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    DTG vs. Screen Printing Art Files

    One of the advantages of DTG vs. screen printing is the reduction in time it takes to prepare the artwork. No need for color separations on different screens for multi-color jobs. With digital printing, an image with ten colors takes the same amount of time to prepare as a screen print one color image. The term “digital printing” covers several different types of printing, but they follow the same technique: a computer generated art file and either a printer or cutter to create a print for application on a t-shirt. Some popular digital printing options include a direct to garment and vinyl cutting.

    The exception to this is when you are sublimation printing. It is impossible to lay a white underbase; liquid sublimation dyes work by binding directly to your shirt fibers and a underbase would create a barrier. Its best to use sublimation printing on white or light colored fabrics that have a high percentage of polyester.

    Raster vs. Vector Images
    Raster images, as opposed to vector images, are recommended for digital printing. Raster graphics are created by using a grid of horizontal and vertical pixels to make up an image. Vector images, by comparison, use a series of lines and curves. This often produces a large solid area. These large solid areas tend to be unforgiving when digital printing, which relies on creating their images line by line. Often, printing big areas like this can result in unevenness and streaking - or “banding.”

    GIMP and Photoshop are two image manipulation programs that will allow you to create images suitable for digital printing. There are advantages and disadvantages of both, and often times it comes down to preference. Another program is Corel, and is more common with those who have a screen printing background since it is great for spot color work. Photoshop is great for photo-realistic images.

    Choose the right file type. Even though you often get JPG images with a white background, what you really need is a PNG file with a transparent background. Just as with screen printing, you can’t make a proper underbase when the file has white (or a shirt color) around the image. Learn how to remove backgrounds so there’s transparency around the image. Most raster image processor (RIP) software for DTG has features to “knock out” the background. There’s also a lot of inexpensive third-party software that can do this.

    Adjust your image resolution. You often get low-resolution 72 dpi images that are small in physical size. The first thing to do is go to Image/Image Size and upsample the image to 200 to 300 dpi and make it the correct physical size. This minor improvement will eliminate “jaggies” and smooth the edges.

    Improve low-quality JPG images. If the image was a low-quality JPG file, you might see “artifacts” and “blocks.” Unlike screen printing where such imperfections might show up in the final print, these problem areas may not be as noticeable on a DTG image. If your file is a low-quality JPG image, you can use off-the-shelf JPG enhancement programs (very inexpensive) to improve the image and remove artifacts and boxes.

    Improve your color saturation. This is a biggie. The conversion from RGB to CMYK reduces color saturation, and when bringing images from a vector program like Corel or Adobe Illustrator into Photoshop, there can be a color shift and dulling of the colors. Go to Image/Adjustments/Hue Saturation and move the Saturation slider up about 10 to 20 points. Don’t overdo it – just get the colors to pop a little.

    You can also help an image by using the Tone Curve to improve contrast. I like to use what I call an S Curve. It darkens the shadows and lightens the highlights and can make a huge difference in a flat image. Go to Image/Adjustments/Curves.

    Sharpen the image. Photoshop has a great Sharpening filter that can enhance/improve the edges of the image when used correctly. Go to Filter/Sharpen/Unsharp Mask (don’t let the name fool you) and start with a setting of Radius 1.0, Threshold 6.0 and Amount 250. Then move the Amount slider up or down. Make sure Preview is checked to see the effect, but always go back and forth so you can see the change to the image.

    Fix black and white areas. What appears to be solid black or solid white on the monitor is often not so. Open the Info Panel (Window/Info) and stick it somewhere so you’ll never close it. I use this panel all the time – it reads density levels. Select the eyedropper tool (this panel works with most tools) and place the tool over areas you think are dead black. Dead black is 0 levels of RGB. Any reading other than 0 means you won’t have dead black in that area. You will end up with a dark gray. Do the same for white areas. Dead white is 255 levels of RGB. Any other reading means your RIP will try to put a small amount of color there. You can adjust these areas using Tone Curve.

    Most DTG software will accept .JPG, .PNG, .TIFF among other formats. JPG is only good on light garments that do not use white ink, otherwise the background of the image will print white ink.
    You must save or export your files to PNG or TIFF to preserve transparency. I recommend saving your print files as PNG. PNG allows you to preserve transparency, maintains resolution, and is a modern, universal format.

    To save your print ready images in Photoshop or Paint, go to File > Save As > PNG. In Illustrator or Draw, you must export your image, go to File > Export > PNG.

    If you are creating your own artwork in a raster program always ensure you have a transparent background layer. A transparent background looks like a white and grey grid. If you see a white or colored background and you do not see the transparency grid, your printer will print the solid background on dark garments.

    When exporting from a vector program, size the artwork to the approximate print dimensions, and export as .PNG at 300dpi. Raster versus Vector Artwork

    Raster artwork is pixel based, meaning its resolution is dependent on how many pixels fit within a square inch or DPI (dots per inch). The higher the DPI the more clear and higher quality an image will print. Raster art is typically created in Adobe Photoshop, Corel Photo or Paint.

    With raster artwork you cannot increase low resolution images; you can only decrease resolution. For example you can’t take 72dpi art and make it 300dpi but you can take 300dpi art and make it 72dpi!

    A 72dpi image at 10”x8” is not sufficient enough quality for printing on a garment. The image will be too pixelated and not allow for crisp clear printing. If you try and make the image larger, the resolution will degrade more, and the end image result will be unacceptable.
    A 300dpi image at 10”x8” is sufficient, and also allows you the opportunity to increase the dimensions of the image while still maintaining decent quality. It’s important to remember the larger you make a raster image dimensions, the more the image quality will degrade.

    Now there is one exception regarding resolution. If you have an image with extremely large dimensions, say 3,200 pixels by 2,400 pixels (45”x34”) at 72dpi, there is sufficient dpi at these large scales that you can reduce the image dimensions to fit within your print perimeters and still maintain a high quality print. Recap of raster artwork

    Design your art at high resolution and large file dimensions. This gives you the most versatile platform for maintaining a high quality print. I like 300dpi and around 14”x16” for a standard front or back print.

    Avoid low resolution, small dimension artwork. You have no way to make it better than the original.

    Remember, it’s okay to use very large dimension art of low resolution if you plan to shrink the artwork down. Vector artwork

    Vector artwork is made in Adobe Illustrator or CorelDRAW. Vectors are created using mathematic equations within points, lines, and shapes to create images that maintain clarity when scaled, up or down, without any loss of quality.

    Vector artwork is extremely common and many designers prefer using vector programs. But be aware most DTG software will not read vector art files, therefore you must export your vector artwork to a raster format. RGB, CMYK, and File Optimization

    RGB is an additive color model where Red, Green, and Blue light is added together to form a color gamut. RGB input is typically used on most all electronic devices, TV, Computer Screens, etc. RGB offers a larger color gamut than CMYK.

    CMYK is a subtractive process requiring a white background using 4 colors, Cyan, Magenta, Yellow, and the Key (black ink). CMYK is the standard process for most all common digital printing processes. Most direct to garment printers, such as the Epson F2000/F2100 print with CMYK + White ink.

    Even though your printer prints in CMYK, its best practice to design in RGB for all print applications for the following reasons:
    • CMYK file sizes are about 25% larger than RGB.
    • Most filters and image enhancements are only available in RGB color mode.
    Web art and most printers require RGB color mode so there is no need for conversion from CMYK.

    • Create high resolution artwork at 300dpi, or 72dpi with extremely large image dimensions.
    • Save artwork from Photoshop or export from Illustrator, to ensure transparent background, PNG preferably.
    • Design or convert artwork to RGB if already CMYK.
    • Follow the instructions above from Great Dane Graphics for pre-printing file optimization.