“It’s not the good tint of red”, “the picture is not clear”, “can we redo it ?” Too often, it is once the file is printed that we realize the problems, while the initial file seemed perfect. The main reasons are the quality of the initial files and the use of inadequate formats for the needs. This is why we have decided to make a short focus about the different file formats you may use for online printing.
AI, PDF, PSD files... Every format has its function. Are they all equal ? What are the differences ? What format for what use ?
First, let’s see the difference between the two main file formats : vectorial (with lines) and raster (with pixels).
Vectorial VS Raster
A vectorial file is based on a geometric logic, mathematics formulas and it functions with a system of coordinates. Thus, a vectorial file is only composed by geometric figures and lines.
These lines are not pixelated and their outlines are smooth. The file elements can unlimitedly be reduced or enlarged without degrading their quality.
The vectorial files (AI, PDF and EPS from AI, SVG…) are mostly used for graphics and printing.
The raster file is materialized by a big grid pattern made of pixels. Pixels are small colored squares, invisible to the naked eye. When put together, they make an unified whole : your picture.
When the image has low resolution (few pixels / cm²) with a raster format, the squares appear bigger, the outlines are less precise and the picture gets blurred. It is usually said that the picture is “pixelated.”
Except the very composition of every file, it is the main difference between vectorial and raster.
The raster format files (PSD, JPG, PNG, PDF and ESP from PSD, etc) are used in photography, websites and social networks.
To get the best finish for logos and texts, a vectorial file (with clear lines and enlargement that doesn’t affect quality) should be used. For photos, a good-resolution raster file would be used.
Importance of the different file formats
There are many existing file formats. We decided to only focus on the 4 formats we mostly use : AI, PSD, PDF and EPS.
The AI files are generated by the most popular vectorial design software, Adobe Illustrator.
A AI file contains the figures representing the original creation. Thanks to this format, you have an editable file composed of several vectorial strata.
Notice : It is possible to import a raster-format file in this vectorial file.
Using : design creation, high-quality printing, logos, texts...
The PSD format (Photoshop document) is a raster file, generated by the editor software Photoshop. .psd format is made of a set of raster layers (pixels).
To have the best printing possible, a good resolution (300 pixels / inch) should be used.
Using : the PSD format is mostly used for the pictures that can’t be vectorized (photos for example).
That is the vectorial and raster format that is the most used by printers.
Note : many softwares propose a PDF export. However, to be considered as a real vectorial file, this file needs to be exported by a vectorial software. For example, if a PSD file is exported to PDF, this one will not be a real vectorial PDF.
Using : the PDF format is used for visual communication tools, high-quality printings and logos.
The .eps format (Encapsulated PostScript) is the predecessor of PDF. It used to be employed a lot by professionals ; the vectorial attributes of a file are preserved by this format. Today, the .eps format has been replaced by a more flexible .pdf.
Using : Unless you have specific habits with the printer, .eps format is not used anymore.
You know the main formats for your printing files as well as their differences. In a few words, prefer as much as you can the vectorial formats (via .AI or .PDF from .AI) and .psd for photos. For more information, you can read Our advices to prepare your files before printing.