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
52 IVC classrooms
Dozens of smaller conference rooms
Predominately using TVs, but some spaces have projectors - moving towards lampless projectors

3. 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

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

7. Viewer distance and ratio are known -
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 -
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 -
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. 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

12. 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

13. 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

14. 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

15. 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

16. 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)
Theatrical movie (37:20, 98:41)
Ratios expressed as single numbers
( 4: ), ( 5: ), ( 16: ), ( 16: ), (21: ) (Monitors, TVs, Projectors)
37: / 98: (Theatrical movie)

17. 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

18. Viewing distance / resolution chart
All ratio of 8 sizes/distances follow the bottom of the “all appear to be equivalent” range
All ratio of 6 sizes/distances goes right down the middle of the “720p starts to become noticeable” range
All ratio of 4 sizes/distances goes right down the middle of the “1080p starts to become noticeable” range

19. 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 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)

20. Basic Decision Making
Ability to see and read the content in order to make basic decisions
Contracts or basic images
Farthest viewing distance = Image height * BDM * % Element
Image Height = Farthest viewing distance / (BDM * % Element)
BDM = 215
Content can be scaled up or down
90” LCD viewed at 25’ needs 1.3” high text

21. Analytical Decision Making
Ability to see every detail of a document or image, possibly down to the individual pixels
X-rays or photographs used in court proceedings
Farthest viewing distance = (Image height X ADM) / # vertical pixels
Image height = (Farthest viewing distance * # vertical pixels) / ADM
ADM = 3438
Content should not be scaled
90” LCD viewed at 25’ needs ~ 500 vertical pixels (960x540 qHD)

22. Impact of display height

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

24. Basic Decision Making

25. Analytical Decision Making