The Lumia 1020's display is NOT competitive with current mid-range androids

Background

This is meant to be a quick summary of the discussion surrounding high resolution displays on smartphones.

This is a touched up and more verbose version of a response on another windows phone article.

It is not meant to be comprehensive or but I'll try to expand on it if I have time in the coming days.

Limits of human vision

from cult of mac's piece why reitna isn't enough:

According to Apple’s definition, a pixel on a display must be no larger than one arc minute as seen from an average viewing distance by a person with 20/20 vision in order to qualify as Retina ... 20/20 vision doesn’t mean perfect vision ... for the iPhone 4S to have a true Retina display, it needs 65% smaller pixels.

Back in 2010, Japan’s NHK Science & Technology Research Laboratories discovered that across the board, the smaller the pixels, the more real an on-screen object seemed to the person viewing it, even if they didn’t have perfect vision. In fact, this effect is so profound on individuals that it eventually reaches a point where you have pixels small enough that on screen objects are completely indistinguishable from real objects.

What is a pixel?


Pixels are the base unit of modern graphics used to compose pictures and videos however when discussing displays, there are two types of pixels we need to distinguish between.

Logical
Logical pixels are pixels as addressed contains three bytes (thus the 0-255 limit) of information on the intensity of the three primary colours Red, Green and Blue which. When combined these three numbers tell us the colour, and brightness of one point on the display

Displayed
Displayed pixels are the pixels as they are implemented on the display. In addition to colour and brightness On LCD's and most CRT they are the same as a logical. Most AMOLED displays however, use a Pentile layout which - despite the name - only have two subpixels per logical pixel.

Pentile layouts come in two physical layouts (other than RGBG vs RGBW). The standard layout is relatively straight forward: logical pixels are displayed alternately as RG or BG with each. The diamond layout has green slightly offset vertically from the red and blue pixels. You may think of the diamond layout as the RGBG layout rotated 45 degrees. We're going to ignore that until I have time to expand on this post.

Pentilecomparison_zps39891fc4_medium

True Pixels

For convenience, we'll define a third measurement called the displayed logical pixel. This will be the measure of how many pixels are visible in practice.

There's some debate over whether a one pientile pixel should be considered as 1, 2/3 or 1/2 a logical pixel.


According to VESA, one RG/BW pair should be considered 1 logical pixel as their definitions are from the CRT era where dimensions were calculated by counting the lit/unlit line pairs.

According to critics (which ironically include samsung) one RG/BW pair should be considered 2/3rds of a logical pixel as the pixels (per line) alternate between displaying 2/3 of the colours in each line - alternating between Red and Green or Blue and Green (or White).

Another common argument is that two entire (vertical) RG/BG pairs should be considered one logical pixel as only with two display pixels a pentile RG/BG or RG/BW display is able to fully communicate the information found in one logical pixel - Red Green and Blue.
Subpixel_rendering_rg-b-gr_alternated_geometry_medium

This last argument makes the most sense in the historical context as the original pentile layouts had 5 subpixels per family - thus penta tile -> pentile. Due to the difficulties in OLED manufacturing - namely red wasnt bright enough, blue decayed too fast - the extra red was dropped and the matrix realigned to allow for wider Reds and Blues.

For the purposes of this post, we will be generous and define RG/BG or RG/BW display pixels to have a logical pixel density of 0.667 as each display pixel codes 2/3 the colour information, 2/3 the brightness information; RGB displays to have a density of 1.

Subpixel
It is because of this distinction between pixels and subpixels that when reading technical reviews of displays, we often see another specification, the subpixel. Subpixels are simply the dots that make up logical pixels.


Definitions

logical pixel density = (subpixel density)/(subpixels/pixel)

subpixel density = (subpixels/pixel) * (pixels/diagonal) / (diagonal size)


true pixel density for rgb striped displays = logical display density

true pixel density for pentile displays = 2/3 logical display density

Subpixel layouts


RG/BG and RG/BW

  • 2 dots per pixel
  • (super) amoled displays
  • NOT (super) amoled plus displays

RGB

  • 3 dots per pixel
  • some oled displays
  • almost all LCD displays

from the horse's mouth
924347253_medium_medium

Superamoledplus_medium

Rgb-stripe-vs-rgbg-vs-rgbw-pentile_medium


Data

Format


it pains me to use imperial units but I'm also too lazy to do so many conversions


Phone Name - Subpixel Layout HorizPixelsp @ Size inches

(subpixels/pixel) * (pixels/diagonal) / (diagonal size) = subpixel density

(subpixel density)/(subpixels/pixel) = logical pixel density

(subpixel density) /3 = true pixel density

Calculating pixel density (ppi) and subpixel density (dpi)

Nexus One - RG/BG 480p @ 3.7 inches
2 * sqrt(480^2 + 800^2) / 3.7 = 504.3 dpi
504.3/2 = 252.2 ppi logical
504.3/3 = 168.1 ppi true

Nexus S - RBG 480p @ 4 inches
sqrt(480^2 + 800^2) / 3 = 699.7 dpi
699.7/3 = 233.2 ppi logical
699.7/3 = 233.2 ppi true

Lumia 1020 - RG/BG 720p @ 4.5 inches
2 * sqrt(768^2 + 1280^2) / 4.7 = 663.4 dpi
663.4/2 = 331.7 ppi logical
663.4/3 = 221.1 ppi true

Galaxy S4 - RG/BG 1080p @ 5 inches
2 * sqrt(1080^2 + 1920^2) / 5 = 881.2 dpi
881.2/2 = 440.6 ppi logical
881.2/3 = 293.7 ppi true

HTC One - RGB 1080p @ 4.7 inches
3 * sqrt(1080^2 + 1920^2) / 5 = 1406.1 dpi
1406.1/ 3 = 468.7 ppi logical
1406.1/3 =468.7 ppi true

Galaxy S4 mini - RGB 540p @ 4.3 inches
3 * sqrt(540^2 + 960^2) / 4.3 = 768.5
768.5/3 = 256.2 logical ppi
768.5/3 = 256.2 true ppi

iPhone 5 - RGB 640p @ 4 inches
3 * sqrt ( 640 ^2 + 1136^2) / 4 = 977.9 dpi
966.9/3 = 326.0 ppi logical
966.9/3 = 326.0 ppi true

Analysis

Comparing pixel density (ppi)

lumia 1020 / nesus one
331.7 / 252.2 = 1.28 gain in logical and true ppi

nokia 1020 / nexus s
331.7 / 233.2 = 1.42 gain in logical ppi
221.1 / 233.2 = 0.95 or 5% loss in true ppi

galaxy s4 / lumia 1020
440.6 / 331.7 = 1.33 gain in logical and true ppi

htc one / lumia 1020
468.7 / 331.7 = 1.41 gain in logical ppi
468.7 / 233.2 = 2.01 gain in true ppi

RG/BG generational jump /generationational jump - lumia 1020 -> galaxy s4 / nexus one -> lumia 1020
1.33/1.28 = 1.04 -> 4% greater gain this generation

RGB generational jump/generational jump - lumia 1020-> htc one/ nexus s -> lumia 1020
1.41/1.42 = 0.99 -> 1% lesser gain in this generation

Comparing subpixel density (dpi)

nokia 1020 / nesus one
663.4 / 504.3 = 1.28

nokia 1020 / nexus s
663.4 / 669.7 = 0.99

galaxy s4 / nokia 1020
881.2 / 663.4 = 1.33

htc one / nokia 1020
1406.1 / 663.4 = 2.11


RG/BG generational jump/generational jump - lumia 1020 -> galaxy s4 /
nexus one -> lumia 1020
1.33/1.28 = 1.04 -> 4% greater gain relative to RG/BG displays

RGB generational jump/generational jump - lumia 1020-> htc one/ nexus s -> lumia 1020
2.11/0.99 = 2.12 -> 212% greater gain relative to RGB displays


Conclusion

Relative to previous generations

  • The effect on pixel density and subpixel density transitioning from from HD/WXGA (720p/768p) to FHD (1080p) is significant.
  • The magnitude of increase is at least as significant as the jump WVGA (480p) to HD/WXGA (720p/768p) even when accounting for the generational advances in display size.

Relative to other phones

  • The 4.5 inch 768p amoled display on the nokia lumia 1020 is rougly equivalant to the 4.8 inch 720p amoled display found on the galaxy s3

  • The display is roughly equivalent to the best of last-generation's high end offerings - galaxy nexus, galaxy s3, htc one x, et al.
  • The display is in the lower than a few of the current-generation's mid-range offerings (esp on subpixel front) even prior to release - nexus 4, galaxy s4 mini, et al.
  • The subpixel density has regressed generationally from the lumia 920 due to the switch from lcd to amoled subpixel arrangement

Screen-comparison-galaxy-s4_medium
full res

Relative to human vision

  • The HTC One's RGB display is near the limits of the human eye with respect to detail but not gamut or granularity.
  • A further 40% increase in pixel density for RG/BG or RG/BW displays is needed to reach the current detail of current-generation RGB displays.
  • A further 40% increase in pixel density for RGB displays will mostly be lost outside of serving to decrease the colour granularity of pixels as seen by the eye.
  • Next generation screens should focus heavily on improving colour reproduction (gamut) and operational contrast (max/min brightness in environment) and less on raw pixel density.

Aside: Regarding Nokia's Windows Phone exclusivity

Given:

  • Windows Phone's current display limitation, chipset (and therefore CPU/GPU) support, application availability, and Microsoft's glacial development speed
  • Nokia netted Microsoft 500 million in the Windows Phone deal
  • WP 8.1 is likely to still lag behind Android 4.2 feature wise
  • Nokia's success is now entirely dependant on the success of Windows Phone as a platform
  • Windows Phone as a platform relies heavily but is not necessarily dependant on the success of Nokia
  • These and the CE/NT kernel limitation was easily predictable (even obvious) at the time of the deal.

Elop's Windows Phone deal was a poorly researched and overly decisive at best; made in the interests of Microsoft not Nokia at worst.

Microsoft is limiting Nokia's ability to offer competitive SOC's and Displays.


tl;dr - nokia 1020 display is worse than 920; other than the camera, nokia flagships are generationally behind

History:


Update 0 - fixed spelling mistakes, redundant paragraphs
Update 1 - improved background section
Update 2 - working on true logical pixels
Update 3 - 13/7/15 - improved clarity, removed owl gif