Non-photo blue (or non-repro blue) is a common tool in the

graphic design Graphic design is a profession, academic discipline and applied art whose activity consists in projecting visual communications intended to transmit specific messages to social groups, with specific objectives. Graphic design is an interdiscipli ...

and print

industry Industry may refer to: Economics * Industry (economics), a generally categorized branch of economic activity * Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery * The wider industrial sector ...

, being a particular shade of

blue Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when obs ...

that cannot be detected by graphic arts camera

film A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmosphere ...

. This allows layout editors to write notes to the printer on the print flat (the image that is to be photographed and sent to print) which will not show in the final form. It also allows artists to lay down sketch lines without the need to erase after

inking Inking may refer to: *Inking (attack), act of throwing ink on other person *Inking, a defensive activity of certain cephalopods and sea hares * Inking (comic book production) *Pen computing Pen computing refers to any computer user-interface using ...

Change in function

More recently, with digital scanning and image manipulation, non-photo blue fulfills its function in a different way. The artist can do their sketch and inking in the traditional manner and scan the page. Most scanners ''will'' detect the light blue lines. However, shifting to

greyscale In digital photography, computer-generated imagery, and colorimetry, a grayscale image is one in which the value of each pixel is a single sample representing only an ''amount'' of light; that is, it carries only intensity information. Graysca ...

and increasing the contrast and

brightness Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, ...

of the scanned image causes the blue to disappear. Another common approach involves replacing the blue

channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austral ...

with another channel – typically the red channel. The exact processes may differ depending on the scanner, settings and image-editing software, but the concept remains the same.

Black ink

The difference between the non-photo blue and black ink is great enough that digital image manipulation can separate the two easily. If a black-and-white

bitmap In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array A bit array (also known as bitmask, bit map, bit set, bit string, or bit vector) is an array data structure that c ...

setting is scanned in, the exposure or threshold number can be set high enough to detect the black ink or dark images being scanned, but low enough to leave out the non-photo blue. On a threshold scale of 0–255, this number would be approximately 140. Only with a considerably low threshold setting will the blue be detected; this however may greatly distort black lines and add a lot of

noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...

and black speckles, making the image potentially almost unrecognizable. Scanning in black-and-white makes it possible for the non-photo blue still to serve its original purpose, as notes and rough sketching lines can be placed throughout the image being scanned and remain undetected by the scan head.

References

{{DEFAULTSORT:Non-Photo Blue Printing terminology Shades of blue

Change in function

Black ink

See also

References