In her first piece for us this year, resident digital printing expert Debbie McKeegan gives her advice on understanding resolution, colour, ink sets, and textile manufacture. Debbie has developed many new digital production practices, and speaks as an authority on digital design and print worldwide.
Good design is in the detail, and design is just the first part of the creative process. In this article I thought it best to go over some of the process that we all take for granted: resolution and colour. With the use of digital print, and the endless possibilities now available to designers of Fashion and Interior products, almost anything is possible visually. However, to achieve your expectations it’s important that your files are set up correctly. And so let us start at the beginning – of the creative process and of your journey to the perfect print.
Resolution is a greatly misunderstood topic. Put simply, once created, the resolution of your image cannot be improved unless the file is printed at a smaller scale. Often, clients get confused by terminology and assume that the file size (measurement in centimeters) is the key to high quality output. Beware, you cannot make your file size bigger and improve the printed resolution; you will only make the onscreen image size bigger, and the resolution (print quality) and the final image quality will decrease in sharpness.
In the digital print marketplace your printer uses DPI (dots per inch) as a benchmark for their print process. Therefore, all files must be created at the correct DPI. Every printer uses their own variations dependent on machinery, and the software to be used, alongside the requirements of the substrate to be printed and the designer’s creative brief.
As a general rule I would advise the textile designer to create their patterns at actual print scale (final size) and at 300dpi. Once created your image may be reduced to 180dpi for print purposes if needed by your manufacturer. The print specifications for textiles and wallpaper vary greatly from high resolution graphic / photographic industries and should not be confused.
Create your designs at actual scale and at 300dpi using RGB mode for multiple uses.
Colour is probably the most misunderstood topic of all …from the Textile designer’s perspective (and I offer my advice as best practice for multiple products across multiple marketplaces). The main issue is expectation. Can you really expect a printed file to match your screen without any calibration? The short answer is no. Every screen looks different, just as your own screen looks different in different light, day and night. As humans we are unique, and every human eye also sees colour differently.
The most common colour mode for the manufacture of Textiles using web applications and software, such as Photoshop, is RGB. All digital devices use the RGB colour mode – that’s computers, televisions, even your mobile phone – which must not be confused with CMYK: another topic altogether.
CMYK is predominately used in the graphic and signage events industry to print files and products created for display alongside printed paper media. That’s because CMYK gives a 4 process colour gamut, using Cyan, Magenta, Yellow and Black in the print process, whilst also giving a smaller colour space and different colour palette entirely than RGB. Yes, the colour space is smaller than RGB, however, for graphic print industry applications this process is often used as colour is measured by the percentage of ink to be printed and reflects the older process of printing pre-digital using plates.
Beware: if you create your file using CMYK the onscreen view will not match your printed media (digital textiles RGB) unless converted correctly.
So what’s RGB and why is it so important? Currently it’s the closed measure of colour across multiple devices. It gives a visual spectrum of colour as used in your design. However, this is where the main problem for designers gets a little more complicated and it’s necessary to understand the Textile print process.
Understanding Ink Sets and Textile Manufacture
Pigment inks and reactive inks are the main ink sets used for the printing of cotton and linen fabrics; the fabric is coated to accept the inks and variable process methods thereafter fix the ink to the cloth. Polyester, on the other hand, is printed using dye sublimation inks. Here the design is printed onto paper and then transferred using heat to the final substrate.
In both fabric types the problem is variables – firstly, ink set suppliers. Each ink set and the colour produced at the point of print vary by supplier. Once printed the colours will vary again dependent on the substrate. As a simple example dye sublimation gives a greater yield of colour, producing a wider gamut of intensity and shades. Cottons and linens offer a more muted colour palette as is typical of home furnishings, with the added complication that they are organic substrates at origin, and all processing during spinning and weaving, bleaching that is necessary to produce a printable cotton product, changes the chemical composition, which will also affect final processed colour.
The print provider must profile their ink sets to the substrate that’s to be printed and, where possible, calibrate their CAD and CAM. However, colour gamut is also an important factor. The colour displayed on the screen in RGB mode may be out of the field of range (i.e colour space) that your printer technology can actually achieve. It’s impossible for this information to be share freely without the printer taking an in depth look at every file and advising the client. Some print providers have the software to do this and others do not.
It’s for the reasons above that where perfect colour replication is required it is essential that the designer samples their patterns with their chosen printer.
Lastly, I’d like to talk about how you should create and save your file. We have addressed RGB, and DPI (referred to by Photoshop as PPI) The most commonly used file type is TIFF. That’s because a TIFF is a high quality bitmap (pixel) image and saving in TIFF format does not compress colour information. It’s also important at this stage to select the colour profile. A good standard in our industry is Adobe RGB 1998, and is widely used by print providers to manage colour through generic RIP software. Simply put, selecting Adobe 1998 gives the print machine the gamut range of the file’s embedded colour space.
And that’s it. You’re all set up and well on the way to your perfect print. Please do remember to select your print partner carefully…
[*Image credit: www.digetex.co.uk]