My path of discovery regarding computer screen (display or monitor) calibration which helped me form my opinion about the subject follows, though I am not an authority. However, I hope it helps to inform you and give you some insights. If you have come this far, in your internet search, then you have already discovered there are many touts or colour calibration aficionados, to be found on various photography website forums. Too bad they cannot rush over to where your computer screen is located to colour calibrate it, and worse, it is too bad they cannot agree which is the best setting or colour space to use. Merely take a look at debates about Adobe RGB versus sRGB and then throw ProPhoto RGB into the mix. If you can prove me wrong with scientific evidence, I am willing to change my opinion, but I will not discard my monitor, as a result. Wouldn’t it be an ideal world if all computer screens from America to Zimbabwe were calibrated precisely to the same specifications, new-out-of-the-box. The fact is, they are not. All of the following will affect how colours are rendered on your computer screen. For example, if the quality of components used by one manufacturer is less than another manufacturer or quality control is lacking from one manufacturer to the next. If a screen uses CRT, LED, LCD, or Plasma technology, screen calibration will be different between each. If the video card, inside one computer is different from another, the colour calibration will be different, between the two screens. The temperature of the screen and the components affects screen calibration. The age of a screen also has an effect on colour, thus screen calibration should be periodically updated. If your screen has not been calibrated, at all, or is not calibrated to the same standard as mine or uses a different technology than mine, what you will see will be different from what I see on my screen, which only becomes apparent when the two screens are side-by-side, on the same desk. Also, if you are unaware, photos can look different that are sent across the internet when viewed by you, depending on which internet browser you use, such as Internet Explorer versus Firefox or Safari. There are “Browser Plug-ins or ways to manipulate the Browser to give similar results. Thus, when I send you a photo that looks perfect to me, it might have a colour cast or look like utter rubbish on your screen. The above explains some of the possible reasons why.
The retina of the human eye has three colour receptor cone cells, responsible for colour vision, with some amount of illumination. Red Green and Blue (RGB). For a description of how the human eye functions, please refer to this description.
In 1931, Commission Internationale de l’Éclairage (CIE) developed a gamut of colours perceptible to the human eyes, in chart form. So, I think it would be fair to say that any photographic medium, whether it is film or a digital sensor should be able to capture and faithfully reproduce these colours, in the first instance. Without any artistic interpretation or rendering applied, you should be able to hold the photograph up to the scene or this colour gamut and both should look the same. Don’t you think? When viewing the photograph on your computer screen, the computer screen should faithfully render this gamut of colours, captured with your camera, assuming the film was developed to the same standard or the correct White Balance in the digital camera had been set. If you calibrate your screen, then it should be your objective to have your screen display as wide an area of this colour gamut as possible, and as accurately as possible. Does this seem reasonable?
Using a simplistic approach, your screen should be calibrated correctly if you compare the colours of the X-rite GretagMacbeth ColorChecker (in hand) against the image below. Each colour patch has a specific value. Red is defined by setting each of the Red Green and Blue Channels, thus: 174, 54, 60, in sRGB Colour Space at 6,500°Kelvin. Green would be set to: 70, 148, 73. And, Blue would be set to: 56, 61, 150. Stark White would be set at: 255, 255, 255 And, absolute Black would be set at: 0, 0, 0.
In the image below, if you cannot see each gradation from White to Black or Black to White, for each of the four perimeter strips, then adjust Brightness, Contrast or Tilt, as necessary.
There is no substitute for a using a hardware screen calibration device and its software. I can strongly recommend DataColor Spyder 3.0 Elite, version 4.0, or the latest iteration. I have used DataColor products for some years, by now. It works, though you must try different settings, including the recommended settings. Which is 100% correct, optimum, or ideal? I cannot tell you. However, I attempt to use settings that will give me the as wide an area of the above colour gamut as possible. Each of us perceives colours differently, regardless. You will surely discover when you print your favourite photo. Oh, by the way, has your Printer been calibrated? Another can of worms. And, what is your camera set to? Auto White Balance, Preset, or Colour Temperature? What Picture Control is set? Standard, Neutral, Vivid, Portrait or Landscape? Each of the aforementioned will affect your colour rendering and what you see on screen or in print. Wasn’t film great? I trusted all this to a professional photo processing lab and still managed to get published in a magazine, month after month, for several years, using a 35mm film camera.
That said, there are plenty of variables which will yield different results, such as Black Luminance, White Luminance, Native White Point, Black Point, Visual Mode, Measured Mode, Gamma 1.8 (typical for older Windows Operating System PCs), Gamma 2.0, Gamma 2.2 (typical for Apple MAC Operating System and modern PCs) and 6500°Kelvin (a widely used setting), optionally, 5800°Kelvin, 5000°Kelvin, et cetera. Shouldn’t there be one optimum setting for each computer screen from each manufacturer that will yield the same results, around the world, accurately and faithfully? A photo of a Purple flower on my computer screen should look precisely the same in your computer screen. Purple is defined as a combination of the Red Green and Blue Channels set at 90, 60, and 108, respectively. That is the point of setting White Balance, in-camera, and Colour Calibration of your computer screen, so what you see and what I see are the same, whether we are using an iMac, a Dell, or an Eizo screen.
Regarding the debate about matte screen versus glossy screen monitors, I say to each his own. Makes no difference to my eyes. I actually find viewing and manipulating fine details, in a photo, when viewed on a glossy screen easier to work with, in a room with very dim or no light and certainly no light reflecting onto the screen.
Note 1: My calibration was done for Native White Point, 2.0 Gamma (which yielded 20.7, but 2.29 uncalibrated), Brightness Control Slider set for 90 (which yielded 90.6, but 90.5 uncalibrated -Go figure), Black Luminance Target 0.20, White Luminance Target 90
Note 2: It is unlikely that you can achieve a proper colour calibration of the iMac using the software in the Display Preferences.
Note 3: I have asked Apple Technical Support and DataColor for their recommendations about settings to use. I received no advice from Apple and DataColor suggested I go with “Recommended” settings. I discovered that the “Recommended” settings (Gamma 2.2, and 6500°Kelvin) made the iMac screen look too warm and dull. The area covered on the Colour Gamut Chart was much smaller than my settings.