Saturday, 5 December 2015

TVs–What type screen size and resolution…. OR… Why we won’t be buying a 4K TV!

Slightly nerdy post


I recommend you don’t buy one of those new 4K TVs unless it will have at least a 95” screen and you will be sitting more than 12ft from it.

The Main Story

Whilst wandering around a local Currys PC World shop I happened to notice the new 4K and OLED TV’s.  At some future date we will need a new TV so I started investigating.  When considering TV’s there are three main factors. 

  • The type of screen (eg, plasma, LCD, LED [edge or backlit] and OLED)
  • Screen size measured diagonally in inches)
  • The resolution (the number of pixels (dots) the screen can display

I’m going to give my reasons why we won’t be buying one of the latest 4K television sets.


Plasma.  These screens are now almost obsolete.  They produce a great picture but are energy intensive, heavy and expensive to make. (no longer made)

LCD. (liquid crystal display).  Commonly used in computer screens and some cheaper TVs. LCD crystals do not produce their own light, so an external light source like a florescent bulb is needed to create an image. (old technology)

LED (light emitting diode).  This is an updated version of the LCD but instead of a florescent bulb the display is either backlit or edge lit by LEDs. (majority of TVs use this type of screen)

OLED (Organic Light Emitting Diode). A completely new technology which uses ‘organic’ materials like carbon to create light when supplied directly by an electric current. Unlike LED/LCD screens, an OLED TV doesn’t require a backlight to illuminate the set area. Without this restriction of an external light source, OLED screens can be super thin and crucially, flexible.  OLED screen provide ‘true’ blacks good contrast, and very little motion blur.


You can buy a screen anywhere from 12 to 100 inches.  The important factor is ensuring the screen is neither too small or two big.  If it’s too small then you can’t see the detail on the screen.  If it is too big you have a similar problem.  A rough rule is 

DISTANCE from TV (in inches) ÷  1.5 = TV SIZE (in Inches).

The factor of 1.5 in the above equation has gradually been reducing over the last decade because TV screen resolution has steadily improved.

SCREEN RESOLUTION (the number of dots)

That old cathode ray tube had a resolution of 520 × 576 which equated to ~299,520 pixels (dots) on the screen.  As a boy I’m certain if I got up close to the screen I could count them .  The picture looked “grainy”.  There will always be the same number of pixels whether the screen is large or small.

Along came Digital TV and the resolution increased to 720 × 576 or 414,720 pixels.  This is DVD quality.

Then High Definition TV appeared (1280 × 720) or 921,600 pixels which was almost 3 times the quality of that cathode ray tube TV)

Blue Ray arrived (1920 × 1080 or 2,073,600 pixels)

Today there are 4K TV’s (3840 × 2160 or 8,294,400 pixels)

The 8K screens are currently being developed.

Increasing the screen resolution has resulted in better picture quality.  But the human eye is an analogue viewing device.  It can only absorb a finite number of dots.  Imagine you have sprinkled a thin layer of sand over a baking tray.  Hold it up to your chin and count the grains of sand.  If you have young eyes you can probably see all of them.  Now place the tray at your feet and count the grains.  Then imagine placing the tray where the TV is and count them.  You might see some of the grain with the tray at your feet but unless you have exceptional vision you wouldn’t see any of them when the tray is placed where the TV is.  The fact is your eyes reach a saturation point and the number of dots becomes irrelevant to the quality of the image.  you can see too few dots (grainy image) but you can’t see too many dots.

One of the factors that dictates the maximum size of your screen is the size of the room.  Put a big screen in a small room and you’re likely to be sitting on top of it.  Your eyes then can’t take in all the detail.  Put a small TV in a big room and it’s too far away to see the detail.  What’s the optimum size screen for your room?  This next diagram gives an indication of the most effective screen size based on your distance from the TV and it’s resolution. 



Consider you are sitting 8 feet from the TV. 

If your screen is up to 40” then you only need a standard high definition TV.  Any higher resolution is a waste because your eyes can’t see the additional pixels.

If you opted for a 40” to 60” TV then a 1080p (Blue Ray quality) TV is the highest you need.

At 8 feet from the screen it isn’t until your TV screen is larger than 65” that you need to consider a 4K TV.  Go back to our distance formula (8ft x 12in = 96” ÷ 1.5 = 64” max size screen)

Whilst travelling around the UK I’ve noticed the average home TV room is smaller than a similar room in Australia.  A 42 inch TV is probably the norm.  In Australia you might be 12 feet from the screen.  At that distance you don’t need a 4K screen unless it’s 95” or greater.

Why 4K

So why the big push to sell 4K.  I think it’s sales hype… the industry can’t justify selling you the same old TVs, they need a gimmick to retain market share.   Amusingly there currently isn’t much 4K content to watch and it’s going to take some time before 4K content is readily available.  Those 4K TV’s in the shop are showing short custom produced clips. 

Netflix is streaming some 4K content over the internet (if you have a good enough internet data allowance and can afford it). How many people upgraded their DVD collection by purchasing the same films in Blue Ray.  If you’re like me you just kept your DVD’s.  So how many people will upgrade their home media library from blue-Ray to 4K?  No doubt the media companies will be encouraging this.  The size of 4K media actually creates another problem.  A DVD can store approximately 4.2Gb of data and a Blue-Ray disk stores approximately 30Gb of data.  4K is four times larger than Blue-Ray (30x4=120Gb).  There isn’t a commonly available portable storage medium (apart from SSD’s and hard drives) that can hold that much data. 

Obviously the industry is aware of the sheer volume of data involved in broadcasting 4K.  A new codec (H.265) has been developed to compress 4K by a factor of six (6).  This means a 4K film can be compressed to approximately 20Gb.  But this raises two other issues.  How many people will be prepared to use 20Gb of their internet data allowance to stream a 4k film?  Also, the 4K TV will need to have a inbuilt computer with sufficient power to decompress the streamed data.  When considering purchasing a 4K TV it will be essential it has H.265 capably.


OLED technology produces a better quality picture than the current LED screens.  The resolution isn’t a factor. If you want a picture with sharp edges and true colours (especially blacks and contrast) then OLED is a better choice.  But OLED is the “new” technology and is currently expensive.  All large (over 40”) OLED TVs will probably have 4K resolution, but they will produce a better picture than a straight 4K TV.  

If you are currently looking for a new TV then my suggestion would be to look at 1080p (High Definition) TV’s.  The main manufacturers are no longer making them and the prices are dropping rapidly.   I intend to ignore 4K (like the tide… you can’t stop it) and closely watch the price of OLED.


Daykin said...

Panasonic Plasma 42in big enough I feel.

Tom and Jan said...

Plasma TV technology is good but it is energy hungry and can suffer from burn-in!

Catherine VK4GH said...

I love your nerdy posts, I always learn something.

Tom and Jan said...

Don't you feel lonely being the only one! :-)

Dave said...

Not that you would :) but i suspect you read this article before writing yours

I think 4K is being pushed like 3d was two years ago. Everyone has upgraded to flatscreen HD tvs and the manufacturers and stores need something to persuade people to upgrade again.

However until the tv cpu is powerful enough to process all the signal along with everything else (see how long it takes to load up iplayer or similar) without lag or stuttering, i won't be buying.
Then as you said there is the lack of 4K content and how its delivered. Luckily i live in a cable tv area so can get fast unlimited broadband but the cable tv box can't do 4k and only just copes with HD, again its cpu just doesn't have enough grunt - its all built down to a price.

I suspect there will be a lot of unhappy buyers once they realise that their cheap 4K tv is very slow due to cheap low powered cpu, or that their cable/satellite/broadband can't do 4k (and maybe never will).

As you say though, it you need a new tv to replace a faulty one, go for OLED in HD and then save your cash since in 5 years 4K will be down to HD prices and hopefully there will be content to play.

Tom and Jan said...

Hi Dave,

I hadn't seen that particular website but it's good to know I'm not alone!
My feeling is 3D TV is dead and curve will be very shortly.