YOUR EYES
One minute of arc
ITU-R BT.1845 takes the typical limit of human vision as 1 arc-minute. Optometry teaching says 6/6 vision resolves about the same, a sixtieth of a degree.
See the numbers
WHAT THE STANDARDS SAY
Sharper only
if you sit closer.
More pixels only help if your eyes can see them.
International broadcasting guidance works out an optimal viewing distance for each picture format, based on how finely the human eye can see. The more pixels, the closer you need to sit to take in all the detail.
1 ARC-MIN the eye's typical limit
Pick a format- Acuity sets the limit
- Distance decides the gain
- Contrast matters too
- From the sofa to the screen
THE SHORT ANSWER
It depends on
where you sit.
Resolution, screen size and distance work together.
The ITU expresses distance in picture heights, written H.
THE DISTANCE
Half the distance for 4K
The ITU's optimal distance is 3.2 picture heights for 1080p HD and 1.6 for 4K. Sit further back than that and the extra detail gets harder to see.
Pick a format
THE CONTRAST
Brighter, not just sharper
High dynamic range widens the gap between black and white. The BBC and NHK developed the Hybrid Log-Gamma HDR system, now part of ITU-R BT.2100.
About HDR
FOUR STEPS TO TRY
Measure first,
upgrade second.
You can apply the ITU's picture-height figures to your own room with a tape measure.
Measure the picture height
Measure the height of the picture area on your screen, top to bottom, not the diagonal.
Measure your seat
Measure from your usual seat to the screen, and divide by the picture height to get your distance in H.
Compare with the table
About 3.2 H suits 1080p, 1.6 H suits 4K and 0.8 H suits 8K. Further back, the extra pixels matter less.
Do not forget contrast
Brightness and dynamic range change how real a picture looks, separately from how many pixels it has.
TWO NUMBERS WORTH KNOWING
Fine detail has
a viewing distance.
One figure on how finely we see,
one on how close 4K asks you to sit.
1 arc-minute
Typical smallest detail the eye can resolve
The ITU takes the optimal viewing distance as the point where two adjacent pixels subtend 1 arc-minute at the eye. University of Sydney teaching notes give the resolution limit as between 30 seconds and 1 minute of arc.
VISUAL ACUITY · ITU-R BT.1845
1.6 H
Optimal viewing distance for 4K UHD, in picture heights
For 1080p HD the figure is 3.2 H, and for 8K it is 0.8 H. Each step up in resolution halves the distance at which you see all the detail.
4K DISTANCE · ITU-R BT.1845
The same Recommendation takes the closest comfortable viewing distance as 25 cm and normal reading distance as about 35 cm, which matters for phones and other small screens.
A QUICK FORMAT CHECK
How close
should you sit?
Pick a picture format to see the ITU's optimal viewing distance, measured in picture heights (H). The bar shows how close you need to sit to see all of its detail.
From Recommendation ITU-R BT.1845-1, Table 1. One picture height is the height of the picture on screen, not its diagonal.
ABOUT HDR
More range,
not more pixels.
BBC Research and Development describes HDR as increasing the difference between black and white in video, so that water glistens and sunlight looks golden while detail stays in the shadows.
Hybrid Log-Gamma was designed to work without metadata and to be compatible with standard dynamic range television in the same colour format. It is included in ITU-R BT.2100, the international standard for HDR production, and is royalty-free.
Questions
Questions people ask
Can I see the difference between 1080p and 4K?
It depends on your distance. The ITU's optimal viewing distance is 3.2 picture heights for 1080p and 1.6 for 4K. At the 1080p distance or further, the extra 4K detail becomes harder to see.
What does 'picture height' mean?
It is the height of the picture on the screen. The ITU expresses viewing distance as multiples of it, written H, so the figures work for any screen size.
What is 1 arc-minute?
A sixtieth of a degree. The ITU takes it as the typical limit of human visual acuity, and optometry teaching says 6/6 vision resolves about 1 minute of arc.
Is 8K worth it?
The ITU's optimal viewing distance for 8K is 0.8 picture heights, which means sitting closer to the screen than the picture is tall to see all of its detail.
What is HDR?
High dynamic range increases the difference between black and white in video. One HDR system, Hybrid Log-Gamma, was developed by the BBC and NHK and is part of ITU-R BT.2100.
Sources
- Recommendation ITU-R BT.1845-1: Guidelines on metrics for image quality levels, display sizes and aspect ratios
- BBC Research and Development: High Dynamic Range television and Hybrid Log-Gamma
- University of Sydney, Save Sight Institute: Visual acuity measurement
- Webvision: Visual acuity
Updated