When sending designs to be printed there are a range of technical factors that one must take into consideration in order to ensure that the finished product meets expectations. One of these factors is the file types that should be used for printing. This blog explains the various file formats and the processes of using them.
Digital images used in print fit into one of two categories: bitmap graphics or vector graphics.
Bitmap graphics are the most common image type and are used by digital cameras or scanners. Examples of common bitmap file types are .bmp, .jpg, .tif and .png. A bitmap image is a matrix of coloured dots called pixels, with each dot forming part of a larger image. The image's size is determined by its resolution- the width by height of the image in number of pixels. The higher the resolution, the more detail the image can have.
An example of an image losing quality as a result of low resolution.
The resolution of the image must be sufficiently high for the size at which it is displayed or the quality of the image will be noticeably worse. Gradients can appear less smooth, curved lines will seem jaggy and individual pixels may be obvious. When going to print, it is essential to ensure your graphics are a high enough resolution for the physical size they will be printed.
When printing materials with logos, diagrams or line art images a vector image file is preferable. Whereas bitmap graphics are made from an arrangement of pixels, vectors are made from an arrangement of lines. The reason vectors are more appropriate for these kinds of images is because they can be infinitely resized to be larger or smaller without any loss in image quality. The software shrinks or expands the image based on the relative coordinates of the lines rather than duplicating or removing pixels.
Not all software is capable of producing vector graphics. Software applications such as Adobe Illustrator or CorelDraw can be used to produce vector graphics and, in some instances, a logo can be converted from bitmap to vector. Images with minimal noise convert better to a vector format.
A bitmap graphic can be converted to vector to preserve quality up close.
Although vectors and bitmaps are created differently, if they are used correctly then the end result will be effectively the same. So long as the image is processed correctly, it will not lose quality. As a general rule, bitmaps are typically used for photographs while vector graphics are used for abstract images such as logos. In spite of this, it is often difficult to tell the file type of an image from its appearance alone.
Another option is to submit a Portable Document Format file, or PDF. PDFs are similar to the documents used by text processors like Microsoft Word except that they fix all of the text, image and layout elements in place. This ensures that the design will look identical no matter which software it is viewed in or who views it so that the printed product will be consistent with its onscreen design.
If submitting artwork for print which is not in PDF format, it is better to send the individual files themselves as opposed to inserting them into a text document and sending that. This is because files such as Microsoft Word will compress the images in order to reduce their file size and save computer memory. This can cause the image's resolution to be diminished resulting in a lower quality result when it is printed.