The maximum angular distance from looking in front of a screen to looking from the side without a change of brightness or colors. A 180-degree angle means that there is no difference, which is fairly true for CRT and plasma screens. However, viewing angles differ between LCD and front and rear-projection screens.Both Horizontal and Vertical
Horizontal and vertical angles are often not the same. For example, looking down on a screen may have less of a viewing angle than from the side and more of a viewing angle than from the bottom.See For Yourself
Angle measurements are not uniform, because viewing angles are measured as the contrast between black and white, and what is considered an acceptable contrast ratio differs among vendors. The best way to measure a viewing angle is to see for yourself: look straight on and then from the side or, if required, from the top or bottom.