Reproducing pictures
Jan 14, 2015
Reproducing pictures
Fundamental:• Type consists of symbols derived from varying widths of lines. We communicate via type by
translating the symbols into language and meaning. This is linear communication.• Pictures are non-linear communication. We take in the image holistically, and translate it into
meaning by making comparisons with that which we recognize from our life experience.• Accurate reproduction of visual images (pictures) must involve varying shades, from light to
dark• However, in printing processes there is either ink, or no ink• No practical reproduction process is able to reproduce infinite shades from light to dark
Therefore• Any reproduction process using current technology must trick the eye into seeing
shades from dark (pure color or ink) to light (no color or ink)• Current technology utilizes screening, which breaks pure color into dots that
simulate shading
Tint blocks are used to simulate shades
from light to dark
The amount of shading is measured in percentages
of the pure color
100 % black 50% black 10% black
Drop-out
Or Reverse
You can place type within a tint block, but you must create contrast with the tint block. Doing this is called creating a drop-out or a reverse.
Overprint
Placing dark type over a light backgroundis called an overprint.
Overprint
Reverse
When working with overprints and reverses, contrast in color and hue is important. These examples fail in this:
Be wary of backgrounds
When working with overprints and reverses, be careful to use a neutral background. Failure to do so can have unfortunate results. This mistake is common in web pages.
An attempt to use a clever
background, with resulting loss of
contrast, legibility and readability
Gradients can backfire
A gradient is neither light nor dark,but a gradual transition from light to dark. Reverses or overprints in gradients will have bad results, if used carelessly.
Reproducing pictures
• You must use either the basic technology of contrast, or the technology that creates tint blocks.
• Images created from contrast are called line art. They are either simple outlines, with no shading, or they use lines in combination to reproduce shading.
• Etching is an example of this kind of picture reproduction. The illusion of shading is produced by many tiny lines.
Detail of an etching by Francisco
Goya entitled
“They say yes and
give their hand to the
first comer” (1797)
Continuous tone images• Images reproduced by using the technology that
creates tint blocks are called “continuous tone” images, because they have the illusion of continuous, unbroken shades from light to dark.
• To reproduce these images, the image must be broken into dots, a technology called the halftone process
• Any printed images will either be line art, or a halftone image. There is no other practical alternative in today’s printing technology.
Two ways to reproduce pictures
• High-contrast images are converted to line art• Continuous tone images must be translated into
halftones
Line Art
A halftone imageNote the dots. This example is a very low-density screen. Compare this to the screen used to make the tint blocks in the earlier slides.
Digital tools use a different method
• Electronic processes break the image into pixels (picture elements)• These create shades of gray on the monitor screen, or shades of colors• The clarity of the image, called resolution, is measured by pixels per inch (ppi).
The greater the ppi, the finer the resolution.• However, the greater the ppi, the more computing space needed to analyze the
image. • Typical web page images are 72 ppi; pictures meant to be reproduced as
printouts can be 200 or more ppi.
200 dpi, 800% enlargement
72 dpi, 800% enlargement
• If a screen image is printed, these pixels are in turn reproduced as dots in printouts. (Printer specifications will be in dots per inch, or dpi.)
• The greater the dpi, the finer the screen and the better the picture reproduction.