When creating graphics for shirts, not all file types are created equal. To get the best looking graphic for your logo, sign, shirt, or printed material, here is a brief overview of what kinds of files to use.
Bitmap vs. Vector images
Digital images can be divide into two distinct categories, bitmap images and vector images.
Bitmap images are images composed of a pixel grid. Each pixel is a square that is assigned a color and arranged to create an image or photo. Bitmap images are resolution dependent and therefore it is difficult to increase or decrease their size without losing quality in the image.
The most common bitmap image is a .JPG, this is what photos off of your camera and the internet are commonly. .JPGs are great for storing and uploading because the file size and their compatibility with programs and the internet. For printing purposes, .JPGs are not the best way to go. Because .JPGs are resolution dependent, they are likely to print smaller and at a lesser quality than seen on your computer screen.
Bitmap formats include:
Vector images are created out of scalable objects. Objects are created from mathematical formulas rather than pixels, so they can be scaled without any loss, and look best when rendered. Objects in vector images can be changed and modified without degrading any information of the image. For printing shirts, layered vector files are the best to use to get good quality.
Vector formats include:
.AI (Adobe Illustrator)
.SVG (scalable vector graphic)
Layered vs. Non-Layered Files
Layered images are files composed of many layers stacked on top of each other like transparencies. Non-layered images are compressed images that can not be separated to edit.
Non-layered images are usually bitmap images, and can not be separated easy. .JPG, .PNG, .GIF are all examples of non-layered images.
Adobe Photoshop and Illustrator are the two most commonly used programs to make layered images. Since objects are created in different layers, it is easier to edit them individually, but files are only layered if you make them that way. Layered images are easy to reuse and reproduce, since they are easily editable and easy to print.
.AI (Illustrator) files are layered vector files and the easiest to edit, manipulate, and print. Since vector files are not pixel or resolution based, the look sharper and are easy to resize and modified. For screen printing, this is the best way to go! Because we can separate images by color, we can create the best looking graphic on your shirt. **Keep in mind, saving a non-layered file like a .JPG as a .AI file does not automatically make it a vector or layered image.**
Some .PDF files are also layered files if they are formatted and saved properly. For example, in Illustrator, when saving a file as a .PDF, you must choose to preserve illustrator editing capabilities to still be a layered file.
.PSD (Photoshop) files are usually layered, as long as individual layers are made. To save it as a layered file just hit save and .psd should be defaulted. If you save as a .JPG or .PNG, the image becomes compressed to one layer and is not editable anymore. **Again, saving a .JPG or .PNG as a .PSD does not automatically make it a layered image.**