lowest quality. In-plane switching (IPS) displays with typically 8-bit color depth are better. Good monitors have 10-bit color depth, have hardware color management and allow hardware calibration with a tristimulus colorimeter. Often a 6bit plus FRC panel is sold as 8bit and a 8bit plus FRC panel is sold as 10bit. FRC is no true replacement for more bits. The 24-bit and 32-bit color depth formats have 8 bits per primary color.

With Microsoft Windows 7 and above the user can set the gamma correction through the display color calibration tool dccw.exe or other programs.ICC profile file and load it as default. This makes color management easy.color Look Up Table correctly after waking up from standby or hibernate mode and show wrong gamma. In this case update the graphics card driver.

On some operating systems running the X Window System, one can set the gamma correction factor (applied to the existing gamma value) by issuing the command xgamma -gamma 0.9 for setting gamma correction factor to 0.9, and xgamma for querying current value of that factor (the default is 1.0). In macOS systems, the gamma and other related screen calibrations are made through the System Preferences.

The test image is only valid when displayed "raw", i.e. without scaling (1:1 pixel to screen) and color adjustment, on the screen. It does, however, also serve to point out another widespread problem in software: many programs perform scaling in a color space with gamma, instead of a physically-correct linear space. In a sRGB color space with an approximate gamma of 2.2, the image should show a "2.2" result at 50% size, if the zooming is done linearly. Jonas Berlin has created a "your scaling software sucks/rules" image based on the same principle.

In addition to scaling, the problem also applies to other forms of downsampling (scaling down), such as chroma subsampling in JPEG"s gamma-enabled Y′CbCr.WebP solves this problem by calculating the chroma averages in linear space then converting back to a gamma-enabled space; an iterative solution is used for larger images. The same "sharp YUV" (formerly "smart YUV") code is used in sjpeg. Kornelski provides a simpler approximation by luma-based weighted average.Alpha compositing, color gradients, and 3D rendering are also affected by this issue.

Paradoxically, when upsampling (scaling up) an image, the result processed in the "wrong" gamma-enabled space tends to be more aesthetically pleasing. This is because upscaling filters are tuned to minimize the ringing artifacts in a linear space, but human perception is non-linear and better approximated by gamma. An alternative way to trim the artifacts is using a sigmoidal light transfer function, a technique pioneered by GIMP"s LoHalo filter and later adopted by madVR.

The term intensity refers strictly to the amount of light that is emitted per unit of time and per unit of surface, in units of lux. Note, however, that in many fields of science this quantity is called luminous exitance, as opposed to luminous intensity, which is a different quantity. These distinctions, however, are largely irrelevant to gamma compression, which is applicable to any sort of normalized linear intensity-like scale.

One contrasts relative luminance in the sense of color (no gamma compression) with luma in the sense of video (with gamma compression), and denote relative luminance by Y and luma by Y′, the prime symbol (′) denoting gamma compression.

Gamma correction is a type of power law function whose exponent is the Greek letter gamma (γ). It should not be confused with the mathematical Gamma function. The lower case gamma, γ, is a parameter of the former; the upper case letter, Γ, is the name of (and symbol used for) the latter (as in Γ(x)). To use the word "function" in conjunction with gamma correction, one may avoid confusion by saying "generalized power law function".

Without context, a value labeled gamma might be either the encoding or the decoding value. Caution must be taken to correctly interpret the value as that to be applied-to-compensate or to be compensated-by-applying its inverse. In common parlance, in many occasions the decoding value (as 2.2) is employed as if it were the encoding value, instead of its inverse (1/2.2 in this case), which is the real value that must be applied to encode gamma.

McKesson, Jason L. "Chapter 12. Dynamic Range – Linearity and Gamma". Learning Modern 3D Graphics Programming. Archived from the original on 18 July 2013. Retrieved 11 July 2013.

"11A: Characteristics of systems for monochrome and color television". Reports of the CCIR, 1990: Also Decisions : XVIIth Plenary Assembly, Dusseldorf (PDF). International Radio Consultative Committee. 1990.

Fritz Ebner and Mark D Fairchild, "Development and testing of a color space (IPT) with improved hue uniformity," Proceedings of IS&T/SID"s Sixth Color Imaging Conference, p 8-13 (1998).

Koren, Norman. "Monitor calibration and gamma". Retrieved 2018-12-10. The chart below enables you to set the black level (brightness) and estimate display gamma over a range of 1 to 3 with precison better than 0.1.

Nienhuys, Han-Kwang (2008). "Gamma calibration". Retrieved 2018-11-30. The reason for using 48% rather than 50% as a luminance is that many LCD screens have saturation issues in the last 5 percent of their brightness range that would distort the gamma measurement.

Andrews, Peter. "The Monitor calibration and Gamma assessment page". Retrieved 2018-11-30. the problem is caused by the risetime of most monitor hardware not being sufficiently fast to turn from full black to full white in the space of a single pixel, or even two, in some cases.

Werle, Eberhard. "Quickgamma". Retrieved 2018-12-10. QuickGamma is a small utility program to calibrate a monitor on the fly without having to buy expensive hardware tools.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

Note: Ensure to set your LCD panel to factory settings at this point. Otherwise, you will not get the best results. To reset your LCD panel to factory conditions, use the buttons that are located on the front, side, or back. However, if your LCD panel lets you set the gamma, you should set it to 2.2 or as close as possible.

Next, use the slider to adjust the gamma. To do this, move the slider until the dots in the middle of the image appear less visible. This changes both the brightness and color of your screen.

Note: Do not worry if you cannot make the circles in the center completely disappear. If you want a better way of testing, you can also use this gamma correction test image. Try to make as many numbers appear on the top and bottom bars as possible. With better LCD panel s, you can see 6 numbers in each bar, while lower-grade LCD panel s will only be able to show 4 numbers.

Note: If you cannot adjust the slider, you might have to change the gamma settings by using your LCD panel ’s controls. You should still keep the display settings window and gamma correction image test open while you do this.

Next, adjust the brightness. To do this, use the control buttons on your LCD panel until you can see the shirt and suit in the image, but not so much that the X stands out from the background. You should still be able to see the "X," but the wall behind it should not be washed out.

Note: Your screen looks different depending on what angle you are looking at it. For the best results, you should step back and look at your LCD panel from far away.

Next, adjust the contrast. To do this, use the buttons on your LCD panel. You want to set your contrast so you can just see the wrinkles and buttons on the shirt of the man in the figure. The background of the image should not be bright white.

If you are satisfied with the new calibration, click Finish. If not, click Cancel, and you can start all over. To get the best results, you can do the steps over again. For best results, you might want to go through the steps again, but backward this time. This is because each step affects the next one, so changing the order helps you fine-tune your calibration even more.

There"s a dark art called color management that can fix those problems, but it comes with a cost: around $150 for a monitor calibration tool (Calibrite ColorChecker Display or Datacolor SpyderX Pro are both excellent) plus some investment in knowledge to get the most out of it.

Let me admit my bias up front: Hi, my name is Fabio and I"m a color nerd. Buying a monitor calibration tool is a must for any creative professional who depends on accurate color and I"d love to convince you of that.

If we look up the reviews for the most popular hardware monitor calibration devices on Amazon we"ll see a lot of angry users complaining about color casts and bad results overall.

Instead of just saying "go out and buy one of those spider thingies", let"s discuss briefly what is color management and how can we get better color from our monitors just by understanding and selecting the right settings.

Consider this guide as the first step for getting more accurate colors from your existing display. All these recommendations remain valid and will serve as a good starting point for a professional color calibration later on.

In practice: if you have custom color profiles for your monitor and photo printer, Adobe Lightroom can understand their differences and match their output as closely as possible, or simulate the printer output on your screen.

There"s no way around it. Visual calibration tools, like those included on Windows, MacOS or free software like Calibrize, are very limited since they rely on our eyes for the correction and everyone perceives color differently.

First one, and what I"d recommend, is to adopt a partially color managed workflow, starting with a properly calibrated LCD monitor with an IPS type screen. The least expensive monitor calibration tools I recommend are the Calibrite ColorChecker Display (in-depth review) and Datacolor SpyderX Pro (in-depth review).

Calibrite ColorChecker Display, Pro and Plus models are just rebranded versions of X-Rite i1Display Studio, Pro and Pro Plus, respectively. Keep an eye on discounts for the previous versions. They use the same software and work exactly the same.

By using a calibrated monitor, it"s possible to tame the most variable component in the color workflow and the biggest source for errors. Calibrating your screen ensures that what you see is consistent from day to day and any work based on it can be delivered with accurate colors, no matter the output medium, from the web to printed pieces.

On the output side, printer profiles have come a long way in the past decade. Most high end inkjet printers drift very little from the factory calibration and offer good enough canned profiles for popular paper combinations.

Commercial printers usually follow a known standard and the best practice is to deliver files in the color space recommended, usually AdobeRGB for fine art inkjet printing. In other words, the output file is color-agnostic. It doesn"t need to know how the printer reproduces color. That"s the provider"s responsibility and by using color management the file colors will be accurately reproduced by the output device as expected.

More often than not monitors come from factory set up not to be accurate, but to look good on the showroom floors. Vibrant and punchy colors are generally far from accurate.

It"s ok to enjoy a super saturated display for content consumption or gaming, but for creative work, photography, video, etc, the best color response possible is the most boring and repeatable one.

Factory calibration doesn"t eliminate the need for custom color profiles. That"s a common misconception. What it means is that each piece of hardware is individually adjusted in factory and will deviate less from a standard than an uncalibrated model. In practice, we can trust the sRGB color preset on a calibrated monitor will be close to that matching color space.

Ideally we want the calibration process and resulting color profile to do the least amount of work possible for the best final results. It"s always better to get it close as close as possible to the calibration target in hardware, instead of relying on the color profile alone for doing heavy corrections.

This strategy is similar to what colorists use to calibrate monitors for color grading. On the high end video world, the gold standard is to use a reference display that matches as perfectly as possible a known color standard. Some workflows don"t even use color management.

If having a bit of color inaccuracy is acceptable, maybe that money will be better spent elsewhere. For example, illustrators often don"t need to work with precise colors as everything is up to their creative interpretation.

Based on my tests, modern monitors drift very little over time. For less demanding work, calibrating a modern good quality IPS monitor twice a year is perfectly acceptable for most use cases.

Not all displays offer the settings necessary to adjust color response. Laptops, MacBooks, iMacs and most computers with integrated monitors offer only a single setting to adjust the luminance or brightness of the display backlight. Color temperature, gamma and color gamut are locked at the factory setting.

Thankfully, computer monitors are getting better at each day and there"s a noticeable market movement to adopt color accuracy as a selling proposition, specially on more expensive laptops and all-in-one computers like iMacs.

Most of those displays are close to the settings we want: 6500K white point with 2.2 gamma. Apple is at the forefront by adopting wide gamut displays with a DCI-P3 gamut on all devices.

If your display doesn"t offer hardware controls for color, it"s still important to adjust the panel brightness and match it to the working environment, as described below. Also remember to disable auto brightness, night shift and any other software function that can alter the display color response.

There are good inexpensive monitors at the $300 mark with factory calibration and advanced hardware controls, but that"s not always an upgrade. Apple"s newer wide gamut monitors are really good and will be noticeably better than a $300 one in terms of color gamut and resolution. For those cases, investing in a monitor calibration tool would make more sense.

Step one is to reset the monitor to factory defaults and begin with a clean slate. It"s also important to let it warm up for 30 minutes to ensure color response and brightness are stable.

The luminance or backlight brightness setting adjusts the intensity of the light projected by the monitor through the LCD layers that make each primary color. In other words, it controls how bright the monitor will look.

Our goal here is to match room and monitor lighting so both look balanced. For the best results in professional environments it"s also important to match the room lights" color temperature and even the wall colors. Our eye adapts to the surrounding environment and all those factors can alter the perception of color.

The ideal luminance range for color accurate work ranges from 80 cd/m2 to 140 cd/m2 or nits. But that"s only possible to measure with a hardware device, either a colorimeter or spectrophotometer.

Without a colorimeter, the best guidance is to match monitor and room brightness in a way that neither looks too bright compared to the other. Always avoid cranking up backlight brightness too high unless there"s a good reason for it.

Most people tend to run their monitors too bright and the recommended values may seem dim at first, but that"s the range that can more closely match a printed photograph and the eyes quickly adapt to it.

The simple explanation is that gamma is a correction curve used to distribute the intermediate tones in an image. A gamma curve of 2.2 more closely matches our visual perception of tones and is the most common standard used for photo editing, design or general computer usage.

In the past, Mac computers had a default gamma value of 1.8 which matches more closely commercial printing, but nowadays MacOS uses gamma 2.2 just like Windows and most other operating systems.

It was very common 15 years ago for computer monitors to have high native white points, looking very cool compared to natural lighting, specially the first affordable LCD displays. LED backlights evolved a lot since then and most monitors nowadays are close to 6500K.

The most common monitor native color temperature, also called white point, is 6500K. That"s the color temperature used on the two most popular standards for monitor color: sRGB and rec. 709 (ITU-R BT.709).

Rec. 709, also known as Rec.709, BT.709, and ITU 709, is a standard developed by ITU-R for characterizing color response in HD television. It"s the most common standard for video. Primary color coordinates are identical to sRGB, as is the white point at D65 (effectively 6500K), but the gamma curve is different.

Don"t worry if you"re working on a screen without color temperature controls, laptops or iMacs, for example. Most modern good quality LCDs are close to 6500K.

Using 6500K is a great starting point, but there are reasons to stray from it in special cases. For example, a slightly lower color temperature around 5500K can provide a better screen to print match for your particular work environment.

For simplicity"s sake, we can safely assume that the 6500K preset on the monitor is the one that will match more closely the D65 theoretical color used on those standards.

Most standalone monitors have controls for color gamut. We"ll usually find at least a sRGB preset and individual red, green and blue controls to run it on the unconstrained native gamut. Wide gamut displays often have additional options, such as AdobeRGB and DCI-P3.

Setting up the monitor on a wide gamut preset, such as DCI-P3, but not using color management is the cause for oversaturated monitor colors. The operating system will treat that device as sRGB, but the actual gamut is much larger. In other words, a saturated red color on a wide gamut display is much more vibrant than on a sRGB one and without a custom ICC profile the OS cannot compensate for it.

Sometimes monitors offer dynamic modes that can alter contrast or color response based on the content displayed. That"s a bad idea for color critical work and the opposite of what we want, which is having constant and repeatable color.

Same for modes that cut blue light. On the same note, make sure to disable Night Shift and auto brightness modes on the MacOS settings and the equivalent options on Windows 10 with the Night light and auto brightness settings.

Do not touch the contrast control and leave it at the default setting. Changing contrast internally often means clipping the darkest or lightest tones, losing information from those areas.

HDR modes are fine for consuming content, watching videos and playing games, but often hurt color accuracy and our own tonal perception when creating content.

Video editors and colorists working on the larger Rec. 2020 colorspace might benefit from HDR monitors, but that"s opening a whole new can of worms. If your work falls into this category, look into high end monitors that are VESA Certified DisplayHDR 1000 or higher.

It"s also possible to use the manufacturer supplied generic profile for that particular monitor model. Windows tends to download and assign that profile automatically, while MacOS uses the monitor EDID information to generate a neutral monitor profile based on the hardware characteristics.

Either way, always test both options and see what it works best for your particular monitor. It"s hard to say what will work best and, to be honest, we"re flying blind without actually measuring the monitor characteristics.

Physical DISPLAYS for Rec709 are defined as a gamma of 2.4. Note that this is different than the reciprocal gamma that the signal is encoded with. The sRGB spec may indicate ~2.2, but there"s more to the story.

If this is fed into a monitor with a gamma of 2.4, for a total system gamma gain of 1.1. Why is this often the case? For sRGB per the IEC standard, the monitor"s luminance is speced at 80 cd/m2. That was way back when, when CRT monitors had a hard time displaying brighter. Today LCD monitors can easily be set to 200 cd/m2 or more, and phones are available as high as 1200 d/m2 !

If you set your monitor brighter you are almost certainly going to set the monitor"s gamma higher as well. Studies have shown that typical users have their monitors set over 160 cd/m2, and gamma much higher than 2.2 to 2.4 - one survey found that over 50% of users had the gamma at 2.5 and HIGHER!

The transfer curve of the sRGB signal is "close to" a 2.2 gamma, but it is actually a piecewise curve, that is actually a higher gamma at the top end of the video range and a lower gamma at the bottom of the video range.

If you are in a bright environment with a dark monitor (peak white at 80 cd/m2 or lower), then you"ll want your display gamma lower (i.e. 2.2) as that will brighten the image to compensate for the ambient, but unfortunately also reduce contrast.

If you increase the monitor"s peak white level (say to 200cd/m2), you"ll also want the gamma higher like 2.4 which will darken the midrange and increase contrast, which is needed due to the higher ambient lighting "washing out" the blacks.

For Rec709"s BT1886 (monitor) and BT.2035 (viewing environment) the monitor gamma is 2.4, the whitepoint luminance is 100 cd/m2 and the ambient is 10 LUX (dark!)

So, how should you set your gamma? It depends on what you are doing, your environment, and if your monitor has an internal LUT (like a high end NEC or Eizo).

If you are using color management, then setting the monitor to a NATIVE gamma (i.e. relying on it"s internal LUT), and profiling it with an XRite i1 Display Pro leads to good results.

And my Samsung 245t monitors needs hardware (front panel control) tweaking to get their "native" values in line with reality for a reasonably flat profile relative to sRGB.

For all our products, we have a simple goal: to enrich your digital life. Our exclusive software enhances sound, vision and touch to give you a truly incredible experience. Enjoy it!

ASUS has a great range of exclusive apps specially created to enhance your ASUS laptop. These include useful tools and utilities for your everyday computing, apps to enhance your entertainment experience, and productivity-enhancing software. All these apps are designed to give you a fun and productive experience with your ASUS la