At TS Designs, your artwork will be screen printed – ink is placed in a fine mesh screen in the shape of your design and is squeegeed through the screen onto your t-shirt.
Most of the time, your design will be printed in spot colors – that means each color in your design gets printed individually through a separate screen, coming together to make your design when all is said and done. To learn more about how we print, check out our detailed article on how our own special flavor of screen printing works.
Spot color printing requires your artwork to be separated into spot channels so our art department can output the film positives used to then create the screens. Depending on how your artwork is set up, that can be very easy, or very time consuming. This guide will give you the tools you need to avoid costly art fees resulting from us having to separate your artwork for you.
The first thing you need to know is the difference between vector and raster files.
Raster (aka bitmap) images are created by defining the color of set points (aka pixels) across a rectangular grid. So, if you have a 1,000 pixel wide by 800 pixel tall graphic, each of the 800,000 pixels in that graphic are specifically defined in the file.
The example to the right shows a small smilie face blown up so you can see each individual pixel as it is defined (click the image to get a better look). In this case, each point is assigned a red (R), green (G), and blue (B) value, which determines how it appears on-screen.
One of the major hallmarks of a raster image is what happens when you try to zoom in. Since each pixel on the grid is defined as a specific color, there’s a limit to how big you can make the image before it “pixelates” – when the pixels are enlarged to the point that they become visible to the eye. Again, look to the zoomed in version of the smilie to see an example of pixelation.
The vast majority of images you see on the internet are raster images, and photographs are always raster. There are a gajillion different raster image formats. Some of the most common you’ll recognize are jpeg, png, gif, tiff, and psd. There are many raster editing programs out there as well, ranging from MS Paint to Photoshop – pretty much any photo editor is a raster editor.
Vector images use mathematical expressions to create points, lines, curves and other shapes, and are the format of choice for screen printers.
Instead of telling the computer to make point X blue and point Y green in a rectangular grid, a vector image tells the computer to draw a smooth line following a certain curve for a certain distance. Since the formulae used to create each element will essentially “recalculate” each element every time a new graphic size is set, vector graphics can be infinitely resized while maintaining the same image quality.
Vector graphics can only be made on a computer – photographs or scans of drawn artwork are always raster, and with rare exception, raster images cannot be converted to vector.
Common vector file formats are pdf, ai, eps, and svg. But just because a file is saved as a pdf doesn’t mean that it’s entirely vector art – raster elements can be embedded in a vector file and do not become vector as a result.
The Meaningful Difference
From our perspective, vector images are preferable to raster for two main reasons.
First off, vector images can be scaled to any size without causing quality issues like pixelation. The image on the right shows an example of what happens if you try to enlarge a specific part of a vector or raster (bitmap) image. Notice how the vector image remains crisp and clear while the raster image pixelates to the point of unreadability.
Ease of Separating to Spot Colors
Raster images are often hard to separate into spot colors. Even if they’re created on a computer, raster graphics do their best to blend colors together. Even if you create artwork in Photoshop at high resolution with solid colors, the program will make the individual pixels between two areas of color a blend of both shades. For an example, look at the bitmap magnification in the image to the right. See how the line of pixels between the black and white are gradients of gray?
Remember, we’re printing spot colors with each color in its own screen. We can’t print a tiny gray line between the solid black and white areas. And in a raster file, small gradients like that will be everywhere one color runs into another. As a result, our artists will have to spend time telling the computer which spot color to fill those areas in with so they can make separations before printing the film positives. That costs you money.
By comparison, vector images are easier to separate into spot colors. In fact, vector images are pretty much already separated into spot colors because each shape created in the program is filled with a single, solid shade with a stark border between that shape and any shape of a different color.
Look at the vector magnification to the right. See how the line between the white and black areas of the design is completely stark? There’s nothing but an area of black and an area of white, no color in between. Our artists can go directly to film without having to mess with the file.
Things to Look Out for with Your Artwork
If you’re a designer, or have access to one who can assess your art files, check out our Designer’s Guide to Print-Ready Art.
If not, here are some of the most important things you can look out for to ensure your design is printable.
More than 6 Colors
There’s a limit to how many screens we can load onto one of our presses. Since each spot color has to be printed through its own screen, that means there’s a limit to how many colors you can print in a single design. Try to keep yours at 6 or below – both because of our equipment limitations and because you have to pay more for each screen you use.
First off, we’d prefer vector art for reasons mentioned above. But if you have to send us raster files, at least avoid the biggest pitfall: low resolution. The best way to avoid this – DON’T just download an image off the internet for us to print. We’ll come back to that in a moment.
Low resolution artwork is the most common problem we run into. As mentioned before, raster images are just a rectangular grid of points, or pixels, that are set to be specific colors. Image resolution is essentially the amount of detail, or information, contained within a picture. It’s measured by how many pixels wide and how many pixels tall that image is. So if I have an image that’s 900px wide and 600px tall, it’s resolution is 900×600.
This matters because we want as much detail to print as possible, and a low resolution image doesn’t have that much detail.
So how low is too low? Ideally, we want 300DPI (dots per inch) for printing purposes. That means that for every 300 pixels, you get just one inch. So that 900×600 graphic you’ve got? You can only print it 3 inches wide by 2 inches tall.
Now back to why you shouldn’t download images off the internet to print. We want as much information in your artwork as possible so we have a lot of detail to work with. Conversely, images put on web pages are purposefully stripped of as much information as possible so that they will be a small filesize and load faster in your web browser. Google “image compression” and you’ll find literally millions of webpages discussing the best way to compress images to make them as absolutely tiny as possible to optimize your website.
Want an example? Check out the TS Designs logo at the top of this page. It’s resolution? 263×98. If you wanted to print that at 300DPI, it would have to be less than an inch wide.
So what about that 600×400 image that you just have to have printed at 10 inches wide? Well there are a couple things we can do. We can completely recreate the image if it’s simple – or at least something very close to it. Or we can try to blow it up and soften out the pixelated edges, making the detail in your image blurry rather than blocky. But neither are ideal and both will cost you time and money in art fees. And in some cases, if the graphic is too complicated to recreate and the resolution is ridiculously low, we may just not be able to print it at all.
The only thing you really need to watch out for with vector files is complexity. We sometimes receive files that we have to spend literally hours scouring to find a single element we need to select. Help us out by grouping elements together and not burying and locking important objects beneath layers and layers of clipping paths.
As far as we can tell, certain programs may create this over-complexity in the export process to create a pdf or eps file. We’re not really sure at this point which ones, so use Adobe Illustrator to create your artwork if at all possible, since that’s what we use.
The Bottom Line
Ideally, we want vector art that is no more than 6 spot colors and not over-complicated. If you have to send a raster file, make sure it’s around 300DPI or more.