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ANNEX 3: CROSS REFERENCE OF COLOR SHIFT & COLOR MODELS
各 類輸出色彩偏差參考數據表及常用色 彩模式簡介
- last updated on Aug. 10, 2005 -

Index
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3.1 CROSS REFERENCE OF COLOR SHIFT 各類輸出色彩偏差
The following figures are only estimations based on empirical experience instead of any well-established industrial standard. There is no warranty of any kind, either express or implied, regarding the accuracy, reliability or correctness of the data listed below. Nevertheless, they may be regarded as a reference of our commitment in printing service to our customers.

Presumption:

  1. For those artworks presented in the form of soft copy, it is supposed that they are ripped by the same software/hardware rip without changing the color mode in different batch print jobs. 
  2. For those artworks presented in the form of film/hard copy, it is supposed that the same printing machines, ink and media are used in different batch print jobs. 
  3. The final printout should be viewed under the same lamination condition..
  4. CMYK color model, except for monitors and silk screen printing, is employed and the panetone processing color guide or equivalent serves as a common reference of standard.
- last updated on Aug. 10, 2005



VGA/XGA CRT Monitor
(RGB)
720dpi or lower Inkjet Printer
(CMYK)
Dye-sub Proof,
1440dpi+ Inkjet Printer
(CMYK)
1200dpi Color Laser  Proof
(CMYK)
CMYK film Press Proof
(CMYK)
CMYK offset printing (CMYK) Bromide Foto Paper,
Lambda
(CMYK/RGB)
Silk-screen Printing (Solid Color)
VGA/XGA CRT Monitor (RGB) +/- 5%






720dpi or lower Inkjet Printer
+/- 5% +/- 20% +/- 20% +/- 20% +/- 20% +/- 20% +/- 20%
Dye-sub Proof/
1440dpi+ Inkjet Printer


+/- 5% +/- 10% +/- 10% +/- 10% +/- 15% +/- 15%
1200 dpi Color Laser  Proof


+/- 10% +/- 10% +/- 10% +/- 15% +/- 15%
CMYK film Press Proof



+/- 5% +/- 5% +/- 15% +/- 15%
CMYK offset printing




+/- 5% +/- 15% +/- 15%
Bromide Foto Paper, Lambda






+/- 10% +/- 15%
Silk-screen Printing






+/- 10%


3.2 COLOR MODELS 色彩模式
3.2.1 Color Gamuts: By definition, color gamuts means the scope of color which can be reproduced using a certain output technology. As naked human eye is sensitive to 3 primary visible lights, namely Red, Green And Blue, output devices using RGB model is capable of displaying the greatest extent of color. However, it is applicable to light emitting devices like TV sets or Monitors only.
color gamuts
Click the image for larger image

The common printing methods using CMYK color model reproduces colors by screening the light reflected from either the base on which the colors are printed or the pigment of color itself. The color gamuts is smaller than RGB model due to the loss and distortion in the process of reflection and filtration except for some PMS colors which can reflect a special section of the color spectrum that even goes beyond the color gamuts of RGB model.  The following diagram shows how color image is reproduce using CMYK color separation method:

3.2.1.1 RGB Color Model:

RGB Model
Click the above image for more color swatch with illustration of color models in PDF format.

3.2.1.2 CMYK Color Model (Subtractive Color):

3.2.1.2.1 Working Principle of CMYK Color Model  工作原理:
Printed matter cannot emit light; it reflect light from luminous light source only.  A traditional painter may apply different colors on his palette to his canvas or paper with paint brush. Nevertheless, printing too many colors on media is not feasible from both the economic and  technical point of view. The current CMYK printing method use subtractive color. All colors are reproduced by screening the light (supposed to be white) reflected from either the base on which the colors are printed. The Color pigment of the 4 process color, C,M,Y and K work as filter which "subtract" one primary color from the white light respectively. The following diagram illustrates how the system works.  Overlapping different color ink may screen away unwanted primary color from the reflected light. This method only reproduced a smaller color gamuts compared with RGB or PMS color model.


cmyk model
Click the above image for more color swatch with illustration of color models in PDF format.





printing_lpi_illustration_web.jpg  


3.2.1.3 HSB Color Model:
This model defines color by "Hue", "Saturation" and "Brightness".

Hue represented by the relative location of  in the color wheel. For instance, if zero degree represent "Red", Magenta, Blue, Cyan, Green and Yellow are 60, 120, 180, 240, 300 respectively. Changing the Hue means shifting the color round the color wheel.

The second property of color is saturation which refers to the intensity of color. It ranges from 0 (i.e. gray) to 255 (i.e. fully saturated color).

The third property is brightness which represent the lightness or darkness of a color. As illustrated in a 3-dimensional model as shown in the diagram, the changes of the three properties of color are visualized by a column of color wheels. This color model is useful in tunning color temperature and brightness especially on TV or monitor.
hsb model
Click the image for larger image

3.1.2.4 PMS Color Model:
Sometimes the CMYK process colors cannot match a specific color for demanding print job. Spot color will be used. The most renowned spot color system is Pantone Matching System (PMS), which is a trademark system of over thousand colors identified by a unique color code. Every color is a premixed ink according to the formula provided by the vendor of PMS.

digital_image/pantone_DSCN8666web.jpg

PMS  is also commonly used in screen printing  or transfer printing because the halftoning approach for offset printing is not possible for this printing technology except some advanced equipment like those used for printing label directly on CD or DVD surface. 

3.2.2 Color Models and Conversion
彩色模式之轉換:
In the absence of a common algorithm for the conversion of different color models, all digital artworks created for printing purpose should be converted into CMYK model before they are sent to output devices. A significant range of RGB colors are not printable as they go beyond the color gamuts of CMYK or PMS color model. If not otherwise specified, the conversion will be done using the software of "Adobe" including "Illustrator" or "Photoshop".  It should be noted that different vendors have their own conversion algorithm in converting non -cmyk colors into cmyk colors but none can be claimed the universal standard.

3.2.3 Color Depth and Output Resolution 
The depth of color refers to the number of distinguishable colors that can be reproduced. The higher the resolution of output device, the more colors it can produce and so does the accuracy of the color with respect to the original artwork. A reasonable color shift should be acceptable and is not liable to any claim for non standard goods. Please refer to 
annex 5 for more information.


3.3 Color Swatch
色標
Some prominent printing solution vendor publish a series of color swatches as a standard reference guide for the printing industry. The most famous brand name product is the "Pantone" color guide series. However, our practical experience told us that even an artwork created in CMYK model could not be reproduced identically using different output devices. Unlike image setters, the current printers available in market manufactured by different  producer always print the color copy with their own emphasis or preference. It is always a disaster when using this hardcopy of artwork as a proof and quality control standard for the final product. To assist people in need of an impression about the discrepancy of color reproduction between their printing device and the standard color swatch, we created a "CMYK Electronic Color Swatch" in PDF format and post it on our web-site for all interested persons to download free of any charges. You may right click your mouse on the following image and save link target to your harddisk to get a free softcopy of "CMYK Electronic Color Swatch". Print the swatch using your own printing device and compare them to the standard color guide like Pantone Processing Color Guide".  Then you will have an idea about how far your printing device deviate from the offset printing machine.

images/color/cmyk_color_swatch.jpg

Click the above image for more color swatch with illustration of color models in PDF format.

Note: All the brandnames mentioned above belong to their respective owners.

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What's New? 最新情報

Our Committment to Creativity 我們對創新的理念

av_clip/creation_icon.gifFor more than two decades,  we've been working hard to achieve the seamless fusion of  old with new, east with west  and art with science. Neither a clumsy mixture nor  a simple crossover can satisfy us.  We've never thought that we 've really made it.  Yet we've tried our best to approach it without regret.

In this approximately 36sec promotion  trailer in  mpg-1 file of 4.3MB,  we not only show our committment to creative industry (Quicktime needed)., but also demonstrate a low cost production of mutimedia ad on the internet is simple and possible. More samples are available. Just click and check. 

在20年的歲月裡,我們曾努力不 懈地嘗試,揉合現代和傳統、東方和西方、藝 術和科技,我們不敢奢言成功、或滿足於簡單 的混合、以至笨拙的結合,但卻無悔追 尋這36秒的動畫, 表達我們對創作的理念, 也展示低成本創作之可能. 網頁內有更多我們的創作樣本.


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