Why do you need a vector file?

Firstly, for the best quality display especially in print. For example, if you type a word in a text document and enlarge it by 400% of its original size, the quality will stay the same. This is because the typed letters are vector graphics which can be scaled to any size. However, if you place a jpg or png image and enlarge it by 400% of its original size, the image will lose quality and you will see jagged edges. This is most notable on curves because pixels are square and as you enlarge the curve you begin to see the squares making up the shape.
Bitmap file - Original SizeBitmap file - Enlarged

Secondly, vector files contain graphics which can be split apart and updated as separate elements. In contrast, a bitmap image is a flattened image and is more difficult to adjust.

What is a vector file?

To explain, there are two file types which are important to understand – Bitmap and Vector files.


Bitmap files

Firstly, a bitmap image is made up of a fixed number of coloured pixels (squares). For instance, you can think of them like individual building blocks – think Minecraft or lego. Therefore, if this file is enlarged, the pixels or building blocks enlarge. This means the quality will reduce the more it is enlarged. As a result, you will start to see the pixel shapes and the edges will look ragged like the example above.
For the best results, you need to use a bitmap file at precisely the size it was created or smaller. Photographic images are bitmap files. File types include .jpg, .tif, .png, .gif


Vector Files

Secondly, a vector graphic is created using mathematical formulas rather than stitched together pixels or building blocks. As a result, you can enlarge the file and it will retain its quality. Vector files can be created using specialist software packages. Vector graphics tend to be icons or logos or illustrations. File types include .ai, .eps, .svg, .pdf


Are PDF files bitmap or vector?

PDF files can contain vector graphics, however, the content of a PDF file can also be bitmap data. For example, if an image is saved in a pdf, the image part of the file will not be a vector graphic.
In short, the best practice is to keep original vector versions of logo files, icons, illustrations, graphs or charts. Keep them even if you do not have the software to open them yourself. Why? Most importantly, if a larger size is ever required, you will need the original source file to create it. That is when you will be asked “please supply this file as a vector file”.


What about photographs?

To answer that, photographs are bitmap files. Therefore, if you enlarge them to more than 100% of their original size, the quality will reduce.  Consequently, the maximum size a photograph can be displayed at good quality will depend on the size of the original image file. This will also depend on the quality of the camera used to take the image. Photographic images published online will be saved at a set size for that particular use. As a result, if you need to reproduce that image at a larger size, you will need the original image to get the best result.



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