1.4 Visual Principles Flashcards
Parameters that you must consider before selecting a
display
- Text size
- Farthest viewing distance
- Nearest viewing distance
- Good & acceptable viewing angles
Visual Acuity
Acuity is an eye’s ability to discern fine details .
Resolution acuity
the ability to detect that there are
two stimuli, rather than one, in the visual field
Recognition acuity
the ability to correctly identify a
visual target , as in differentiating between a “G’ ‘ and a
“C.”
rule for determining if on-screen text is legible
Text Height x 150 =maximum distance from the screen
Calculate Font height in pixels
Font inches/mm
Screen Height inches/mm
=
Font pixels Screen Height pixels
The 4, 6, 8 Rule
Height Ratio to distance from screen.
Screen Height * X
- Use 8 when the viewers will generally observe content.
- Use 6 when the viewers will inspect content with clues and
generally observe content. - Use 4 when the viewers will inspect content without clues.
How Close is Too Close?
lnfoComm says 1x the screen
width. This closely matches your eyes’ viewing angle (approximately 60
degrees for color discrimination).
Maximum
acceptable viewing angle
45° from the far edge of the screen
Calculate immage diagonal
A^{2}+B^{2}=C^{2}
Calculate immage diagonal
A^{2}+B^{2}=C^{2}
Calculate immage diagonal
\text{}
Projection Screen gain
the ability of a screen to redirect light energy in a
narrower viewing area, making projected images appear brighter to viewers sitting on axis to the screen. The higher the gain number of a
screen, the narrower the viewing angle over which it provides optimal
brightness.
Screen Finishes
Matte white, ambient light rejection,
Rear Projection Material (light passage)
Diffusion - Light in all directions
Lenticular - Focuses light with fade toward edges
Lenticular & Fresnet - Realigns light toward edges.
Incident Light Measurement units
- Lumen
- Footcandle
- Lux
Lumen
Lumen is a measure of the light quantity emitted from a
constant light source across one square meter .
Foot-Candle
Footcandle, abbreviated “fc,” is an English unit of
measurement expressing the intensity of light
illuminating an object. The illumination from one candle falling on a surface of 1 square foot at a distance of 1 foot.
One footcandle equals ? lux.
One footcandle equals 10.78 lux.
Lux
Lux is a combination of the words luminance and flux. One lux is equal to one lumen/square meter, or 0.093 footcandles.
Candela
candela measures luminance. It is used to measure the amount of light that is reflected off a surface. It differs from footcandles and lux because it measures reflected, not direct light.
Luminance (Lighting)
Luminance is the photometric quantity most closely
associated with one’s perception of brightness. It usually refers to the amount of light that reaches the eye of the observer measured in units of luminous intensity (candelas) per unit area (m 2).
Luminance (Camera)
Luminance is part of a bandwidth limited video signal. It combines sync and brightness information. It is also called “luma,” and “Y” is its abbreviation.
llluminance
Light falling on a surface, measured in Lux (Ix) or FootCandle (ft-c or fc) [1 lux = 0.09 fc] . Not visible to human eye other than in the form of reflected luminance.
System Black
System Black is the lowest level of luminance a system is capable of producing for its task operating conditions. The system includes projector, screen , the light the Glossary projector produces, and ambient light.
Contrast Ratio
Contrast ratio describes the dynamic video range of a
display device as a numeric relationship between the brightest color (typicaUy white) and the darkest color (typically black) that the system is capable of producing. Two methods are used to specify contrast ratio;
Projected Image System Contrast Ratio (PISCR) - ANSl/INFOCOMM 3M-2011
standard was developed to ensure high quality images.
- Passive viewing - 7:1
- Basic decision making -15: 1
- Analytical decision making - 50: 1
- Full-motion video (home theater) - 80: 1
five measurement (viewing) location
Front Left/Right
Rear Left/Right
Center
3M Conformance
CONFORMS - All five viewing angles pass contrast test
PARTIALLY CONFORMS - All but one of five conforms
All else fail
Hot Spot
A hot spot is the part of a displayed image that is
unevenly illuminated, usually appearing as a bright area
in the center .
Projector Brightness Formula
The formula for projector brightness is :
Brightness pJ = AL * SA * CR/ SG / DR
Where:
• BrightnessPi = Projector Brightness
• AL = Ambient Light Level
• Sa = Screen Area
• Cr = Contrast Ratio
• Sg = Screen Gain
• Dr .= De-rated precent (loss due to lamp life)
What should Task Light Levels be?
should be within +3 times and -3 times the brightness range of projected white.
