progressive proofs (progs)

Set of proofs made during the four-color printing process; also called color proofs. Typically, there are seven different impressions in a set of progressive proofs: one for each color alone and then the combinations as succeeding colors are added. The final proof will show the finished color reproduction. An example of a progressive sequence follows: (1) impression of the red plate; (2) impression of the yellow plate; (3) impression of the yellow plate on the red plate; (4) impression of the blue plate; (5) impression of the blue plate on the yellow and red plate; (6) impression of the black plate; (7) impression of the black plate on the yellow, red, and blue plate. The progs serve as a guide and are used by the printer to match up inks in the four-color printing process. They also permit the customer to make any changes or corrections the need for which may become apparent as a result of the process.

Color Seperation

Definition: On a printing press each color of ink used in a document is printed one at a time. Each printing plate used on the press is made up only of components of the page that have that one color.

Separations are artwork split into component plates of cyan, magenta, yellow, and black in preparation for process printing (CMYK) or into the required number of plates for spot color printing. Each separation prints a single process or spot color. Digital files can be composite separations (all information in one file) or preseparated (each color on its own page).

During prepress you should print separations to your desktop printer to insure they will separate properly once sent to your commercial printer.

Scanners - the Process

• Flatbed scanners, also called desktop scanners, are the most versatile and commonly used scanners. In fact, this article will focus on the technology as it relates to flatbed scanners.
• Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer.
• Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text.
• Drum scanners are used by the publishing industry to capture incredibly detailed images. They use a technology called a photomultiplier tube (PMT). In PMT, the document to be scanned is mounted on a glass cylinder. At the center of the cylinder is a sensor that splits light bounced from the document into three beams. Each beam is sent through a color filter into a photomultiplier tube where the light is changed into an electrical signal.

Parts of a typical flatbed scanner include:

• Charge-coupled device (CCD) array
• Mirrors
• Scan head
• Glass plate
• Lamp
• Lens
• Cover
• Filters
• Stepper motor
• Stabilizer bar
• Belt
• Power supply
• Interface port(s)
• Control circuitry

The Scanning Process

Here are the steps that a scanner goes through when it scans a document:

• The document is placed on the glass plate and the cover is closed. The inside of the cover in most scanners is flat white, although a few are black. The cover provides a uniform background that the scanner software can use as a reference point for determining the size of the document being scanned. Most flatbed scanners allow the cover to be removed for scanning a bulky object, such as a page in a thick book.

In the image above, you can see the fluorescent lamp on top of the scan head.

• A lamp is used to illuminate the document. The lamp in newer scanners is either a cold cathode fluorescent lamp (CCFL) or a xenon lamp, while older scanners may have a standard fluorescent lamp.

• The entire mechanism (mirrors, lens, filter and CCD array) make up the scan head. The scan head is moved slowly across the document by a belt that is attached to a stepper motor. The scan head is attached to a stabilizer bar to ensure that there is no wobble or deviation in the pass. Pass means that the scan head has completed a single complete scan of the document.

The stabilizer bar is very durable and tightly secured to the body of the scanner.

• The image of the document is reflected by an angled mirror to another mirror. In some scanners, there are only two mirrors while others use a three mirror approach. Each mirror is slightly curved to focus the image it reflects onto a smaller surface.

• The last mirror reflects the image onto a lens. The lens focuses the image through a filter on the CCD array.

Look carefully at the image above and you can see all three of the mirrors plus the lens assembly in this scan head.

The filter and lens arrangement vary based on the scanner. Some scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image.

Click on the green Scan button to see the scanning process.

Most scanners today use the single pass method. The lens splits the image into three smaller versions of the original. Each smaller version passes through a color filter (either red, green or blue) onto a discrete section of the CCD array. The scanner combines the data from the three parts of the CCD array into a single full-color image.

Another imaging array technology that has become popular in inexpensive flatbed scanners is contact image sensor (CIS). CIS replaces the CCD array, mirrors, filters, lamp and lens with rows of red, green and blue light emitting diodes. image sensor mechanism, consisting of 300 to 600 sensors spanning the width of the scan area, is placed very close to the glass plate that the document rests upon. When the image is scanned, the LEDs combine to provide white light. The illuminated image is then captured by the row of sensors. CIS scanners are cheaper, lighter and thinner, but do not provide the same level of quality and resolution found in most CCD scanners.

We will take a look at what happens between the computer and scanner, but first let's talk about resolution.

Hues, Tints, Shades, and Saturation Colors

There are more colors that we can see and create than just Red, Green, Blue, Cyan, Yellow, and Magenta. Although we often depict the color wheel as shown above — with blocks of solid color. It is really millions of colors that blend one into another as we move around the wheel. Similar to this color wheel:

Each of those individual colors is a hue. Red is a hue. Blue is a hue. Purple is a hue.

You can change the saturation of a hue by adding black (shadow) or white (light). The amount of saturation gives us our shades and tints.

Add varying amounts of black to get shades. Think of the coming darkness and the darkening shadows to remember that a hue plus black equals a shade.

Add varying amounts of white to lighten a hue. The light hues are tints.

RGB and CMYK

Working with images destined for the screen or the Web, we designate colors by the amount of RED, GREEN, or BLUE in the color. In your graphics software these numbers might look like this:

A number between 1-255 designates the amount of each color RED, GREEN, or BLUE.

In order for your computer to understand these numbers we translate them into 6 digit hexidecimal numbers or triplets.

255 RED 255 GREEN 0 BLUE becomes FFFF00. The first pair (FF) is the Red, The second pair (FF) is the Green, and 00 is the Blue. FF is the hexidecimal equivalent of 255 and 00 is the hexidecimal equivalent of 0.

In print, we try to reproduce the colors we see. Remember how color (light) is made by subtracting differing amounts of other colors from the additive primaries (RGB)? Well, in printing when we are mixing (adding) inks together the colors don't come out as we might expect.

Therefore, we start with the subtractive primaries (CYM) and mix those in varying amounts (plus BLACK abbreviated as K) to get the colors we see printed in magazines and books.

Colors are mixed in percentages such as:

50% CYAN 100% YELLOW 25% MAGENTA

This CMY(K) color model is only one of many ways we can express color for print — but we'll save that topic for another feature.

There are other color-related terms which we'll address briefly. The overview on the next page will help you see how the different terms work together and interact to describe the colors we see in the world, in print, and on the Web.

Color Basics for Print Work

Did you know that the color wheel you learned in school isn't the same as the colors used for the Web? It's not even the way colors are mixed for printing? Well, ok, same colors, just different arrangements and mixes.

• The traditional primary colors are RED, YELLOW, and BLUE.

• Mix two primary colors to get the complementary colors.

• The traditional complementary colors are ORANGE (Red plus Yellow), GREEN (Yellow plus Blue), and PURPLE (Blue plus Red).

In grade school you probably had plenty of opportunities to mix primary colors and make new colors. It was magic!

The way we see color is a bit different. You've probably seen a prism break a beam of light into a rainbow of colors. The visible spectrum of light breaks down into three color regions: RED, GREEN, and BLUE.

• Add RED, GREEN, and BLUE (RGB) light to create WHITE light. Because you ADD the colors together to get White, we call these the additive primaries.

• Subtract one of the colors from the other three and you are left with yet another color. RGB minus RED leaves CYAN. RGB minus the BLUE leaves YELLOW. RGB minus GREEN leaves MAGENTA. These are called the subtractive primaries (CMY).

Try mixing GREEN and BLUE paint and I bet you don't end up with a nice CYAN. Why? Because the color we see is reflected light and light and ink don't work in quite the same way.

Now put all this aside for a bit and look at the way we try to reproduce color in print and on the Web.

Screen Printing

Silk-screening is the process used to produce most t-shirts. It is much easier to explain the process using pictures. Take a look at the pictures below; Package #1 is used to produce the t-shirts in these pictures. After you are done looking at the pictures and learning a little more about silk-screening, take a look at the rest of the site.

setting up the printer

adjusting the screen so the image is where you want it

registration brackets and me smiling :)

placing the ink in the screen and removing the screen

spraying textile adhesive on the t-shirt platton and placing a test pellon on the t-shirt platon

spreading the ink over the screen to print an image

It is hard to see that there is a test pellon down on the board. I placed the pellon under the flash dryer to cure it ( Flash dryer is the red box with a wood handle it heats up to 350 degrees to completely dry and cure the ink so it won't wash off _ it take about 1 minute to cure the ink )

Placing a t-shirt on the platton, taking the test pellon off because it is done

placing the screen on the t-shirt to print it

the registartion brackets keep the screen in place while you are printing also if you print more than one color they keep all the colors locked in the position you set them at

after printing I placed the t-shirt on the second board ( drying board ) to cure it under the flash dryer

While the first t-shirt is drying I can print another one. You can print a one color print every minute

Here the first t-shirt is dry and I'm removing it and placing the second one under the flash dryer

and here the second shirt goes under the dryer so I can print the third

and so on and so on :)

Step by step how to silkscreen

To begin you print out a film positive (clear or velum) on your desktop printer (laser is best but inkjet will work) on the right photo I'm pointing at a target ,this is needed in order to register your print if you have more than one color to put on a t-shirt. note ; the photo on the right is transparent velum this is important to understand ,light must be able to pass through the paper in order to make a silkscreen. Also art work should be left up to the professional when it comes to a multi color print we have artists available for you to use at a nominal fee, they will give you the film positives that are needed so you can do a professional job for your customers .

In order to print this three color logo I had an artist make three film positives one positive for each color ( see below )

Each positive has targets (registration marks) on each corner. Over time you can learn how to do color separation yourself (most screen printers use a program called Corel Draw) but as I said before it is better to have someone familiar do this until you get the hang of it.