Raster vs. Vector images: What’s the difference and when to use them.

vector-versus-raster-packaging-print

When purchasing printed cardboard packaging, you have a variety of print options readily available to you.  We do our best to make navigating the development of your first bespoke packaging as easy as possible, but if you haven't dealt with any printed materials before, inevitably there is going to be some terminology that you are not familiar with: including the terms raster and vector.  

 

In this article, we aim to bust the jargon surrounding image types.

When considering these print options, it is important to understand what type of imagery you should be using to produce clean, high quality print designs.

What is a Raster image?

Raster (or bitmap) graphics are images that are in the form of digitised photographs or detailed graphics and illustrations. They are saved in the below formats:

  • .bmp (Bitmap Image File)
  • .gif (Graphics Interchange Format)
  • .jpg (Joint Photographic Expert Group)
  • .pdf (Portable Document Format)*
  • .png (Portable Network Graphic)
  • .psd (Adobe Photoshop Document)
  • .tiff (Tagged Image File Format)

If you have a file saved in the above format, it will always be a raster-image.

*A PDF can contain both raster and vector images.

Raster graphics are comprised of lots of tiny, colour squares called pixels. In large quantity, these pixels form an overall image, like a mosaic.

See the below raster-image which shows an enlarged area of the pixels. You can see the individual colour squares which are a key indicator of a rasterized image.

What_Is_A_Raster_Image
An example of a raster-image exported at 72ppi (pixels per inch). Images posted on the web are typically set to this resolution.

When a raster-image is created, it contains a fixed number of pixels.   The more pixels per inch, the smoother the shape and blend of colour which in turn, produces a higher quality image. The less pixels included per inch, the larger the pixels become and the more noticeable they appear. This starts to distort and blur the image.

The quantity of pixels included in an image is defined by pixels per inch (PPI). A low-quality image is typically set to 72PPI whereas a high-quality image is typically set to 300PPI.

Since raster images are comprised of a fixed number of pixels, the image cannot be scaled up in size without sacrificing its quality. If you enlarge the image, the pixels stretch to fill the expanding surface area and the existing pixels become more apparent. This is known as pixelation. The general rule of thumb when re-sizing is to downscale only.  We do not recommend using images above 100% of their original size to ensure you achieve a good result on your personalised printed packaging. 

 

What is a Vector image?

Vector or Scalable Vector Graphics (SVG) consist of dots, connected by paths and curves which are controlled by mathematical formulas within the software. In its simplest terms, think of the puzzle game dot-to-dot; where lines and curves are drawn to connect the dots and reveal the outline of an object. These formulas capture shape and colour to build an overall image. The great thing about these formulas is that they make vectors infinitely scalable, keeping the quality the same as the original at any size.

Vector graphics can be saved in the below formats:

  • .ai (Adobe Illustrator document)
  • .eps (Encapsulated PostScript)
  • .pdf (Portable Document Format)
  • .svg (Scalable Vector Graphic)

See the below vector-image which shows an enlarged area of the curves and lines that make up the overall image.

What_Is_A_Vector_Image
An example of a vector graphic image.

It is recommended that Adobe Illustrator is used to create and edit vector images. Avoid Adobe Photoshop as this still creates raster-based images, even when saved as a vector.

 

Which image type should I be using for my printed packaging?

Whilst we would always recommend using vector graphics the true answer should be determined by the print process you wish to use.

Flexographic Print

what-does-a-print-stereo-look-like-Dairi-Pak
Example of a flexographic print stereo (sometimes called a printing plate).

What should I use?

Vector images.

Why?

We always recommend vector images due to the printing process. Flexo is printed by pressing polymer against cardboard. This polymer is an exact replica of the artwork.

If a raster image has any pixelation, the jagged edges shown in the artwork will also show on the print. This will give you a less attractive print when compared to using a vector graphic.

That being said, vector imagery cannot always replace high detailed raster imagery. If a raster-image must be used, always opt for 300PPI or more.

 

Digital Print

digital-printer-cardboard-Dairi-Pak

What should I use?

Vector or high-quality raster images.

Why?

Digital printing works on a similar principal as an inkjet printer that a PC would print to. Printer heads spray liquid ink through microscopic nozzles as the substrate passes underneath them. As there is no contact between the cardboard and the printer heads you can use vector or high-quality raster images.

 

Litho Laminate Print

litho-lam-print-example-Dairi-Pak

What should I use?

Vector or high-quality raster images.

Why?

The litho laminate method uses printing plates that print on to paper liner rather than cardboard. This achieves fine detail and high-quality print because it has the advantage of printing on a smooth surface. The paper liner is then attached to the corrugated fluting.

As litho laminate can print finer detail, the use of high-quality photographs and raster illustrations can produce high-end retail packaging.

We hope that will help you navigate your way through the initial graphic design process whether you are doing that in house or will instruct a graphic designer.  We look forward to discussing your customised cardboard printed packaging design.  Please do not hesitate to contact one of our friendly and knowledgeable team.  E: sales@dairi-pak.co.uk T: 01939 260342

How can we help you? Get in touch about your packaging requirements

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