Distance of a viewer from a screen or picture. If viewers are too far away they will not be able to see the full detail of the images; if too near they will see the limitations of the detail in the images and possibly not see the picture’s edges. The ideal viewing distance, where you clearly see all the available detail, depends on the size of the video image, SD, HD, etc, and the size of the screen.
There is a rule-of-thumb to work out the ideal viewing distance, where you can see all the detail – provided you have a matching HD or 4K (or maybe 8K) capable screen. This is calculated by taking into account the acuity of the human eye, which is about one second of arc (1/60 of a degree). This means to see all the detail of SD television pictures on a 16 x 9 screen, we need to be no more than 6 screen heights (H) away. 1080-line HD slightly more than doubles the horizontal and vertical detail so we need to half the distance to 3H to see all that HD is offering. With 4K (twice the HD vertical and horizontal lines and pixels) we need to halve the distance again – to 1.5H. And if you are looking at 8K, it’s just 0.75H. If you don’t want to get so close to the screen the other way around is to get much a bigger one that is able to display all the pixels of your biggest chosen format.
Fortunately TV screen manufacturers have risen to the challenge… or have they? If viewing 1920 x 1080 HD on a 40-inch screen a viewer would have to sit no more than 60 inches (1.5m) away to see all the detail. For 4K UHD that should be reduced to 30 inches (0.72m). Then for 8K the distance would be just 15 inches (38cm). Perhaps that feels too close, so the alternative is to have a bigger screen. Assuming viewing at 1.5m is comfortable, then 4K viewing would require an 80-inch screen and for 8K, the rarely observed 160-inch screen!
The same principals apply in other digital viewing environments, such as cinema. Typically to appreciate all the detail of the DCI 4K (4096 x 2160) pictures, you would probably have to be in the front third of the cinema. For 8K (not a DCI standard), keep in the front few rows.
With this in mind, the design and shooting of scenes should allow the audience to see a great deal of detail, and have most, if not all, of their vision filled with the screen’s images. This has implications for scenery, make-up and wardrobe as well as lighting.