General Introduction Of Soft Proofing & Colour Proofing with WiT Lamp

Dr. Chris Bai - Senior Colour Expert and the manager of the Colour Technology Lab at BenQ

2021/09/24

It is no exaggeration to say that the last step of our photography activity is on the satisfaction of printing and being able to share the printed photos. But we often feel disappointed that the colour of the print out does not exactly match the original image.

The current LCD monitors are displaying the colours under the RGB colour model. But our printers we are working with use the CMYK colour model.

Additive Colour

RGB Colour Model

Additive colour theory states that colours are produced by mixing light, specifically red, green and blue light. These three colours are called the primary colours for additive colour model. Other colours can be produced by mixing various amounts of red, green and blue light to create secondary colours: cyan, magenta, and yellow. Mixing red and green light gives you yellow light. The overlap of green and blue produces cyan. By combining blue light and red light, magenta is produced. When all three primary colours are added together, white light is created.

The commonly used RGB colour space uses the additive colour model where red, green and blue light are mixed in various amounts to create a broad range of colours.

Subtractive Colour

CMYK Colour Model

In the subtractive colour system, colours are produced by mixing colorants. Certain colour of light are absorbed (subtracted) by the colourants whereas others are reflected and seen by the viewer. The subtractive primary colour are cyan (C), magenta (M), and yellow (Y). If we mixed yellow and cyan, we would get green; mixing yellow and magenta gives us red; and combining magenta and cyan produces blue. Theoretically, the combination of all three primary colours would give us black; however, in reality, a dark brown results. Hence, a fourth colour, black (K), is added to colour printing to compensate for the imperfect colour produced from the primary colour trio.

This subtractive color model is referred as the CMYK color space comprising of cyan (C), magenta (M), yellow (Y) and black (K).

In this knowledge content, we want to share how to minimise the gap of the colour differences between the original images and print outs. Furthermore, let's study together on how we can double-check and determine the colour accuracy of the printed photos.

Photo Printing with ICC profile - Soft Proofing

What is a ICC profile for a print & paper?

Print profiles are files that determine how colors are printed with a specific printer and paper. Combined with our print profile software, this transforms the image from the color space (range of colors) to the color space for the printer and paper. The printer will make a colour from the combination of the CMYK. The profile will control the printer that yellow has to be this much yellowish and blue has to be this much bluish. Also, the print profile is sharing the colour space information to the printer.

To create a print profile for colour critical work, we need to print out the colour chart first by the paper which we want to print out. As same as monitor calibration, we read all colours with a calibrator. The printer profile's colour accuracy depends on how many patches you will load. We recommend you to load over 1000(???) patch loads to secure minimum accural colour.

But the colour chart loading is not that easy and really a time-consuming job. Therefore, you can use a ICC profile from a printer vendor or paper vendor if you are not a professional level.

Download Epson paper's ICC profile

Download Kodak paper's ICC profile

Download Canon printer's ICC profile

< SOP > Soft Proofing setting in the Photoshop

Colour Proofing Light

Brightness & Colour Temperature Of The Light

Now we finished what we can do when we print photos. let's check image colour with the calibrated BenQ SW monitors. Let me ask some questions. Where are you looking at the photo? is there any lighting lamp on your desk? Or what is the colour tone of your lighting? if you are checking under sunlight, is it sunset time or morning without cloudy? Right, there is another checkpoint about the lighting when you are checking the photo. Warm tone light will shift your photo's colour to reddish. Cool tone light will shift your photo to bluish. as you can see from the below right side photo, depends on the weather and daylight's time, colours are reflecting different colours.

Let’s take a look at the four photos shown above right. Each of the photos is shown on four different screen monitors. Note how different the colours look on the monitors. Before colour management is implemented on the four devices, there are visible colour differences due to varying hardware technologies and colour settings. The default colour settings, for example, colour temperature, saturation and contrast, you find on your home’s display will generally cater to the colour needs of typical use. However, for commercial printing companies and for freelancers and professionals whose work requires colour precision, colour management becomes essential in their workflow.

LCD monitors of the same model will also exhibit colour mismatch due to deviations in backlight modules and colour filters. Calibration can reduce the colour differences between displays.

Below are devices that use different colour systems to produce colour. Optical devices use additive colour mixing while print devices use subtractive colour mixing.

1.Optical input devices: cameras, scanners

2.Optical output devices: monitor displays, projectors

3.Print device: printers

Due to those reasons printing industries are using standard lighting equipment to check the colour proofing.

<SOP> How to set WiT to D50 or D65 for the colour proofing

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