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digital images

You Say You Want Resolution...

You Say You Want Resolution...

There always seems to be a little bit of confusion over resolution especially when trying to compare the terminology between print and digital. Since we re-purpose print files onto digital platforms we thought we would shed some light on the matter.

Let's look at the word 'resolution'. According to Wikipedia, image resolution is the amount of detail that an image holds. The amount of detail a digital image can hold is dependent on the number of pixels. So, wait, what is a pixel? A pixel represents the smallest element that can be manipulated in a digital image or on a digital display (wikipedia). Huh?

Let's see if this helps. Think of an image. Any image. A wedding photo, family picture or a 'selfie with your bestie' (FIG. 1). Now place an imaginary square grid, like a sudoku puzzle, over top of that image so that it spans outward to each edge (FIG. 2). Although rudimentary - each one of those squares would represent a pixel.

The only problem with the above illustration is that each pixel can display a number of colours but only one colour at a time (FIG. 3). That means that your wedding photo would not be very discernible since sudoku puzzles only have 9 columns and 9 rows (81 squares or pixels). But what if we changed the number of columns and rows in the square grid? What if we made the grid 100 columns by 100 rows? What about 1000 columns by 1000 rows? If we used the 1000 x 1000 grid that means we would have 1,000,000 individual squares of colour. If we placed the 1000 x 1000 grid over the wedding photo that means that the size of each square (pixel) in the grid would be much smaller (FIG. 4). It also means that more image detail would be available because of the increase in total pixels or squares (FIG. 5). The wedding photo would appear more clearly. That's resolution.

Digital resolution is measured in PPI which stands for 'pixels per inch'. Pixels per inch is a representation of the number of pixels that exist within one square inch. An image with a greater PPI has a better resolution than an image with a lower PPI.

What about printing?

When an image is being outputted to a printer it typically requires a minimum resolution of 300 PPI to ensure quality. Higher PPI values can be achieved but do not necessarily indicate better result. Why? The resolution quality of an image being printed is limited by the printing device. In other words you can't print a 300 PPI high resolution image using a dot matrix printer than can only produce 96 DPI. Wait a minute, you mean PPI right? No. DPI is kind of the resolution cousin of PPI. Printers apply ink in a linear fashion and DPI (dots per inch) represents the measure of the number of dots that can be 'printed' within a one inch line. Similar to PPI, the greater the number of DPI the better the print quality of an image. 

Display devices offer the same 'resolution conundrum' as print devices. The resolution of the input image is limited by the output resolution of the device. Despite the term 'high definition' being used to describe computer displays and television screens they are relatively limited in their ability to produce 'print quality' resolution. Monitors tend to have a display resolution between 72-96 PPI. The MacBook Pro with retina display has a display resolution of 144 PPI and represents the best retail available output. So can I tell the difference between a 300 PPI image and a 150 PPI image if I am viewing it on a 96 PPI display? Not likely. So why does Flip Page Publishing suggest higher resolution images in Flip Page editions when most displays can't output that quality? There are a couple of reasons; 

  1. Flip Page software offers a 'vector zoom' tool which allows a user to magnify page content. Our vector zoom is loss-less which means that if a high res. image is provided as input it will display crisp and clear when magnified. Conversely, low resolution images which are pixelated or grainy will display as such when magnified.
  2. When 'Print' or 'PDF download' tools are made available in a Flip Page edition a higher resolution PDF will offer better print quality compared to a low resolution version. 
  3. High resolution images that are rendered as raster within a PDF file tend to inflate the size of the file dramatically. This is not the case with Flip Page editions so there is no reason to lower resolution. 

When it comes to displaying your brand, your print media, on a digital platform, aim high. High resolution.