The whole concept behind correct TV viewing is that of enjoying the best seat, yet few are aware of what are the requirements to meet this objective. Most of the information on the Internet just points to the fact that the optimum TV viewing distance depends on the screen size of the TV.
Unfortunately, this is just part of the story and will not always lead to the best results. There is also the issue of image resolution as well as whether you are watching 2D or 3D content.
Equally important is that the TV size — or projected image size in the case of a front projection setup — will also determine the maximum number of seats in a multiple-row seating arrangement if one want sot ensure that all viewers enjoy a truly immersive experience.
Optimum Viewing Distance for the best TV viewing experience
Sony BRAVIA KDL55HX850 55-Inch
Many home theater owners are tempted to go for the biggest screen size they can afford when buying a big screen TV for their home entertainment. Others simply go for a TV size they think is big enough simply because it is bigger than their older TV!
Yet, there are more important considerations that come into play when choosing your TV size…
Is the TV screen size big enough for your viewing distance and seating capacity?
If budget is an issue, should you opt instead for a lower-spec model in favor of a bigger TV?
If you are after a truly immersive TV viewing experience, you cannot just pick the TV size you want since the optimum size for your TV is primarily dependent on the available viewing area.
And as we will show, there are more factors that one has to consideration in this TV viewing distance – screen size equation. But do not worry!
We simplify the whole process for you by presenting a few basic principles you can follow to determine the best screen size for your room as applicable to 2D TV viewing. We specify here the issue of 2D as with 3D TV viewing, things are slightly different due to other constraints come into play. We discuss the subject of 3D TV viewing in our article ‘3D Viewing Distance Explained‘ appearing under the 3D TV section of the site. It analyzes the principles as derived in this TV guide but applied within the limitations imposed by what is known as the 3D TV comfort zone.
TV Viewing Distance: Some say it is just a question of sitting wherever you like, but is it really so?
Some prefer a close encounter! Yet, try to sit a bit too close and you risk seeing not only more of the image artifacts but also the image pixel build-up structure; the result is distracting, one that will spoil your viewing. Others prefer to sit farther away but… sit a bit too far and you may forget about an enjoyable immersive movie experience.
Surely, there are different opinions on what constitutes the best TV viewing distance. Personal preferences play a big role here; just visit the movie theater and see how some will sit at the back while others choose one of the front rows for a wider viewing angle; and then you will also find those that will choose a seat randomly.
There is no arguing about personal preferences in that here we are not dealing about some scientific rules, yet there are still a number of important practical guidelines worth following in any home entertainment setup.
SMPTE and THX
SMPTE (Society of Motion Pictures and Television Engineers) recommends making use of a screen size that fills a minimum of 30 degrees field of view at the seating position. This implies that for best results, the viewing distance in a home theater setup should be set such that the extreme ends of the width of the screen constitutes a minimum angle of 30 degrees at the viewer position; this corresponds to a TV viewing distance that is 1.87 times the screen width.
This 30-degree viewing angle is accepted as the basics in any home theater room design.
The THX certification standard specifies a range rather than just a minimum angle. THX requires the row of seats at the back constitutes a viewing angle of at least 26 degrees while the nearest seating position should correspond to an angle of view that is no more than 36 degrees; within these limits, the viewer will enjoy a more immersive viewing experience.
These subtended angles correspond to a TV viewing distance that varies between 2.17 and 1.54 times the screen width.
Visual Acuity: What about your vision limitations?
Many just stop at relating the TV size with the viewing distance. In this respect, both SMPTE and THX specify a viewing angle – or a viewing range in the case of THX – that yields a good seat.
But how does correct TV placement relates to the viewer’s vision system, more specifically, how does TV viewing distance relates to a person’s visual acuity?
The issue with visual acuity does not deal with identifying the best viewing position for your screen size; rather, this dictates the maximum distance beyond which one will not be able to see all picture detail as a result of the limitations of one’s eyesight.
Visual acuity is by definition, a measure of the eye spatial resolving power; it specifies the ‘angular size’ of the smallest detail one’s eyesight can resolve.
A person with normal vision – often referred to as 20/20 (or 6/6 when expressed in meters), can resolve a spatial pattern where each element within the pattern subtends an angle of one minute of arc angle at the eye (i.e. 1/60th of a degree) when viewed at 20 feet, or 6 meters away. This represents the minimum angle of resolution (MAR). This means that a person with normal can see an object with a height of 1.77mm at 20 feet way.
From a TV viewing distance perspective, visual acuity represents the distance beyond which some of the picture detail will no longer be resolved by one’s vision system, as it will appear to blend with adjacent picture information. In practice, this implies that the smallest element comprising the image – the pixel – should have a size that is not smaller than 0.0698-inch when viewed from 20 feet away.
Translating visual acuity limitations in terms of minimum image size when viewing takes places from 20 feet away would give:
For NTSC standard definition TV, minimum image width is 640 x 0.0698″, or approximately 45-inch. This gives a maximum viewing distance that is 5.37 times the screen width.
Similarly, for HDTV, this gives a minimum image size of 89-inch for 720p HDTV (1280 x 720 pixel image) and 134-inch for 1080i and 1080p HDTV (1920 x 1080 pixel image.) In terms of screen width, these image sizes correspond to a maximum TV viewing distance that is 2.7 times for 720p, and 1.8 times the screen width for 1080p HDTV.
In other words, you would not be able to enjoy the full benefits from the higher pixel count associated with a 1080p HDTV if you were to sit further away than 1.8 times the TV screen width from your HDTV. This means that if you were to increase the TV viewing distance to 2.7 times the screen width, the picture detail from a 1080p HDTV will appear just the same as that from a cheaper 720p HDTV of the same screen size!
What does this mean in practice?
We have already hinted on a simple way of relating viewing distance to screen size as resulting from SMPTE/THX recommendations and visual acuity limitations.
To make things easier, we have come up with a rule-of-thumb based on the above guidelines. This guiding principle for TV viewing distance refers to the width of the screen rather than the more common screen diagonal measurement since all is related to the subtended viewing angle in the horizontal plan. Furthermore, referring to the screen width has a further advantage – namely that it applies to any screen irrespective of its aspect ratio, whether that being 16:9 or 4:3.
For optimum TV viewing distance, the nearest seating position should be limited to two times the screen width; the furthest seating position should be at maximum, five times the screen width.
This yields a good approximation for an optimum TV viewing distance, but it does not necessarily represent the best viewing distance in a home theater setup. Rather, this rule represents the theoretical range within which viewing distance is out of the trouble zone. Sit closer than two times the screen width, and pixel breakup and video artifacts will become too visibly intrusive; move further away than the maximum recommended distance and you will not see the full picture detail.
Keep in mind that…
These minimum and maximum TV viewing distance limitations are dependent on the image pixel resolution, or rather on the video signal definition. A fully resolved 1080i or 1080p HD signal supports closer viewing than standard television. Thus…
While 1.5 to 2 times the screen width represents the optimum TV viewing distance for a 1080p HDTV, it is too close when viewing standard definition content, even if that content is viewed on an HDTV. In the case of standard definition, sitting at more 3 times the screen width represents a better seating option as the closest viewing distance.
The same applies for the 5 times the screen width for the maximum viewing distance; though this is adequate with standard definition video, it is too far from the screen for a person to view the fine detail supported by higher pixel count of HDTVs. Thus, when it comes to 720p and even more so 1080p HD content, three times the width of the screen represents a more practical option as the maximum TV viewing distance.
Note: Our rule-of-thumb for minimum and maximum TV viewing distance applies irrespective of the screen size, yet it works best with screen sizes exceeding the 40-inch diagonal.
Anything smaller than this, is too small to qualify as a big screen home theater option. At the smaller screen sizes, even if one were to stay in line with the best viewing distance as recommended by SMPTE or THX, it would still be difficult to get a truly immersive viewing experience.
Maths not for you? No problem!
The following table gives the recommended minimum and maximum viewing distance for different 1080p HDTV screen sizes:
Optimum Viewing: Vertical Angle and Screen Height
There is more to optimum viewing than just a consideration based on the TV viewing distance. For a most comfortable viewing experience, optimum viewing would result when the viewer’s eyes are level with the center of the screen.
We all know this is not always possible, especially in the case of big projections in the home theater. SMPTE recommendations to keep the maximum vertical angle as measured from eye height of a seated viewer at the front row center seat to the topmost part of the TV screen (or projected image), should not exceed 35 degrees. This is NOT the optimum vertical viewing angle; it is the limit beyond which the viewer is subject to excessive strain on the neck.
In as much as we speak about a maximum vertical angle, there is also a minimum vertical angle; in this case, this represents the minimum field of view in the vertical plane necessary to help fill the viewer’s view to create a more immersive viewing experience. There are no guidelines here from SMPTE or THX, but studies show that if the screen height occupies less than 15 degrees of the viewer’s field of view in the vertical plane, the image would appear too small for an immersive experience.
A Few Practical Points to Consider
If you were to mount your screen at the correct height, it is unlikely you will have to worry about the maximum or minimum vertical viewing angles in a typical home theater installation. Keeping your TV viewing distance within the limitations detailed above would automatically imply compliance with both the minimum vertical angle of vision and the maximum vertical angle.
In other words, the fixed relationship as determined by the TV screen or projected image aspect ratio for the screen height and width, simplifies this whole issue. Remember however – you have to stay within the minimum TV viewing distance detailed in our calculations, i.e. no more close than 1.54 to 2 times the screen width, otherwise the viewer will be subject to excessive strain on the neck.
However… If you were to wall mount an LCD or plasma over the fireplace and sit too close to the TV screen, there is a real risk of approaching the recommended 35 degrees maximum vertical angle of view, thus subjecting the viewer to increased neck strain.
TV Viewing Distance and Multiple-Row Theater Seating
This discussion on TV viewing distance would not be complete without explaining how the conclusions we have arrived at, applies to multiple-row seating in the home theater.
As indicated earlier on in this discussion, THX recommends a viewing angle ranging from 36 deg. maximum to 26 deg. minimum; within this range, every seat can be considered — theoretically — as a good seat. However, whether one can really sit at such a close TV viewing distance resulting in a field of view of 36 deg. depends on the quality of the video content and the pixel screen resolution.
Multiple-row seating in the home theater and Screen Size
The maximum number of rows in a home theater depends not only on the floor area, but also on the screen size, or rather the relative size of the screen width, with respect to the size of the theater seats.
Just to clarify further: Assume you are using standard home theater seating; you will need approximately 44-inches per row. A 16:9 screen with a width of 100-inch would easily accommodate a third row while remaining within the 36-26 deg. range limit defined by THX.
However, simple calculations show that if you were to move to a smaller screen having a 65-inch width (75-inch diagonal for a 16:9 screen), you would not be able to fit in a third row.
Rule of thumb: Divide the screen width in inches by 30 and then round off to the nearest integer. The result will correspond to the maximum number of rows afforded by your screen size; this applies for standard size theater seating.