Screen sizes

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The page compares screen sizes available on eBook Readers. This display size is usually given as a single number that represents the diagonal dimension of the screen. Next to the size of the screen the next important number is related to the number of pixels on the screen. This is usually summarized as a PPI (pixels per inch)

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[edit] aspect ratio

While the diagonal number is a convenient number to use for display size the important screen size is actually the area of the screen which determines the total number of letters and thus words that can appear on the page. The area is related to the diagonal size by the aspect ratio. This is a term that describes the relationship of the height of the display to the width of the display. For example a 5" screen that was 4" high and 3" wide would have a ratio of 4:3 or sometimes represented by dividing the smaller number into the larger as 1.33:1. The area of such a screen would be 12 square inches. A narrower screen would have a less reading area. For example a 5" screen with a ratio of 16:9 would be 4.35" high and 2.45" wide and have a reading area of only 10.6 square inches. Some PDAs and cell phones use a ratio of 3:2 on small pocket size devices although 4:3 is also popular.

Occasionally someone will want to fill the screen with an image by zooming it up or allowing it to be resized and wonder why there are spaces at the top and bottom or on the sides. This is caused by trying to display an image that has a different aspect ratio than the one your screen has. You need to remake the image with the correct aspect ratio or allow it to be distorted. Note that the aspect ration for an image must take into account any extraneous data that may be on the screen such as a title bar so the image may need to have a different aspect ratio than the screen itself.

[edit] PPI

PPI, pixels per inch, is the second number that is used to assess the readability of a screen. Generally the more ppi the better although there is a trade off of performance and battery requirements in generating the screen image when it contains more pixels. See Display#Screen Resolution

PPI and DPI (dots per inch) are related values and for a monochrome screen they are usually the same number. For color, typically 3 or 4 dots are needed to represent a single pixel. Some reading systems take advantage of the fact that the human eye cannot detect really small color pixels so they use sub-pixel sampling as a form of anti-aliasing to increase the apparent resolution of text. See Fonts for more information on this topic.

The term retina display is used to identify a high ppi screen, usually 250ppi or higher. It attempts to identify the upper limit of useful ppi values and considers the viewing distance as well as the ppi value. A small screen device would typically be held closer to the eyes than a large screen and would thus need a higher ppi value to be termed a retina display.

If the total pixel size for horizontal and vertical is not exactly the same as it should be for a given aspect ratio then the ppi for vertical may be slightly different than for horizontal or it may be the pixel is not square.

[edit] 4:3 ratio

This ratio is called the golden triangle as a triangle with sides 3", 4", and 5" produces a triangle with one edge at 90 degrees (a right triangle). This is the ratio used on most CRT monitors and is considered pleasing to look at although for eBook readers you are likely to prefer portrait mode. It is often used with eBook readers. The computer monitors have standardize the pixel sizes for this ratio as: 640 x 480 (VGA), 800 x 600, 1024 x 768, 1280 x 1024, 1600 x 1200 and 2048 x 1536 for square pixels. Many eBook readers use one of these standard values but may have screens that are not exactly the 4:3 ratio or may use pixels that are not exactly square. Computed PPI values may be different for horizontal and vertical for these reasons and an average may be shown.

approx 4x3 ratio
Size Dimensions Pixels PPI Area Sample Device
13.3" 271 x 203 mm, 10.67" x 8.0" 1600 × 1200 150 85.3 Sony DPT-S1
10.2" 207 x 155 mm, 8.15" x 6.1" 1280 × 1024 158 49.7 E Ink display
9.7" 203 x 140 mm, 8.0" x 5.5" 1600 × 1200 200 44
1200 × 825 150
197 × 148mm, 7.8" x 5.8" 2048 × 1536 264 45.2 iPad retina
1024 × 768 132 iPad 1 & 2
9.0" 183 × 137 mm, 7.2" × 5.4" 1024 × 768 142 38.9
8.0" 163 x 122 mm, 6.4" x 4.8" 1600 × 1200 250 30.7 PocketBook InkPad
1024 x 768 160
7.9" 160 x 119 mm, 6.3" x 4.7" 1024 × 768 163 29.6 IPad mini
2048 x 1576 326 IPad mini retina
6.8" 5.4" x 4.1" 1440 × 1080 265 22.2
6.0" 122 x 91 mm, 4.8" x 3.6" 1024 × 768 213 17.3
800 × 600 167
1440 × 1080 300 Kindle Voyage
5.0" 101 x 76 mm, 4.0" x 3.0" 800 x 600 200 12
640 x 480 160
4.3" 88 x 66 mm, 3.46 x 2.60" 800 x 600 232 9
3.5" 71 x 53 mm, 2.80" x 2.10" 320 x 240 114 5.9
2.4" 1.92" x 1.44" 320 x 240 167 2.8 Sansa Fuze

[edit] 16:9 ratio

Also known as widescreen, this is the standard for the new HD (High Definition) TV's and has also been used on many of the new computer screens. It is also known as 1.77:1. However computer screens are sometimes actually 16:10 (8:5) or have pixel counts that are slightly higher than would be normal for a true 16:9 screen. True High Defintion TV's are either 720p (720 x 1280 pixels) or 1080p or i (1080 x 1920 pixels sometimes called full HD). A small computer screen of 800 x 480 would actually be 800 x 450 if it were true 16:9 ratio. Either the screen is slightly wider (16:9.6) or the pixels are not square to accomplish this difference. Computed PPI values may be different for horizontal and vertical for these reasons and an average may be shown.

approx 16x9 ratio
Size Dimensions Pixels PPI Area Sample Device
10.6" 9.25" x 5.2" 1920 x 1080 207 48.1 Surface RT2
10.1" 214 x 135 mm, 8.53" x 5.33" 1280 x 800 150 45.5 Motorola XOOM
220 x 132 mm, 8.68" x 5.1" 1024 x 600 118 44.3
223 x 126 mm, 8.8" x 4.95" 1366 x 768 155 43.6 Asus Transformer T100TA
8.9" 7.8" x 4.4" 2560 x 1600 339 34.3
1920 x 1200 224
7" 155 × 89 mm, 6.1" × 3.5" 1920 × 1200 323 21.4
1280 × 800 216 PadFone X mini
1024 × 600 167
6.9" 152 × 86 mm, 6.0" × 3.4" 800 × 480 138 20.4
5.5" 4.8" x 2.7" 1920 x 1080 401 13.0 iPhone 6 plus
5.1" 110 × 66 mm, 4.35" × 2.62" 800 x 480 184 11.4
4.7" 4.1" x 2.3" 1280 x 720 315 9.4 Fire phone
1334 x 750 326 iPhone 6
4.5" 3.92" x 2.2" 854 x 480 218 8.6 PadFone X mini
4.3" 95.3 x 54 mm, 3.75" x 2.13" 1280 x 720 338 8.0
800 x 480 217
640 x 360 170
480 x 272 128
4.0" 88.9 x 49.3 mm, 3.5" x 1.94" 1136 x 640 326 6.8 iPhone 5
3.5" 3.11 x 1.73" approx 600 x 360 200 5.3

[edit] 3:2 ratio

This ratio is used on some pocket sized devices such as PDAs and cell phones with screens smaller than 4" although 4:3 screens are also used on these devices. It is sometimes shown as 1.5:1 and termed wide screen. The pixels on screens with a 3:2 ratio are often not square.

approx 3x2 ratio
Size Dimensions Pixels PPI Area Sample Device
12" 10" x 6.67" 2160 x 1440 216 66.7 Surface Pro 3
9.0" 7.5" x 5" 1920 x 1280 256 37.5 NOOK HD 9
7.0" 5.9" x 3.7" 1440 x 900 243 21.8 NOOK HD 7
3.9" 82 x 55 mm, 3.22" x 2.15" 480 x 320 149 6.9
3.5" 73.9 x 49.3 mm, 2.91" x 1.94" 320 x 240 116 5.6
480 x 320 165 iPhone 3
960 x 640 326 iPhone 4

[edit] Nomenclature

Certain sizes are considered to be standard sizes with specific names and screen resolutions. These include:

  • QVGA (320x240)
  • WQVGA (400x240)
  • WQVGA432 (432x240)
  • HVGA (480x320)
  • VGA (640x480)
  • nHD (640x360)
  • WVGA800 (800x480) or simply WVGA
  • WVGA854 (854x480) also known a FWVGA
  • qHD (960x540)
  • DVGA (960x640)
  • SVGA (800x600)
  • WSVGA576 (1024x576)
  • WSVGA (1024x600)
  • XGA (1024x768)
  • WXGA720 (1280x720) also known as 720P or simply as HD
  • WXGA800 (1280x800)
  • WXGA (1366x768) also know as FWXGA (sometimes 1360x768 to save memory)
  • XGA+ (1152x864)
  • WXGA+ (1440x900)
  • SXGA (1280x1024)
  • SXGA+ (1400x1050)
  • UXGA (1600x1200)
  • FHD (1920x1080) also known as 1080P
  • WUXGA (1920x1200)
  • UHD (3840x2160) also known as 4K

[edit] For more information

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