How to prepare your files for DTG printing

This month Colin Marsh, managing director of Resolute DTG, talks through how you can efficiently and effectively prepare your files for direct to garment printing.

No matter what DTG printer you have, prints made from poorly prepared artwork will look dull and often pixelated. The process of DTG printing is inkjet, put good files in and good T shirts will come out, put bad files in and yes, you will get bad T shirts out.

Preparing files for DTG printing is a very similar process to producing files for other printing processes, two big differences are:

  • DTG prints can use white ink which is assumed by some file formats to be the substrate or paper which in many cases is embedded in the file as a background.
  • A DTG print may be a one off so you cannot afford to spend more than a few minutes repairing bad artwork or your profit is gone.

The good news is most software RIPs have built in features that allow for quick fixes for some of the most common errors. Below are a few tips to get these done quickly.

Backgrounds

These need to be removed before printing or you will end up with a white or coloured square where you should be seeing the colour of the shirt. This example is using the CADlink RIP. You can automatically remove a black background from within the print queue but in some cases using the wizard will give better results by tweaking the parameters to change what percentage of black is removed.

Automatic black background removal

 

 

 

 

 

 

 

When using the wizard it is possible to remove any colour from the file as long as you can click directly on it. This is a quick way to prepare JPGs for printing onto dark shirts without spending too long in an image editing package.

Wizard to change the colour removed or how much is removed

 

 

 

 

 

 

 

Vector or Bitmap

Both types of file are ok for DTG printing, however a Bitmap file can easily be made to look out of focus by using Anti-Alias in editing programmes in order to soften harsh edges or visible pixels. Anti-Alias is designed to create soft edges for viewing on a computer screen. The problem with Anti-Alias is, semi-transparent pixels are seen by the RIP when the under base is generated and will be given a white pixel in order for the colour to show when printed on top. This results in a white halo around the image. Using another plugin these semi-transparent pixels can be removed in the RIP removing the halo and allowing for colours to blend correctly.

Example Anti-Alias image vs. Vector file

 

 

 

 

 

 

RGB to CMYK

In order to generate the white under base automatically in most cases RIP software uses an RGB file format. This allows for an Alpha channel to be converted to a white layer automatically on import.

While this is a superfast way of generating an under base you can run into colour matching issues with RGB. It can generate much brighter colours when viewed on a computer screen that no printer not just a DTG printer can reproduce with ink. The CMYK colour range cannot reproduce these vivid colours and in some cases there can be quite a shift between bright colours like red, orange and blue.

Example of RGB on screen and what it will actually print like

 

 

 

 

Increasing the colour saturation within the RIP does a pretty good job of getting as close as possible to the original. This can be achieved by using either a plugin provided with the RIP or tweaking the curves in the profile. The latter is more complicated and should be done with caution if you do not have a good knowledge of colour management.

With these basic tips most of the most common problems associated with artwork files and DTG are covered.

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