3D TV Viewing Distance Guide
for an immersive 3D experience
How does 3D TV viewing distance, screen size, and viewing angle
relate to an immersive and realistic 3D experience?
There is more to a great 3D TV experience than just one of the latest 3D HDTVs, a 3D-enabled Blu ray player, and access to one of the emerging 3D TV content providers. You need to watch out closely on your 3D TV viewing distance to enjoy the third dimension.
Not only, your 3D TV screen size and TV viewing angle with respect to your seating position also play important roles in delivering a realistic 3D experience.
In this 3D TV guide, we discuss the correct TV placement―or rather the optimum seating position―for an immersive 3D viewing experience. In the process, we also see how this viewing distance relates to the TV screen size, the screen resolution, and your viewing angle with respect to the screen.
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What constitutes an optimum TV viewing distance for 2D does not necessarily leads to an optimum 3D TV viewing experience in the home.
As we have stated in our 2D TV Viewing Distance guide, when it comes to standard TV viewing, the factors that come into play to determine the optimum viewing distance for an immersive 2D experience, relate only to the TV screen size and the screen resolution.
As we will further explain in this 3D TV viewing distance guide, with 3D, things start to get a little bit more complicated, and to a certain extent, even more demanding on the user to enjoy a truly realistic viewing experience. Fail to achieve a realistic 3D viewing experience and your 3D viewing at home starts to be tiring on your brain; it can even makes you feel sick! Fail to achieve an immersive and enjoyable 3D experience, and you will never manage to view a 2-hour 3D movie at home. Why is this so?
In the case of 3D TV, one cannot determine the optimum 3D TV viewing distance simply by relating the latter to the screen size and the TV screen resolution. One has to keep in mind that the illusion of a third dimension in 3D TV causes the nearest point of the 3D image to appear closer to the viewer than the TV screen itself.
Similarly, the farthest point of a 3D TV image appears farther away from the TV screen, this despite that the TV image is actually being displayed on a flat surface at a fixed distance away from the viewer.
Here, a third factor comes into play that imposes its own constraints on the whole 3D TV viewing distance equation. This is what is referred to in 3D TV technology as the 3D comfort zone.
As further explained in our article '3D TV Technology and the Human Vision', there is a disparity in 3D TV―known as fundamental disparity―between the eyes convergence point and the eyes focusing point. This disparity is totally unnatural for the brain since in the case of a real 3-dimensional object, these two points reside at the same point in space.
This disparity between convergence and focusing, increases as one moves closer to the 3D TV screen to enjoy to a more aggressive 3D experience. Move further away and you will start losing more of the desired 3D impact.
Fundamental disparity in 3D TV technology is directly related to the image parallax, i.e. to the separation between the left eye image and the right eye image. The value of the image parallax determines the aggressiveness of the 3D viewing experience.
The audience 3D comfort zone refers to that parallax range which results in a 3D viewing experience that is easy on the viewer. Exceed this comfort zone and the brain would start finding it hard if not impossible to properly fuse the left and right eye images into one virtual 3D image. Should this happen, the 3D image would eventually appear as a blurred 2D-image. In some individuals, this may result in disorientation and even headaches.
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What is the optimal 3D TV viewing distance subject to the constraints associated with the 3D TV comfort zone? How does this impacts screen size and screen resolution?
2D TV Viewing Distance Limitations
In our 2D TV viewing distance guide, we stated that THX recommends maintaining the field of view between 26 degrees and 36 degrees for an immersive TV viewing experience. We have also shown how this translates to an optimum TV viewing distance that varies between 2.2 to 1.54 times the screen width for a 16:9 display.
We have also explained that how close you can sit to the TV screen depends on the screen resolution. The constraints resulting from visual acuity imply that the maximum viewing distance to enjoy every single bit of detail in the image should be limited to 1.8 times the screen width in the case of a 1080p HDTV and 2.7 times in the case of a 720p HDTV. Movie farther away and you would not be able to see the full picture detail supported by the respective screen resolution. Watch your HDTV from a distance corresponding to 3.5 to 5 times the screen width and your HDTV image would soon start appearing the same as if it were being displayed by standard definition TV!
Now, move closer to the TV screen than these recommended viewing distances and you risk seeing the image buildup structure, with the image taking a somewhat blocky or pixilated appearance. At these closer viewing distances, image artifacts also become more visible; this may eventually ruin an otherwise pleasing viewing experience.
Before delving further with our 3D TV viewing distance discussion, it is important to realize that unlike in the case of 2D, your 3D TV viewing distance is less a matter of personal preference. The constraints resulting from the 3D TV comfort zone, imposes strict limitations as to where you can sit to enjoy 3D television. In this respect, the recommendations detailed in this article should help you find that sweet spot for a more enjoyable and realistic 3D TV viewing experience.
To be able to arrive at the optimal 3D TV viewing distance, we need to determine how the limitations associated with 2D TV viewing fits within the constraint associated with the image parallax comfort zone in 3D TV.
In our article 'Challenges of 3D TV in the Home', we referred to a study by In-Three Inc. which shows that the comfortable parallax zone in 3D TV for a person with an interpupillary distance of 2.5 inches, is just 2-inches when the viewer is sitting 6 ft away from a 60-inch screen. This reduced comfortable parallax range corresponds to a virtual 3D image whose nearest point stands at 1.8ft in front of the screen while the farthest point is at 4ft behind the screen, or 10ft away from the viewer (ref. to the diagram below).
Image courtesy: David Seigle and John Sanders, In-Three, Inc
The same study shows that the parallax range for comfortable 3D viewing in the movie theater for a viewer sitting 40ft away from the screen is 12.5 inches; this leads to a virtual 3D image whose closest point is 8ft away from the viewer while the farthest point resides at infinity!
The reduced parallax range in the case of 3D TV viewing is necessary as objects closer to the viewer exerts even more pressure on the brain to direct both the converging and focusing eye muscles to the same spot in space.
This also implies that what may appear as 'massive' 65-inch plasma and LED HDTVs, still represent a relatively medium size TV screen for a truly realistic 3D TV experience. A possible way out to partially solve this issue is to move closer to the TV screen for a more aggressive 3D experience; this means that a 1080p HDTV is a pre-requisite for 3D at home.
But as expressed earlier on, you cannot just move closer as much as you like since here arise the issue of fundamental disparity. In other words, the ability to get immersed into the movie action in 3D, becomes even more challenging in the case of 3D TV content because of the increased disparity between convergence and focusing.
This leads us to the conclusion that for a more realistic 3D TV viewing experience, you need to:
[a] Get the biggest TV screen size you can afford for your viewing distance, and to
[b] Move closer to the screen as is practically possible.
In the home, the TV screen size remains relatively small in comparison to the screen at the movie theater. To make up for the smaller TV screen size, one needs to move closer to the TV to maintain an adequate field of view for a more immersive 3D TV viewing experience.
Earlier on in our discussion, we stated that for an immersive 2D TV viewing in the home theater, THX recommendations translate to a viewing range that varies between 1.54 to 2.2 times the screen width for a 1080p HDTV. We have to translate this into the optimum 3D TV viewing distance while respecting the constraints resulting from both visual acuity and 3D TV comfort zone.
What turns this whole issue rather challenging is that in the case of a 3D image, there is no fixed distance of the image away from the viewer as in the case of 2D TV. Instead, you have two virtual extremes points within which the virtual 3D image resides, a nearest virtual point that is relatively close to the viewer, and a farthest virtual point. The real problem is:
How can we arrive at an optimal 3D TV viewing distance when the 3D image does not reside at a fixed distance away from the viewer?
In our opinion, a possible way forward to determine the best 3D TV viewing distance is to ensure that the average between these two virtual extreme points fall within the THX recommendations for an immersive viewing experience, while taking into account the visual acuity limitations for your TV screen resolution.
We will take the study already referred to above by In-Three, Inc. for comfortable 3D viewing in the home theater, as a basis for our analysis.
In-Three found that a person sitting at a close distance of 72-inches away from a 60-inch diagonal HDTV (corresponding to a screen width of 52.3-inches for a 16:9 HDTV), the virtual nearest point for that viewer appears at 51-inches away from the viewer; this is equivalent to 30% of the 3D TV viewing distance measured away from the screen surface, (where the 3D TV viewing distance is the actual measured physical distance between the viewer and the 3D TV screen.) On the other hand, the farthest 3D image point will appear at 120-inches away from the viewer, or about 165% of the 3D TV viewing distance, farther away from the viewer.
This leads to a virtual average 3D image distance that resides at approximately 85-inches away from the viewer, or 1.63 times the screen width for a 60-inch HDTV. This is within both the THX recommendations for an immersive viewing experience, as well as close to the limits associated with visual acuity for a 1080p image.
Yet, despite that the virtual average distance is 85-inches away from the viewer, the 60-inch diagonal TV screen is situated at 72-inches away from the viewer, or 1.4 times the screen width for a 16:9 HDTV. Thus...
For an immersive 3D TV viewing experience in the home:
The optimum 3D TV viewing distance should reside at approximately 1.4 times the TV screen width for a 1080p screen.
In the case of a 720p HDTV, the optimum 3D TV viewing distance corresponds to 2.1 times the TV screen width.
In both cases, these distances correspond to 0.78 times the distance as resulting from visual acuity for the respective screen resolution.
As you may have already noticed from this discussion, 3D TV viewing in the home presents a number of major challenges for the brain to successfully fuse the two slightly different images seen by the left and right eye into one virtual 3D image.
One important issue we did not mention yet has to do with where your seating position falls, within the field of view. The viewer is not only restricted to what constitute an optimum 3D TV viewing distance, but also to what constitute an optimum viewing angle for a more realistic 3D TV experience. Why?
For the viewer to enjoy a truly realistic 3D TV viewing experience in the home, one has to view the screen from an angle that matches the camera shooting angle used during filming.
Since current 3D content is shot from a fixed head-on perspective, the line from your seating position to the screen should be such as to represent a perpendicular to the screen surface, i.e. your 3D TV viewing position should be along the TV axis for a zero degrees viewing angle. This represents the sweet spot for the most realistic immersive 3D viewing experience.
Move away from this sweet spot and the resultant 3D image will soon start to appear somewhat abnormal as the brain tries to make sense of images seen by the left and right eyes, images that are shot from head-on but that are being viewed at an angle; the brain would expect to see a side view not a head-on view when viewing images from the side.
In other words... If you really want to make the best out of the latest 3D TV technology and get the best out of your new 3D HDTV, you should not only stay at a closer 3D TV viewing distance than is typical with 2D viewing, but also limit your TV viewing angle to as close as possible to zero degrees along the TV axis.
To enjoy the best 3D immersive experience in the home, you need to move closer to the TV and invest in the largest screen your budget and you room layout allow. A closer 3D TV viewing distance would help enhance the otherwise mild 3D experience in the home in comparison to the more aggressive 3D in the movie theater. This significantly less aggressive 3D experience in the home results from the reduced parallax necessary to remain within the comfort zone associated with the shooting of 3D content for home viewing.
Equally important, ensure that the seating layout is as close as possible to the zero degrees along the TV axis. The latter is not possible with multiple seating but limiting the number of seats should help ensure that each viewer will still enjoy a great 3D TV experience.
The optimum 3D TV viewing distance for a 1080p HDTV stands at 1.4 times the screen width, just slightly closer than the 1.54 resulting from the THX recommendations for an immersive 2D TV viewing experience. In the case of a 720p HDTV, the optimum 3D TV viewing distance is approximately at 2.1 times the screen width.
If you find these distances a bit too close for your liking, move a little farther away but try to remain within the 1.54x the screen width for 1080p HDTVs and 2.7x for a 720p HDTV.
We believe that the above recommendations for 3D TV viewing distance should help you arrive at an optimum viewing position for a most immersive and enjoyable 3D TV experience. However, do not be afraid to experiment with your 3D TV viewing distance to find the best spot for your liking.