PC based readers vs. handheld readers

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Computer screens have a much larger viewing area than that of handheld devices. This makes for easy viewing of magazines without having to resort to scrolling and panning around pages.

Web pages, books and newspapers can usually be reformatted on the client side to fit the available screen size. In contrast, magazines have a fixed layout and usually require extensive rework of the layout and formatting to be readable on handheld devices.

It is important to note that while some handheld devices may support very high pixel densities and therefore reasonably high screen resolutions, that the human eye is generally not able to resolve detail at pixel densities of much higher than 96ppi (pixels per inch).

The following table depicts the same magazine content as viewed on the Apple iPhone3, iPhone4, iPad, Amazon Kindle and a standard PC screen. In addition to lower screen resolutions, text size on the iPad is 33% smaller, on the iPhone 3 and Kindle 66% smaller, and on the iPhone 4 more than 3 times smaller than the equivalent text on a PC screen. This increases eye strain for the reader and makes it much harder to read the actual magazine content on these small devices.

Device screen size comparison

iPhone 3

Pixel density: 163ppi
Resolution: 480 x 320 pixels
Screen size: 115mm x 61mm

iPhone 4

Pixel density: 326ppi
Resolution: 960 x 640 pixels
Screen size: 115mm x 59mm

Kindle 3rd. generation

Pixel density: 167ppi
Resolution: 800 x 600 pixels
Screen size: 122mm x 91mm

iPad

Pixel density: 132ppi
Resolution: 1024 x 768 pixels
Screen Size: 244mm x 190mm

24” PC screen

Pixel density: 96ppi
Resolution: 1200 x 1920 pixels
Screen size: 493mm x 560mm

Magazine viewed on a 24" PC Screen

 

Screen Pixel density vs. Screen Resolution

Pixel density refers to the number of pixels or dots in a measured screen area. Generally speaking, the resolution of a computer screen is a factor of the visible screen size (area) multiplied by the pixel density.

Most computer screens have a pixel density of about 96ppi (Pixels per Inch). This gives us a pixel size of about ¼ of a millimeter (0.26mm). The human eye can just barely resolve detail at this level which is why (unlike screen sizes) screen pixel densities have not improved much over the last 15 years.

In the print media, pixel densities of 300dpi (dots per inch) are quite common and pixel densities of as high as 1200dpi are sometimes used in “glossies”. Higher pixel densities gives a more “photo quality” look and could add even finer detail, but doesn’t add much more discernable info.

The mistake that people sometimes make is to compare the screen resolution of different devices without taking into account the pixel density. For example, the iPhone 4 has a pixel density of twice that of the iPhone 3 (see table below). This results in a screen resolution of 4 times that of the iPhone 3. As shown below, the same information displayed at exactly the same resolution on the iPhone 3 and 4, becomes unreadable on the iPhone 4.

The bottom line is that more pixels per inch do not mean that more information can be shown on a screen. More pixels per inch make fine detail stand out more and makes for smoother curves, etc.  Text will also become slightly crisper, but it does not mean that text can be made much smaller. The limitations of the human eye are still the limiting factor.

The table below shows the same text as it would look on Apple iPhone3, iPhone4, iPad , Amazon Kindle and a standard PC screen

Device screen resolution comparison (192px square image)

iPhone 3

Pixel density: 163ppi
Dimension: 30mm (1.2”)
Sample size: 192×192 pixels

iPhone 4

Pixel density: 326ppi
Dimension: 15mm (0.6”)
Sample size: 192×192 pixels

Kindle 3rd. generation

Pixel density: 167ppi
Dimension: 29 mm(1.15”)
Sample size: 192×192 pixels

iPad

Pixel density: 132ppi
Dimension: 37mm (1.45”)
Sample size: 192×192 pixels

Standard PC screen

Pixel density: 96ppi
Dimension: 51mm (2”)
Sample size: 192×192 pixels