Horizontal Viewing Angles
The horizontal viewing angle is the angle subtended by a straight line from each side of the screen to the seating position. The main two standards in the commercial world are the SMPTE and THX specifications as summarized in the diagram below:
New cinemas built to THX specifications have a minimum viewing angle of 36 degrees from the last row of seats. The viewing angle 'sweet spot' seems to be around 45-50 degrees where SMPTE, THX and 20th Century Fox recommendations converge. This matches quite closely with CEDIA's 43 degree viewing angle recommendation for 2.4:1 'Cinemascope' content as per CEB-23. For reference 43 degrees is 3x picture height using a 2.35:1 screen.
Depending on where you like to sit in a commercial theater you might have a viewing angle of anywhere from 36 to 60 degrees. Personal preference is therefore an important factor and should be a prime consideration when laying out your home theater.
Image Resolution and Horizontal Viewing Angles
Visual acuity data give us useful information about when a person should be able to appreciate the full benefit of different resolutions.
- 480p - 4.1x width
- 720p - 2.7x width
- 1080p - 1.7x width (equivalent to 33 degrees viewing angle with a 2.35:1 screen)
- 4k - 0.8x width (over 60 degrees viewing angle with a 2.35:1 screen!)
Higher resolutions should allow us to sit closer to the screen for a more immersive experience. Likewise with lower resolutions we may want a smaller viewing angle so that deficiencies in the source's resolution are not overly exposed.
Vertical Viewing Angles
The CEDIA recommendation, which is based on SMPTE guidance, is or no viewer to have an angle of greater than 15 degrees to the top or bottom of the screen. Typically this puts viewers eye's at 1/3rd to 1/6th of screen height.
Dealing With Multiple Rows of Seats
In larger home theaters multiple rows of seats are common. This introduces some compromises and challenges:
- Horizontal viewing angles. Due to the smaller screen sizes and viewing distances in a home theater the viewing angle changes much faster than it would do in a cinema. A front row in a theater with three rows of seats might have a viewing angle of as much as 60 degrees with the back row only 26 degrees.
- Sightlines. With more than one row sightlines from second and subsequent rows to the screen can be blocked by viewer's heads. Typically this is dealt with using seating risers or horizontally staggered seating layouts. When using risers one must be careful not to exceed vertical viewing angle recommendations.
Need help laying out your home theater screen and seating locations for proper viewing angles? Contact us now!
About the author: Nyal Mellor is founder of Acoustic Frontiers, a company specializing in the design, build and calibration of high performance home theaters for enthusiasts worldwide.