Reproducing pictures

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.