1. Classroom Display Sizes
Just how big do they need to be?
Timothy A. Dunbar, CTS Director of Computers and Instructional Technology Northcentral Technical College

2. Northcentral Technical College
Main campus in Wausau WI, with 6 regional campuses and several Centers of Excellence spread out over 10 counties
118 Smart classrooms
55 IVC classrooms
Dozens of smaller conference rooms
Predominately using TVs, but some spaces have projectors - moving towards lampless projectors

3. The math behind the decision…
We will go over two different ways to determine the proper display size
Older non-standard “standard”
Newer ANSI standard

4. 4-6-8 rule
Examples of the images requiring each ratio
8 - General: movies, talking head
6 - Detailed: PowerPoint, reading with clues
4 - Inspection: CAD drawings, reading without clues
A rule that has been around for a long time. It has been replaced as of May, 2016

5. How to calculate the required display size, the maximum viewer distance, or the expected ratio - Pythagorean theorem (a2+b2=c2)

7. Viewer distance and ratio are known -
Furthest viewer distance / Ratio = Display height
Take furthest viewer distance in feet, multiply by 12 to get inches, then divide by 4 or 6 or 8. Divide by 9, then multiply by (for 16:9), round up to the nearest diagonal measure for a display.
25’ distance - ratio of 8
25 x 12 / 8 / 9 x = 76.5” or 80” display

8. Display size and ratio are known -
Display height x Ratio = Furthest viewer distance
Divide the diagonal measure of the display in inches by (for 16:9), then multiply by 9. Multiply by 4 or 6 or 8 and divide by 12 to get distance to the furthest viewer in feet.
80” display - ratio of 8
80 / x 9 x 8 / 12 = 26’ furthest viewer distance

9. Viewer distance and display size are known -
Furthest viewer distance / Display height = Ratio
Take furthest viewer distance in feet, multiply by 12 to get inches. Divide that by the height of the display (Divide the diagonal measure of the display in inches by (for 16:9), then multiply by 9) to get the ratio of the room and its display.
25’ distance - 80” display
25 x 12 / (80 / x 9 ) = 7.65 ratio

10. Width & Height vs ratios (16:9)
Display size
Viewing Distance
Diagonal
Width
Height
4 ratio
6 ratio
8 ratio
Inches
inches
Feet 22
19.17
10.78
3.59
5.39
7.19 26
22.66
12.75
4.25
6.37
8.50 32
27.89
15.69
5.23
7.84
10.46 37
32.24
18.14
6.05
9.07
12.09 42
36.60
20.59
6.86
10.29
13.73 47
40.96
23.04
7.68
11.52
15.36 50
43.57
24.51
8.17
12.25
16.34 55
47.93
26.96
8.99
13.48
17.97 60
52.29
29.41
9.80
14.71
19.61 65
56.64
31.86
10.62
15.93
21.24 70
61.00
34.31
11.44
17.16
22.88 80
69.72
39.22
13.07
26.14 90
78.43
44.12
22.06
100
87.15
49.02
32.68
110
95.86
53.92
35.95
120
104.58
58.82

11. Updates to 4-6-8 rule due to digital content & higher resolutions
ANSI/INFOCOMM V202.01:2016
May 2016
Looks at the detail of the content as well as the physical ability for the eye to pick out details
Uses image height, pixel size, degrees of arc, and other factors in the formulas
It has two levels instead of three
Basic Decision Making (BDM)
Analytical Decision making (ADM)

12. Basic Decision Making
Ability to see and read the content in order to make basic decisions
Contracts or basic images
Uses the constant of 200 for BDM
Furthest viewing distance = Image height x BDM x % Element
Image Height = Furthest viewing distance / (BDM x % Element)
Content can be scaled up or down
90” LCD viewed at 25’ needs 1.5” high text (44 pitch font - no scaling)

13. Analytical Decision Making
Ability to see every detail of a document or image, possibly down to the individual pixels
X-rays, photographs, evidence used in court proceedings
Uses the constant of 3438 for ADM
Furthest viewing distance = (Image height / # vertical pixels) x ADM
Image height = (Furthest viewing distance x # vertical pixels) / ADM
Content should not be scaled
90” LCD with 1920 x 1080 should be viewed no further than 11’8”

14. Minimum distance
Closest viewer should not be less than the image’s width from the display
Provides good side to side view without having to turn your head

15. View angle
The view angle to the top of the image should be no more than 30 degrees up from level
Helps prevent sore necks and viewer fatigue

16. Distance from floor Allows people in the 2nd + rows to see better
Image height from floor
24” to 36” for tiered seating or a very shallow room
40” to 48” for flat floor seating
Allows people in the 2nd + rows to see better

17. Too low and too small for content shown (8
Too low and too small for content shown (8.1 ratio) 8’ High screen, 2’ from floor in 65’ deep room

18. Too high, but a good size for content shown (6
Too high, but a good size for content shown (6.7 ratio) 6’ High screen, 6’ from floor in a 40’ deep room, 23/35 degree

19. Aspect ratios Ratios PC Monitors (4:3, 5:4, 16:9, 16:10, 21:9)
TVs (4:3, 16:9)
Projectors (4:3, 5:4, 16:9, 16:10)
Ratios expressed as single numbers
( 4: ), ( 5: ), ( 16: ), ( 16: ), (21: ) (Monitors, TVs, Projectors)

20. Screen resolution chart
800
960
1024
1136
1152
1280
1366
1400
1440
1600
1680
1792
1856
1920
2048
2560
3440
600
4:3
16:10
1.33
640
16:9
5:4
1.25
720
1.78
768
1.6
21:9
2.39
864
900
1050
1080
1200
1344
1392
1536

21. Applying this to a 5,000 sq ft auditorium remodel

22. Impact of display height

23. Thank you
Timothy A. Dunbar, CTS Director of Computers and Instructional Technology Northcentral Technical College

24. Analytical Decision Making

25. Basic Decision Making