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lab color

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lab color

文章發表人 DonDon 發表於 2007-08-14, 16:59

有無大大知有咩好? 同埋常唔常用? :sorry: :sorry:
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DonDon
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2006-01-26, 14:19

文章發表人 peterso 發表於 2007-08-14, 17:01

:hypno: :hypno: :hypno: :hypno: :hypno:
圖檔圖檔圖檔
圖檔圖檔圖檔
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2004-11-16, 18:33

文章發表人 yukyuk909 發表於 2007-08-14, 17:02

喔...去左聽野??? :question2: :question2:
唔多常用por~~~
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2007-06-05, 10:40

Re: lab color

文章發表人 射擊人 發表於 2007-08-14, 17:07

DonDon 寫:有無大大知有咩好? 同埋常唔常用? :sorry: :sorry:


其實好有用... :010: :010: :010:

不過我唔會講出泥o既~ :showtongue: :showtongue: :showtongue:
射擊人
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2004-11-16, 16:46

文章發表人 soda 發表於 2007-08-14, 17:13

我都有用開,
不過你請我食飯先教你 :drink1: :004:
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2006-06-29, 13:42

Re: lab color

文章發表人 yukyuk909 發表於 2007-08-14, 17:14

係咪一個總一各硬件color o既...準則黎呢???
:a013: :a013: :a013:
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Re: lab color

文章發表人 DonDon 發表於 2007-08-14, 17:38

射擊人 寫:
DonDon 寫:有無大大知有咩好? 同埋常唔常用? :sorry: :sorry:


其實好有用... :010: :010: :010:

不過我唔會講出泥o既~ :showtongue: :showtongue: :showtongue:


唔6就唔6啦! ban :007: yeh! :notinterest:
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DonDon
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文章發表人 DonDon 發表於 2007-08-14, 17:38

soda 寫:我都有用開,
不過你請我食飯先教你 :drink1: :004:


:angry: :angry: :angry:
圖檔
DonDon
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文章發表人 postmaster 發表於 2007-08-14, 17:42

中國人腐敗思想 :showtongue: ; 教識無師父
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2005-07-16, 14:51

文章發表人 debug 發表於 2007-08-14, 18:18

http://en.wikipedia.org/wiki/Lab_color_space

Advantages of Lab

Unlike the RGB and CMYK color models, Lab color is designed to approximate human vision. It aspires to perceptual uniformity, and its L component closely matches human perception of lightness. It can thus be used to make accurate color balance corrections by modifying output curves in the a and b components, or to adjust the lightness contrast using the L component. These transformations are difficult or impossible in the RGB or CYMK spaces, which model the output of physical devices, rather than human visual perception.

Because Lab space is much larger than the gamut of computer displays, printers, or even human vision, a bitmap image represented as Lab requires more data per pixel to obtain the same precision as an RGB or CMYK bitmap. In the 1990s, when computer hardware and software was mostly limited to storing and manipulating 8 bit/channel bitmaps, converting an RGB image to Lab and back was a lossy operation. With 16 bit/channel support now common, this is no longer such a problem.

Additionally, many of the “colors” within Lab space fall outside the gamut of human vision, and are therefore purely imaginary; these “colors” cannot be reproduced in the physical world. Though color management software, such as that built in to image editing applications, will pick the closest in-gamut approximation, changing lightness, colorfulness, and sometimes hue in the process, author Dan Margulis claims that this access to imaginary colors is useful going between several steps in the manipulation of a picture.[6]

debug
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2004-11-19, 22:53

文章發表人 射擊人 發表於 2007-08-14, 18:40

debug 寫:http://en.wikipedia.org/wiki/Lab_color_space

Advantages of Lab

Unlike the RGB and CMYK color models, Lab color is designed to approximate human vision. It aspires to perceptual uniformity, and its L component closely matches human perception of lightness. It can thus be used to make accurate color balance corrections by modifying output curves in the a and b components, or to adjust the lightness contrast using the L component. These transformations are difficult or impossible in the RGB or CYMK spaces, which model the output of physical devices, rather than human visual perception.

Because Lab space is much larger than the gamut of computer displays, printers, or even human vision, a bitmap image represented as Lab requires more data per pixel to obtain the same precision as an RGB or CMYK bitmap. In the 1990s, when computer hardware and software was mostly limited to storing and manipulating 8 bit/channel bitmaps, converting an RGB image to Lab and back was a lossy operation. With 16 bit/channel support now common, this is no longer such a problem.

Additionally, many of the “colors” within Lab space fall outside the gamut of human vision, and are therefore purely imaginary; these “colors” cannot be reproduced in the physical world. Though color management software, such as that built in to image editing applications, will pick the closest in-gamut approximation, changing lightness, colorfulness, and sometimes hue in the process, author Dan Margulis claims that this access to imaginary colors is useful going between several steps in the manipulation of a picture.[6]



a lot of theoretical info with nil practical info ~

DRY吹唔做~ 呃錢~ :whistling: :whistling: :whistling: :whistling:
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2004-11-16, 16:46

文章發表人 debug 發表於 2007-08-14, 18:43

射擊人 寫:
debug 寫:http://en.wikipedia.org/wiki/Lab_color_space

Advantages of Lab

Unlike the RGB and CMYK color models, Lab color is designed to approximate human vision. It aspires to perceptual uniformity, and its L component closely matches human perception of lightness. It can thus be used to make accurate color balance corrections by modifying output curves in the a and b components, or to adjust the lightness contrast using the L component. These transformations are difficult or impossible in the RGB or CYMK spaces, which model the output of physical devices, rather than human visual perception.

Because Lab space is much larger than the gamut of computer displays, printers, or even human vision, a bitmap image represented as Lab requires more data per pixel to obtain the same precision as an RGB or CMYK bitmap. In the 1990s, when computer hardware and software was mostly limited to storing and manipulating 8 bit/channel bitmaps, converting an RGB image to Lab and back was a lossy operation. With 16 bit/channel support now common, this is no longer such a problem.

Additionally, many of the “colors” within Lab space fall outside the gamut of human vision, and are therefore purely imaginary; these “colors” cannot be reproduced in the physical world. Though color management software, such as that built in to image editing applications, will pick the closest in-gamut approximation, changing lightness, colorfulness, and sometimes hue in the process, author Dan Margulis claims that this access to imaginary colors is useful going between several steps in the manipulation of a picture.[6]



a lot of theoretical info with nil practical info ~

DRY吹唔做~ 呃錢~ :whistling: :whistling: :whistling: :whistling:


Better than you! You haven't even said anything about lab color other than you wouldn't tell us :patpat1: :patpat1: :patpat1: :patpat1: :patpat1: :patpat1: :patpat1: :patpat1: :patpat1: :patpat1:
debug
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2004-11-19, 22:53

文章發表人 Diablo 發表於 2007-08-14, 21:36

http://dgrin.smugmug.com/gallery/1108502

This is a very good tutorial on the use of LAB colour. I found it extremely useful for enhancing dull landscape pics.

You can easily write a macro and apply the techniques.

There are also a lot of good PS tricks from the website, all free.

Enjoy!
Diablo
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註冊時間:
2004-12-13, 22:05

文章發表人 soda 發表於 2007-08-14, 22:20

Lab模式由三個通道组成,

L通道表示亮度,它控制图片的亮度和對比度
a通道包括的顏色從深綠(低亮度值)到灰色(中亮度值)到亮粉红色(高亮度值)
b通道包括的颜色從亮藍色(低亮度值)到灰色到黄色(高亮度值)。

Lab模式與RGB模式相似,色彩的混合將產生更亮的色彩。
只有亮度通道的值才影嚮色彩的明暗變化。可以將Lab模式看作是两個通道的RGB模式加一個亮度通道的模式。Lab模式是與設備無關的,可以用這一模式编辑處理任何一幅圖片(包括灰度圖片),並且與RGB模式同樣快,比CMYK模式則快好幾倍。

Lab模式可以保証在進行色彩模式轉換時,CMYK範圍内的色彩沒有損失。如果將RGB模式圖片轉換成CMYK模式時,在操作步驟上應加上一個中間步骤,即先轉換成Lab模式。在非彩色的排版過程中,應用Lab模式將圖片轉換成灰度圖是經常用到的。對於一些互聯網上下載的RGB模式的圖片,如果不用Lab模式過濾後再轉換成灰度圖,那應在排版軟件排版時,有時就無法對圖片進行排版。

在编輯處理圖片時,盡可能先用Lab模式或RGB模式,在不得已時才轉成CMYK模式。而一旦轉成CMYK模式圖片,就不要輕易再轉回來了,如果實在需要的話,就轉成Lab模式地圖片進行處理。如果用於掃描輸入的原圖片是彩色圖片,但該圖片是用於灰度版面中的,用掃描儀輸入圖片時,不要將原圖片直接輸入為灰度模式,應用RGB模式輸入圖片,用RGB模式處理好圖片後,將其先轉換為Lab模式的圖片,再通過通道分離命令,選取L通道的圖片作為印刷用灰度圖片。
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2006-06-29, 13:42

文章發表人 Jess 發表於 2007-08-14, 22:37

Soda好勁~

p.s. Jelly隔離果隻係??
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2005-01-10, 15:52

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