Quality control for digital color separation – Preparing Files
Bringing an images quality up to standard prior to color separation saves time during the separation process, and always results in a better print. This tutorial deals with image preparation prior to color separation in the RGB mode, and outlines the main image quality issues for screen printers and their solutions.
Color – Resolution – Line quality – Image Quality – Transparency – File Format
1) Assigning Color. The first step when opening a new document for separation is getting the colors set with the proper color profile. Next, converting the file to Adobe RGB provides a larger color gamut and allows for improvements to the images color range. To preserve changes and edits save a copy of the file in the Adobe Photoshop format (.psd)
2) Check the resolution. The next step is to make sure our image’s resolution is adequate for the print size. Depending on the image type, resolutions between 150 and 300 pixels per inch is recommended.
In most cases increasing an images resolution by resampling will not improve image quality. However, If we plan on adding graphics or text, masking the background or making adjustments, increasing the resolution is important.
3) Asses the line quality. Line quality refers to the appearance of edges and lines such as graphics and text. The quality of these elements is dependent on the images resolution as well as the images source and any post processing. Line quality can be improved, although it is often necessary to reset compromised text and graphics for good results.
4) Asses Image quality. If necessary, bring the overall quality of the image up to prepare it for separation. This includes reducing any noise or artifacts that may be present, setting the black and white points and increasing the saturation and contrast as needed. Poor contrast, digital noise. jpeg compression, and overly soft or rough edges can all be handled better before beginning the separation process.
5) Ensure a good transition from the image area to a transparent background.
To isolate the white screens in a color separation an image should needs to be properly masked onto a transparent background. Using a transparent background provides control over the transition from the garment color to the printed colors. Backgrounds can be removed manually using layer masks, or with help using tools such as the extract filter, magic wand or color range selection. For printing on colored garments, layered images should be previewed on black, gray and white backgrounds.
6) Save an adjusted, multi layer file for reference and a merged, single layer file for separation. Finally, save the adjusted file with all its original layers as well as any new layers. Merge this document into a single layer image on a transparent background, and save as a copy, for the color separation process. This creates 3 files:
• The original file.
• The adjusted, multi-layer RGB file.
• A single layer RGB file with a transparent background.
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