A look into the science and math of how to select a screen size for your classroom or other space.

1. Size Matters
By Mike “Kirby”

2. • Can everyone hear?
• Can everyone see?
• Can the message be portrayed in a way
everyone will understand it?
Purpose of the Room

3. • What is the Task
• 4, 6, 8 Rule
• Text Size Requirements
• Viewing Distances
• Screen Height
• Screen Size and Location
• Aspect Ratio and Resolution
Determining Display Size

4. • View: General Viewing
• i.e. Watching TV, Pictures, Video Conf.
• Read: Detailed Viewing with Clues
• i.e. PowerPoint, Websites
• Inspect: Detailed Viewing without Clues
• i.e. Excel, CAD Files, Road Maps
What is the task?

5. Distance to Least Favored Viewer (LFV):
4, 6, 8 Rule
• Viewing: LFV/8
• Reading: LFV/6
• Inspecting: LFV/4
• 24/8 = 3 feet
• 24/6 = 4 feet
• 24/4 = 6 feet
*LFV = furthest from screen

6. • Image Legibility Test 20 Point Arial
• Image Legibility Test 20 Point Times New Roman
• Image Legibility Test 18 Point Arial
• Image Legibility Test 18 Point Times New Roman
• Image Legibility Test 16 Point Arial
• Image Legibility Test 16 Point Times New Roman
• Image Legibility Test 14 Point Arial
• Image Legibility Test 14 Point Times New Roman
• Image Legibility Test 12 Point Arial
• Image Legibility Test 12 Point Times New Roman
• Image Legibility Test 10 Point Arial
• Image Legibility Test 10 Point Times New Roman
• Image Legibility Test 8 Point Arial
• Image Legibility Test 8 Point Times New Roman
• Image Legibility Test 6 Point Arial
• Image Legibility Test 6 Point Times New Roman
• Image Legibility Test 4 Point Arial
• Image Legibility Test 4 Point Times New Roman
What Font Can You Read?

7. 1-Minute of Arc is the smallest angle that the human eye
can see under ideal conditions.
1-Minute of Arc is 1/60 of a degree.
Human Eye

8. 20/20 Vision is 5 Minutes of Arc
20/40 Vision is 10 Minutes of Arc
Human Eye
Normal visual acuity (20/20) is
the ability to resolve a spatial
pattern separated by one minute
of arc.

9. For 20/20: α is 5 minutes of arc or 1/12 of a degree
For 20/40: α is 10 minutes of arc or 1/6 of a degree
What does 20/20 mean?

10. “The height of the smallest character shall
not be less than 10 minutes of arc on the
retina of any viewer.” (20/40 vision)
Dr. Joy Ebben, Ph.D
Smallest Character Size

11. Distance to LFV (feet) Min. Character Height (inches)
16
18
20
22
24
26
28
30
32
34
36
38
40
42
0.57
0.64
0.71
0.78
0.85
0.92
0.99
1.06
1.13
1.2
1.28
1.35
1.42
1.49
Distance Distance x 0.035625
Character Size

12. • Computers use Points for text size
• Point comes from printing
• 72 Points in one inch
• Display size changes the size of the character –
points are meaningless to projected displays
Point vs. Pixel

13. • Screen 30 ft away
• Factor of 6 for Reading
• 5 ft (60”) high screen
• Minimum Font Height we are about 1”
• 60” divided by 768 (vertical pixels) = 12.8
pixels per inch
• Use font size 13 or higher
Font Size

14. • Average head height (seated) is about 4’0”
• Average eye height (seated) is about 3’6”
• Image looks better if no less than 6” from the ceiling
• Ideally the lowest the screen can go is 3’6” from the
finished floor
Sight Lines
4’0”
3’6
”

15. Viewing Angles
Normal line of sight is 15o up or down

16. • The best viewing is on axis.
• Maximum viewing distance is based on
the detail of the image.
• The off-axis view angle will be dependent
on the surface the image is viewed on.
Define the Viewing Area

17. Viewing Area
• Ideal viewing cone is 45o from center line.
• Acceptable viewing cone is 45o from the edges

18. • Varied answers
• 4 diagonals
• 1 diagonal
• Image within field of view (30o)
• Some people sit in the front row of the
movie theater!
How Close – Nearest Viewer

19. First row should be no closer than the
screen than the width of the image.
(about a 52o viewing cone)
How Close – Nearest Viewer

20. • Ceiling at 9’
• Image 6” below ceiling
• Top of image is 8’6” AFF
• Bottom of image is 3’6” AFF
• 8’6”-3’6” = 5’ High
• 5’ x factor of 6 = LFV at 30 feet
Classroom Example

21. • Horizontal dimension of an image
expressed in relation to the vertical
dimension.
Aspect Ratio

22. Standard Definition 4:3
Aspect Ratio - Standard
4 Units
3 Units4
3
= 1.33

23. Aspect Ratio - HDTV
High Definition 16:9
16 Units
9 Units16
9
= 1.78

24. Aspect Ratio – HD Computer
High Definition 16:10
16 Units
10 Units16
10
= 1.60

25. Common Resolutions
16:9
3840 x 2160 4K Ultra HD
1920 X 1080 – 1080p (Full) HD
1366 x 768
1280 x 720 – 720p HD
16:10
2560 x 1600 WQXGA
1920 x 1200 WUXGA
1440 x 900 WXGA+
1280 x 800 WXGA
4:3
2048 x 1536 QXGA
1024 x 768 XGA
800 x 600 SVGA
640 x 480 VGA

27. • 5’ or 60” Height
• 4:3 (60” x 1.33) 79.8” or 6.65’ Wide
• 16:9 (60” x 1.78) 106.8” or 8.9’ Wide
• 16:10 (60” x 1.60) 96” or 8’ Wide
Classroom Example

28. • 16:9 Aspect Ratio
• Width = Diagonal x 0.8693
• Height = Diagonal x 0.4886
Determining LCD Size

29. 60” LCD

30. • 29.375” High for 60” Display
• 29.375 x factor of 6 = 176.25” or
60” Classroom Display

31. Diagonal Width Height LFV In LFV Ft
22 19.12 10.75 64.50 5.37
32 27.82 15.64 93.81 7.82
40 34.77 19.54 117.26 9.77
47 40.86 22.96 137.79 11.48
55 47.81 26.87 161.24 13.44
60 52.16 29.32 175.90 14.66
70 60.85 34.20 205.21 17.10
80 69.54 39.09 234.53 19.54
84 73.02 41.04 246.25 20.52
90 78.24 43.97 263.84 21.99
95 82.58 46.42 278.50 23.21
103 89.54 50.33 301.95 25.16

32. Will the LCD be Cheaper?

33. • 4, 6, 8 Rule for LFV
• Character Height should be the driving
factor in determining the height of the
screen.
• Aspect Ratio does not effect Character
Height
• Ceiling height is often the limiting factor
for the screen size.
Conclusion

34. To download this presentation go to:
http://tinyurl.com/nvuutnm
Get this Presentation
Mike “Kirby”
mkirby@gencomminc.com
(801) 971-8936
State Contract# MA513