As the picture says, all great prints start with great color separations. There’s no getting around this. So read on and learn about the different ways we create color separations for the purpose of screen printing onto tee shirts.
The first step in creating great seps is choosing the process that will give you the best results for each individual image. The processes are:
Spot color separations
Spot color separations consist of solid color only. There are no gradations, only areas of solid color.
There are more detailed explanations than this but for a general overview, this should suffice. Keep it simple; spot color = solid color.
Spot color separations, the simplest of all processes, can be handled within Illustrator or Photoshop.
Simulated process separations
Simulated process (aka spot process) is the method most widely used to separate photorealistic images in order to be screen-printed.
The process relies on mixing colors in order to trick the eye into believing it sees more colors than are really there. For instance, a yellow can have a little bit of red on top of it in order to give the viewer the sense of seeing orange.
It is a common misconception that colors physically mix to produce a new color. As you can see from the image above, the colors do not mix at all but from a short distance, we still see the image as having orange.
The complexity of simulated process color separations can range from rather simple, as shown above, to fairly complex.
4-Color Process CMYK Color Separations
Four color process CMYK color separations is a borrowed tool from the offset printing world. It requires the use of 4 colors set at different angles from one another to create a Rosette pattern.
Four color process CMYK color separations, though not ideal for screen-printing, is commonly used to print complex images onto white and/or light-colored tees.
This reduces the number of screens needed, and therefore, production costs as well.
These seps were made automatically with RSG’s “Easy 4C” Photoshop scripts.
Index process color separations
Index process color separations are comprised of square “dots”. The result is “dithering”, a process in which an image is produced using a limited number of colors.
Like the earlier examples, this is also used to trick the eye into thinking it’s looking at more colors than it really is.
Though aged, index is still a relevant, though not terribly popular, choice when it comes to creating color separations. When printing index process color separations, it is common to print the darker inks first.
Creating color separations
The process of creating color separations for screen-printing is wide open. There is no one perfect methodology. However, there are a few things we can do to help the process before we start pulling color.
There is a difference between inspecting the image and inspecting the file. Although, these two steps are usually done at the same time.
Inspect the image
Take a look at the image and decide which method of separation would be best. Zoom in and see what the image looks like up close and personal.
As we’ve seen with the previous two images, things can look much different from afar than up close. Looking at an image up close will let you know what you’re in for before you start your separations.
Inspect the file
While looking the image and judging which process is best suited for it, take a look at how the file was built. Answer these important questions.
Find out if you can use the layers, paths, or existing channels to help segregate parts of the image in order to pull color more easily.
Make sure it’s at the final print size and at a proper resolution (200-300dpi). As simple as this sounds, you’ll kick yourself twice if you complete a sep only to realize the file is 72dpi and entirely too small to print.
Important: “Final art files” are sometimes different from the comp. As such, it is important to check the two against one another. I assure you, there will be times where this will bite you in the butt if you don’t make it a habit.
Ballpark your colors
At this point, it’s best to estimate the color count. Not only is this needed for press limitations, it will greatly impact how you approach the separations.
You may discover that the art needs to be changed at this point to accommodate your machine.
A tip for shop owners: complete these steps before giving a written quote. You can never truly know how many colors a job will require until you have taken a good look at the art.
Unwanted/unexpected art charges put a sour taste in most every customer’s mouth. It can put one in yours as well if you choose to eat the extra costs in order to keep your customer happy.
Should I sep in layers or channels?
We sep in channels, period. There is no reason to separate an image in layers. In fact, if you do, you’re committing one of the 7 mistakes rookie separators often make.
Methods of pulling color
The most popular is Select > Color Range, which every shop owner/separator should be familiar with. A good place to start is this how to separate grayscale images tutorial if you’re not up to speed.
Then there’s the HSB method. “HSB” stands for Hue, Saturation, and Brightness. This is a method of pulling color, just like Select > Color Range. This is not a process and shouldn’t be referred to as such.
Just as we wouldn’t call them “Color Range seps”, we don’t call them “HSB seps”. They are methods. These methods are used to produce simulated process color separations, aka spot process color separations.
Another method is to use the composite channels and manipulate the values. A common use of this is to make your underbase from the lightness channel of an image in the lab color mode.
To do this, duplicate your image and change the mode to lab color. Then drag the lightness channel into your working file. Change its color to white, label it “base” and you’ve got a good foundation for an underbase.
“Putting” color instead of pulling
One of the things I teach is to never let the computer run the show. This is a mistake people fall into when separating. When the computer won’t allow you to pull color from an area in any image…
…put it there.
Don’t be afraid to paint in color where color needs to go. The computer isn’t a screen-printer, you are. Don’t let it tell you where you’re going to put down color.
How to output color separations
To output color separations, I’ve always used Illustrator. This does not mean that all of my seps are built in Illustrator.
Build your simulated process color separations in Photoshop. Save the file as a DCS2.0, TIFF (8bits/pixel), Single file with color composite (72pixel/inch), ASCII85 encoding.
Place this DCS2.0 .EPS into an Illustrator template, which contains centerlines, registration marks, and color callout boxes. You can download that template here.
File > Print or Cmd+P to bring up the print dialog box.
From here, individual output requirements will vary. For those with a RIP, follow the instructions that came with the RIP system. This usually requires saving as a PS but as mentioned, this varies.
For those without a RIP but whom have a postscript capable printer, do the following in Illustrator’s print dialog.
Printing from Illustrator gives you the ability to output the entire job in one fell swoop. It also allows for output of vector elements so long as they do not touch any of the elements from the DCS .EPS. Legal lines with small text, sponsor logos, and students’ names are all good examples of this.
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