loveorola 发表于 2013-1-12 21:16
gamma就是CMYK色彩空间里的TRC（色调转移曲线）在RGB色彩空间的令一种名称。 至于gamma的选取还是根据显示器本身的定位来选吧，专业级别显示器目前用gamma用L＊，普遍的用2.2，或者根据自己软件的色彩工作空间的gamma作统一。不必为gamma值过分纠结。

关于profile的类型，LUT或者matrix，楼主再好好看看书吧，你还没彻底理解。再现意图就是gumut mapping的方式，LUT只是把不同再现意图表格化了而已，matrix也是有再现意图的

2002bjbj 发表于 2013-1-12 18:27
校色这个事，没有EIZO CG之类的显示器只能是先凑合凑合，楼主的研究精神可嘉。前一段搞校色走火入魔的路过。。。。

myliyifei 发表于 2013-1-5 23:41
调整gamma应该调整的是calibration cure对吧？这个显示器gamma如果和标准的2.2差距很大，会有什么结果？颜色怎么偏呢？

myliyifei 发表于 2013-1-11 23:07
据我所掌握的资料，基于CCFL和白光LED的LCD显示器，对比度都是固定的吧，能调节的只有背光亮度。我现在的问题不是要知道gamma是多少，而是说为了尽可能接近SRGB的标准，应该设置为多少

編老 发表于 2013-1-11 04:45
你的液晶显示器不够专业，好的液晶显示器非常的亮，眼睛几乎没法儿看，就像一大块白色平板光源！
只有亮度调整（实际上就是对比度），只需稍微调一点就行了（大致的粗调）
然后通过软件可以细调，有对比度和亮度控制，完全与CRT一样，对比度能够黑下来。至于Gamma可以用专门的测试图来决定。

研茗耘影 发表于 2013-1-9 13:55
校正后的……

Aphrodite 发表于 2013-1-5 11:24
Setting the gamma to the reported value can then help to reduce calibration artifacts like banding, because the adjustments needed for the video card's gamma table should not be as strong as if a gamma further away from the display's native response was chosen.

关于Gamma的设置，这句话才是关键，因为使用dispcalgui来校准其实是在调整显卡的Gamma，此时如果选择的Gamma值与显示器本身的曲线差距很大 ，则很容易出现所谓的Banding，就是在某些色彩上出现不均匀的色带，这在Photoshop里做一个彩色渐变可以很直观的看出来。此时你需要自己平衡你追求的是准确的色彩映射还是平滑的色彩过渡？

顺便说一句，只有专业的显示器才能调整显示器本身的曲线，这与我们平时调整显卡曲线的概念是完全不同的，得到的效果差距也很大。

dual 发表于 2013-1-5 12:29
看，反而手忙脚乱

http://zh.※※※※※※※※※.org/wiki/SRGB%E8%89%B2%E5%BD%A9%E7%A9%BA%E9%97%B4

http://www.argyllcms.com/doc/gamma.html

Also note that many color spaces are encoded with, and labelled as having a gamma of approximately 2.2 (ie. sRGB, REC 709, SMPTE 240M, Macintosh OS X 10.6), but are actually intended to be displayed on a display with a typical CRT gamma of 2.4 viewed in a darkened environment.
This is because this 2.2 gamma is a source gamma encoding in bright viewing conditions such as a television studio, while typical display viewing conditions are quite dark by comparison, and a contrast expansion of (approx.) gamma 1.1 is desirable to make the images look as intended.
So if you are displaying images encoded to the sRGB standard, or displaying video through the calibration, just setting the gamma curve to sRGB or REC 709 (respectively) is probably not what you want! What you probably want to do, is to set the gamma curve to about gamma 2.4, so that the contrast range is expanded appropriately, or alternatively use sRGB or REC 709 or a gamma of 2.2 but also specify the actual ambient viewing conditions via a light level in Lux, so that an appropriate contrast enhancement can be made during calibration. If your instrument is capable of measuring ambient light levels, then you can do so.
(For in-depth technical information about sRGB, see “A Standard Default Color Space for the Internet: sRGB” at the ICC website for details of how it is intended to be used)

If you're wondering what gamma value you should use, you can run “Report on uncalibrated display device” from the “Tools” menu to measure the approximated overall gamma among other info. Setting the gamma to the reported value can then help to reduce calibration artifacts like banding, because the adjustments needed for the video card's gamma table should not be as strong as if a gamma further away from the display's native response was chosen.

Real displays do not have a zero black response, while all the target response curves do, so this has to be allowed for in some way.

The default way of handling this (equivalent to 100% black output offset) is to allow for this at the output of the ideal response curve, by offsetting and scaling the output values. This defined a curve that will match the responses that many other systems provide and may be a better match to the natural response of the display, but will give a less visually even response from black.

The other alternative is to offset and scale the input values into the ideal response curve so that zero input gives the actual non-zero display response. This ensures the most visually even progression from display minimum, but might be hard to achieve since it is different to the natural response of a display.

A subtlety is to provide a split between how much of the offset is accounted for as input to the ideal response curve, and how much is accounted for at the output, where the degree is 0.0 accounts for it all as input offset, and 100% accounts for all of it as output offset.

Normally, profiles created by dispcalGUI only incorporate the colorimetric rendering intent, which means colors outside the display's gamut will be clipped to the next in-gamut color. LUT-type profiles can also have gamut mapping by implementing perceptual and/or saturation rendering intents. You can choose if and which of those you want after clicking “Advanced...”, by specifying a source profile and marking the appropriate checkboxes. Note that a input, output, display or device colororspace profile should be specified as source, not a non-device colorspace, device link, abstract or named color profile. You can also choose viewing conditions which describe the intended use of both the source and the display profile that is to be generated. An appropriate source viewing condition is chosen automatically based on the source profile type.

For more information on why a source gamut is needed, see “About ICC profiles and Gamut Mapping” in the Argyll CMS documentation.

One strategy for getting the best perceptual results with display profiles is as follows: Select a CMYK profile as source for gamut mapping. Then, when converting from another RGB profile to the display profile, use relative colorimetric intent, and if converting from a CMYK profile, use the perceptual intent.
Another approach which especially helps limited-gamut displays is to choose one of the larger (gamut-wise) source profiles you usually work with for gamut mapping, and then always use perceptual intent when converting to the display profile.

nother approach which especially helps limited-gamut displays is to choose one of the larger (gamut-wise) source profiles you usually work with for gamut mapping

Please note that not all applications support setting a rendering intent for display profiles and might default to colorimetric (e.g. Photoshop normally uses relative colorimetric with black point compensation, but can use different intents via custom soft proofing settings).