Paper plays a vital role in colour reproduction because its optical and surface properties impact how light is reflected and therefore how colour and tonal values appear when printed. Hence, it is necessary to know these factors and understand how paper can play a role on how colours are perceived by the human eye.
The type of paper on which colour is reproduced has a huge effect on the way the colour appears. The same colour when printed on a smooth coated paper is more reflective because light is not as diffused as it would be by the texture of a coarser uncoated paper. Gloss coatings enable more light to be reflected, which is attributed to making colours “pop”. This is especially helpful in making photos appear more colourful and saturated. Even different grades of coating (Cast Coated, Gloss, Silk, Dull, Matte) will affect how the same colour is perceived.
Paper Brightness and Whiteness
“White” paper comes in various shades of white from very bright cool white to softer, warmer pale ivory white. The brightness of a piece of paper is typically expressed on a scale of 1 to 100 with 100 being the brightest. Brightness is the volume of light reflected off the sheet of paper. General multipurpose bond paper has a paper brightness in the 80s. Photo papers are normally in the mid to high 90s.
Paper whiteness refers to the shade of the sheet of paper. The three major shades of paper are balanced white, warm white and blue white. Most coated papers and many uncoated papers are currently manufactured to a blue white shade because to the human eye, the blue white shade appears to be brighter. So if you take three sheets with different whiteness, the sheet with the blue white shade will appear to be the brightest even though all three sheets have the same brightness rating.
The brighter and whiter the paper, the more it reflects light, enabling the printed piece to achieve higher contrast as well as a wider gamut of colour.
The less bright and less white a paper is, the lower its ability to reflect light, and therefore the narrower the amount of contrast and colour that is possible in the printed product. This is sometimes a desirable effect as documents with more text and less photos would be better served by a paper that is more subdued, allowing the readers’ eyes to focus on blocks of type without being distracted by paper glare.
Printing on coloured paper or paper that is not white will adversely affect the colours. For example, a black ink can appear to contain colour (colour cast) when printed on a colour substrate.
Although not technically a paper issue, the viewing condition will also greatly affect how colours are perceived. Although the human eye makes certain colour compensation, viewing the same printed piece under bright daylight, shaded daylight, fluorescent lamps, incandescent “white” lamps, etc. would yield different results (also known as “metameric failure“). Also, bear in mind that if you’re looking at a proof or comparing the proof to a printed piece, you have to view it under the intended viewing conditions (typically D50 or D65). Pantone now sells Lighting Indicator stickers which makes it very easy to determine if your viewing conditions are ideal for accurate colour evaluation.
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