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How Far Should I Sit From My HDTV?
Buying a HDTV can be challenging exercise for newcomers. In the past, the small size of CRT TVs, together with technological limitations and poor analogue signal made our choice easier; by and large most CRT TVs look the same at average viewing distances. Nowadays, HDTVs come in many sizes ranging from 28 inch to 65 inches, and in very different technologies too. This has a significant impact on the optimum viewing distance related to the size of the TV, and is probably the first thing you should think of before taking the plunge.
There are many factors that influence optimum viewing distance. Please note that the below factors are primarily for fixed pixel technologies (e.g. Plasma, LCDs).
1) Maximum Detail Perception
The latest HD revolution is really about providing detailed images on larger screens, without the annoying artifacts inherent in standard analogue broadcast. In modern flat panel displays, the images are formed on a grid of tightly packed pixels. Imagine watching this grid at a very small distance; you will immediately appreciate the "pixelation" problems that affect some viewers. But if you walk slowly back, you can see the pixel grid slowly disappearing to form a smooth image. At that point, you are able to see all the detail that was intended when the picture was transferred from a digital master.
Now that optimum viewing distance is of course affected by individual visual acuity and surroundings . But in general, the pixelation threshold is about 1.5 times the diagonal viewing distance of your TV at 1080 material. If you move further back the image will start to lose detail by these pixels `fusing’ into one another ie. not being able to make out the detail of an object at a large distance.
2) Viewing Angle
SMPTE and THX recommends that optimum viewing distance should also give a viewing angle of 30 degrees for an immersive cinematic experience. This is harder to control in home situations, but is possible on some large TV sets or home projectors. However, I would definitely act in favour of maximizing detail and eliminating the pixelation effect first.
3) HD Resolution Material
Most of the HD source are encoded in either 720 or 1080 resolution. This is important because when you think of it, 1080 material provides greater detail than a 720 material on a 1080 screen. So, if you upgrade the resolution, you can sit closer to the TV and enjoy the increased detail and viewing angle. I’ll make this clear in our example below.
4) TV Size
TV size and viewing distance are related. Changing both aspects always change the TV size in your eyes.
Ok. Here is the example.
Some rules.
1) Viewing distance – Too near, pixelation. Too far, loss of detail.
2) TV size – Too large, pixelation, Too small, loss of detail.
3) Material resolution – Too low, pixelation, Too high, motion sickness. (Haha we'll talk about it some other time.)
4) All changes in the above factors, must take into account that you always eliminate pixelation first, and then maximizing detail at the `optimum’ distance.
So in my guide, assuming 1080p capable TV:
40 inch diagonal TV – 720 material – 8 feet (optimum pixelation/detail threshold)
1) Buy a larger TV (50 inch) without changing the other factors means you run risk of poorer picture quality due to increased pixelation. Using the above rules, you can sit further (10 feet) or increase the resolution to 1080 to counter this.
2) Increasing the resolution of the material to 1080 does not cause any pixelation, but you may lose the extra detail it affords. In effect, the 720 and 1080 material are indistinguishable at this distance to most viewers, all things kept the same. The new optimum distance should now be about 5 feet. Conversely, watching poor resolution material means that you have to sit further away to avoid pixelation.
3) Changing viewing distance has siimilar effect as changing the TV size. If I sit too near to the TV, I would need smaller TV to counter its effect or watch higher resolution material.
So that’s it for now. I have included a table relating viewing distance, size of TV and material resolution below for 1080p widescreen TV sets. The highlighted ones means they also enjoy a 30 degree viewing angle.
| 576 resolution | 720 | 1080 | |
| 32" inches | 8' feet | 6' | 4' |
| 37" | 10' | 7' | 5' |
| 40" | 10.5' | 8' | 5' |
| 42" | 11' | 8' | 5.5' |
| 46" | 12' | 9' | 6' |
| 50" | 13' | 10' | 6.5' |
| 52" | 13.5' | 10' | 7' |
| 65" | 17' | 13' | 8.5' |
* The above is the minimum sitting distance from a 1080p TV
I was wondering if you had a similar table for maximum viewing distances. I.e the distances at which the definition of an HD set would not be appreciated by the viewer.
For instance in my case I will be 17 feet from the set so judging by the table above this would be optimum for a 65inch set at 576 resolution. Does this mean that there is little point in purchasing a higher resolution and rather than paying extra for resolution I should invest in the biggest low res set I can afford?
Yes you are correct. At 17 feet, you should opt for size over resolution if you intend to watch SD resolution.
This table was built on the assumption of a 1080p set and to maximise detail, but the lowest resolution, whether from the TV or the material will be the limiting factor. So it you watch a 576i from a 1080p, you should look at 576 to calculate your sitting distance. Similarly, if you watch 1080p over a 720p TV, the limiting factor would now be the 720 TV resolution. I hope this is not too confusing.