Adobe Gamma Setting3/23/2021
However, the monitors extra bits do let you calibrate the display to a specific white point and gamma without the losses you get with the much more common 8-bit video card LUT.If your monitor profile doesnt accurately describe the actual behavior of your monitor, your judgments about your images wont be accurate, which means your corrections will also be inaccurate.
Photoshop always uses the monitor profile used by the operating system. In Mac OS X, this is in the Displays preference; in Windows its in the Display Properties control panel. The great benefit of this approach is that it makes it possible for people using very different monitors on different platforms to view the same image as consistently as possible. This makes monitor calibration a mission-critical necessity (The only time this behavior doesnt happen is if you set the working space to Monitor RGB, which is not recommended.). To display color accurately, Photoshop needs to know how your monitor behaveswhat color white it produces, what sort of tonal response it has, and what actual colors it produces when its fed pure R, G, or B. Although a default display profile is assigned to your monitor by your operating system, youll get the best results from a profile customized for your specific monitor. Monitors drift over time, and though LCDs tend to drift much more slowly than CRTs, a profile that was accurate when it was created may not be accurate a week or a month later. Adobe Gamma Setting Update Their MonitorProfessionals whose jobs depend on accurate color may decide to update their monitor profile every week or two; some people go for a month or more before updating the profile. A profile basically describes the difference between the standard and what the hardware can actually achieve, so that the color management system can make up the difference when sending the image to the video card. For practical monitor calibration purposes, you can treat 5000 K and D50, or 6500 K and D65, as interchangeable. LCD displays have a fixed contrast ratio, so the black luminance depends entirely on the white luminance. You can calibrate any display by changing the lookup tables in the video card that drives it, but the weakness in this approach is that most video card lookup tables (LUTs) use 8 bits per channel. Just as with image editing, making adjustments always results in fewer levels than when you started, so when you only have 8 bits per channel, you need to preserve levels by putting the 8 bits per channel through as few adjustments as possible. Most professional LCD monitors have no physical adjustments other than the brightness of the backlight. ![]() Youll find guidance on setting the backlight level in Setting Aim Points, later in this chapter. Dont use them Theyre only there to pad out the feature list and provide the same convenience as CRT monitors, but in a color-critical workflow theyll probably degrade image quality, not enhance it. This is because those controls typically add an 8-bit adjustment step to your calibration and profiling routine, and you dont want to add more conversions. Even if you did, you wouldnt want them happening at only 8 bits per channel. Just leave such a monitor at its native settings, adjust only the backlight, and let your calibration and profiling package do the rest. Some high-end LCD monitorsnotably the EIZO FlexScan and ColorEdge seriescontain their own lookup tables, independent of the video card, with 10, 12, or even 14 bits of precision. Having those extra bits doesnt automatically mean the monitor displays more colors because Photoshop, the operating system, the video card, and the video port all need to carry more than 8 bits per channel of video data to the display. As long as any link in that chain supports just 8 bits per channel, youve still got an 8-bit pipeline.
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