For commercial printing, there are two types of files to choose from, raster and vector. Let us first understand these 2 file types and then we will compare strengths and weaknesses of both for commercial printing.
Raster images are also popularly known as bitmap images. A bitmap is basically a grid of squares or pixels. Each such square is coded in a specific hue or shade which collectively define the complete photographic image.
The quality and appearance of a bitmap image is determined based on 2 criterion, size and resolution. Bitmap size is generally expressed in mm or inches while the resolution refers to the density of pixels and is expressed as DPI i.e. Dots Per Inch. For better print quality it is recommended to use higher pixel density. The size and resolution directly contributes to the physical file size of the image. Higher the DPI, higher the physical file size will be.
It is generally recommended to use 72 DPI images for online web usage and 300 DPI images for commercial printing.
Vector graphics are based on mathematical formulas that define geometrical shapes like lines, curves, polygons and others. Vectors are basically points connected by lines of various shapes, filled with solid or gradient colors.
Because vector graphics are made up of mathematical calculations, they have infinite resolution. When scaled, the math creating it holds up and recalculated to always show smooth, clear edges and details.
- Bitmaps can represent complex, photographic images. They are best used specifically for digitized photographs, scanned artwork or detailed graphics. Whenever you need to add texture, fills and other special effects to your image, use bitmap. While vector images are preferred when you need well defined structural images with clear-cut and defined shapes. Mostly the human created images like logos, business cards, illustrations, page layouts, fonts and other such images are better suited for vector format.
- As bitmaps are composed of a finite amount of information (size and resolution), they are not effectively scalable. If you try to increase the size of a bitmap image, it basically increases the total pixel count, and as there is no information to render these additional pixels; hence the software generally interpolates the pixel properties to create the best possible arrangement leaving the image blocky or jaggy. While vector images are quickly and perfectly scalable. They have infinite resolution and can be scaled to be very large without losing quality. As the governing mathematical formulae apply identically to graphics of any size.
- Bitmap images tend to be larger in size as they store the contents of millions of tiny pixels like X, Y coordinate, color etc. for each pixel. While vector images are considerably smaller in size as they just store the math involved in recreating the image. Hence vectors are more suitable for sharing, e-mailing and storage.
- Converting a raster image to vector is very difficult and not recommended for commercial use. While almost all vector image editing software can easily rasterize the vector image to render perfectly acceptable output.
- Bitmap is a universal image format. Almost all image editing programs can work with simple bitmap files without additional system overheads. While for working with vector graphics one needs a program that can understand the math behind vector creation and can modify its shapes, arrangements and colors.
With this post I have tried to explain the bitmap and vector images individually as well as compared them on some main criterion of differentiation. In my opinion, vector graphics are the best choice if your image is targeted to be printed for advertisements, banners, labels or likewise, while go for raster for printing your photographic images or detailed artwork.