Vector vs Bitmap
Often clients don’t understand vector vs bitmap. One of the questions we often field is “I have a photo or a picture from the internet, can you put it on a shirt for me?”. The short answer to the question is yes. From there we have a few approaches at making your shirt. To obtain good or at least decent image quality, the picture has to be good from the beginning. If we are working with a small and less than average photo our art department more than likely has to step in and work their magic. Initially we ask all of our customers if their artwork is in a vector format such as .eps, .ai, or .cdr. A yes answer is good news, but a no answer isn’t the end of the world, it just cost the customer a little more to achieve production ready art. For the sake of cost we discourage design in bitmap programs like Photoshop, unless the art is created to scale and doesn’t need to be enlarged or shrunk on the garment. Some applications require a vector format such as vinyl decals for vehicles or signs. This post is meant to shed light on the differences between vector and bitmap images and will reveal the reasons vector images are the superior form of digital art for garment and sign production.
A vector image is a collection of connected lines and curves that produce objects. When creating a vector image in a vector illustration program like Adobe Illustrator, node or drawing points are inserted and lines and curves connect nodes together. This is the same principle as connect the dots. Each node, line and curve is defined in the drawing by the graphics software by a mathematical description. Each aspect of a vector object is defined by math including node position, node location,
line length and on down the line. Text objects are created by connecting nodes, lines, and curves.
Vector images are defined by math, not pixels. They can be scaled up or down without any loss of quality. When an illustration (drawing) program sizes a vector image up or down, it simply multiplies the mathematical description of the object by a scaling factor. For example a 1” square object would need to be multiplied by a factor of 2 in order to double in size. The math is simply recalculated to produce an object twice the size of the original. Because vector images scale up or down without the loss of image quality, they can be output at any resolution that a printer is capable of producing. Unlike bitmaps, quality is not limited by dots per inch or scanning resolution. This is a big reason that vector graphics are so popular for clip art.
A bitmap image is a collection of dots called pixels. Each pixel is a tiny colored square. When an image is scanned, the image is converted to a collection of pixels called a bitmap. Scanned graphics and web graphics (JPEG and GIF files) are the most common form of bitmaps.
The resolution of a bitmap or scanned image is expressed in terms of dots per inch or dpi. A printer or scanner’s resolution is also measured in dots per inch. Typical desktop laser printers print at 300 dpi. Our printers print at 720 dpi; however the quality of the output is dependant on the dpi of the original artwork. The higher the dpi the smoother and cleaner the output. Take a 300 dpi bitmap and increase the size in a graphics program, and instantly you have a bad case of the “jaggies”. The only thing that happened is that the tiny pixel squares got bigger and created jaggy edges on your image. In other words, bitmaps do not scale up very well.
...TURNING YOUR ARTWORK INTO VECTOR
If you aren’t familiar with vector programs or don’t know how to convert your artwork into vector, our art department can assist you for a fee. Please call us with any questions.
~ Superluxe Screen Printing