Viewing angle:

• A viewer tends to position himself or herself relative to a scene so that the smallest detail of interest in the scene subtends an angle of about one minute of arc (1⁄60°), approximately the limit of angular discrimination for normal vision.

• For the 483 picture lines of conventional television, the corresponding viewing distance is about seven times picture height (PH); the horizontal viewing angle is about 11°.

• For the 1080 picture lines of HDTV, the optimum viewing distance is 3.3 screen heights, and the horizontal viewing angle is almost tripled to 28°.

Viewing distance:

• It is expressed in units of picture height should be about 3400 divided by the number of picture lines. A computer user tends to position himself or herself closer than this about 50 to 60 percent of this distance – but at this closer distance individual pixels are discernible.
• Consumer projection television is viewed closer than 7×PH, but at this distance scan lines become objectionable.

$$distance \approx \frac{3400}{lines} \times pH$$