Optimum HDTV viewing distance

[1] The "thrilling realism"[2] HDTV attempts to offer arises from increased resolution (detail) and the typically large screen sizes.

While helping to define the HDTV standard, RCA engineer and member of the US delegation to the International Telecommunication Union-Radiocommunication Sector (ITU-R), Bernard J. Lechner, made an early analysis of viewing distance, deriving the so-called Lechner distance.

This is the "optimal viewing distance" found in the ITU-R.[5] The concept of presence has been described as the sensation of "reality", of "being there", and as "an illusion of non mediation".

[6][7] The optimum viewing distance is affected by the horizontal angle of the camera capturing the image.

A mismatch in this regard is traditionally disregarded, but some rotating motions can make these distortions very noticeable as a pincushion effect.

Conversely, a longer focal length (telephoto) lens captures a narrower angle of view, demanding a more distant viewer position.

Such opposing viewing distances would not only be impractical, but would negate the very purposes of telephoto shots (for example, to see a distant object in more detail, or minimize distortion in facial images) and wide-angle shots (causing the viewer to sit too close to the screen, where undesirable image artifacts would be visible).

[6] More importantly, the wider the visual angle (up to a plateau at approximately 80 degrees), the greater the feeling of presence.

For the most part, the majority of the fixed distance recommendations were issued before the end of 2007, when arguably HDTV displays were still in the early adoption phase.

[12][13] The concept of optimal viewing distance,[5] which is based on physics and physiology, has become essential with the advent of UHD (Ultra High Definition) technology.

The "optimal viewing distance"[5] is based on the limits of the human eye, i.e. its angle of resolution.

[15] One of the more popular recommendations on the proper HDTV viewing distance is multiply the diagonal measurement of the display screen by 2.5.

This recommendation is cited by television manufacturers,[16] retailers,[17] respected publications[18][19] and websites,[20] though the popular electronics review website CNET suggests that high-resolution content can be watched at a closer distance – 1.5 times the display screen's diagonal measurement (corresponding to 32 degree viewing angle).

[27] Their recommendation was originally presented at the 2006 CES show, and was stated as being the theoretical maximum horizontal view angle, based on average human vision.

Early adopters of HDTV were typically videophiles,[29] the technically adventurous[30] and the sports enthusiast[31] looking to have the ultimate viewing experience.

Today, the typical HDTV consumer's aims may be a little more modest; total immersion takes a back seat to room integration.

[41] Crutchfield's maximum viewing distance aligns with the lower boundaries where viewers typically begin to find HDTV immersive.

In the absence of economic influences, calculating the best screen-size-to-distance ratio that will produce the utmost feeling of presence is not at all straightforward.

There are a number of factors that can affect the calculation including the limitations of the human visual system,[8] the technological limitations of HDTV displays,[11] human physiological considerations,[8] the content that will be viewed,[6] and the interpretation of empirical data from formal testing.

Our understanding of limitations with regard to visual detail recognition and identification from a distance is primarily based on the work of Dr. Hermann Snellen.

From his findings and the work of others over the last hundred years, one arcminute is seen as the threshold beyond which critical detail cannot be identified[43] by a person with normal vision.

[46][47] The visual acuity threshold has been identified as a constraint factor in the recommendations on the optimum viewing distance for HDTV,[38] and also in formal research that comment on the subject of television and angular resolution.

[41] With 30 arc seconds as the constraint, the view angle necessary to see all the detail provided by an HDTV with a 1080p resolution drops to approximately 16.1 degrees.

Like computer monitors, each HDTV display has a video resolution consisting of rows and columns of specific numbers of pixels.

[11] The image then loses its smoothness, its perceived quality drops, and the advantage of closer viewing becomes a disadvantage.

But pixel geometry varies as well, in shape and spacing (known as interpixel gap[38]), depending on a display's technology and design.

Subjects have reported experiencing an increase in symptoms that are common to motion sickness when viewing strong visual stimuli on large screens.

[8] A study conducted using virtual reality simulation as part of the experiment, found that subjects with lower visual acuity experienced significantly more of the symptoms associated with motion sickness.

Furthermore, the study also found that the symptoms of motion sickness increased when subjects observed the visual stimuli without the aid of their glass or contact lenses.

Viewers with lower visual acuity, who prefer to watch HDTV without their corrective lenses may want to sit closer to see critical details and run the risk of undesirable side effects.