OPINION: ON THE AGENDA 13
Type of display 17in computer
2.5m computer SXGA+
projected image 10m cinema
1:85:1 projected image 2K 10m cinema
1.85:1 projected image 4K
The table shows minimum viewing distances, based on the ‘one minute’ rule for various kinds of displays *In practice these distances may be halved
Pixel pitch Theoretical minimum viewing distance Practical minimum viewing distance 1.9mm 6.5m 2.5mm 8.6m 4.0mm 13.7m 6.0mm 20.6m
2-3m 3-4m 4-6m
6-10m A guide to viewing distances for LED displays
there are many applications involving close viewing and/or high information content where users require a shorter viewing distance. Here ‘4K’ (or in practice UHD, 3840 pixels wide) comes in to play, with both greater information content
and half the viewing distance (1.8m) without visible pixels. While 4K LCDs are more expensive than 2K
displays of the same size, the price differential will quickly narrow, for two reasons. Not only
Display width Horizontal pixels Approx pixel size Minimum viewing* 335mm
30in medical display 654mm 50inch HDTV
2.5m 10m 10m 1106mm
1400 3280 1920
1400 1998 3996
0.24mm 0.2mm
0.57mm 1.8mm 5mm 2.5mm 0.8m
0.68m 1.96m
6.1m 17m 8.6m
are manufacturers turning out 4K panels at a fantastic rate, but they have perfected their processes to the extent that changing from 2K to 4K can be likened to changing a font size in printing.
High-brightness LED displays have primarily been associated with sports grounds and similar venues. However the emergence of high- resolution displays with pixel pitches down to 1.5mm (with lower coming) is opening up a lot of new applications. The most exciting applications are in architectural schemes where the displays become part of the environment instead of being ‘tacked on’. A good example here is the Tom Bradley Terminal at Los Angeles Airport (LAX) – the spaces are big enough that 6mm pitch LED is fine. However the fine-pitch products are likely to find application in traditional markets – it is significant that at InfoComm 2014 both eyevis and Leyard were showing LED videowalls in control room applications. In conclusion, users can have images of any
size they want, but quite apart from the demands of the image content, the pixel size rule must be followed to avoid visible pixels.
Robert Simpson is founder director of Electrosonic.
August 2014
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