Forth 3 Flashcards
What’s contrast ?
caused by a difference between the brightness of an object and its immediate background.
How contrast cause glare ?
When there is highly bright object against a dark background or different colored object cause discomfort and interference with our visual information and this interference called glare
Excessive contrast cause glare
Which object is easily to pickup ?
With high contrast than low
How much ratio of ambient light for teeth ?
3:1
Teeth should not be significantly brighter than the ambient environment
How does dental photography cause glare ?
By using black background that increase impact causing glare
What’s happen when we use dental photography to match a shade in high glare ?
This is counter-productive when matching Hue and Chroma due to increase in glare it will mask shade mismatch so don’t choose black background for shade match
How does human eyes preceive color ?
Humans have three visual pigments, each in different cone shaped receptor cells. ( they found in this cells)
One pigment senses primarily blue light
one primarily green
and one primarily red.
How does the color signal get transmitted to the brain ?
It is thought that impulses from the three types of receptor cones are somehow combined into
a coded signal prior to transmission from the eye to higher visual centers in the brain.
The combination takes place in the ganglion cells in the retina.
Changes in the color stimulus change the patterns of the coded signals.
Does eye can disguinsh the component of the colour that we see ?
The eye cannot distinguish the component wavelengths in a color sample.
Two lights of different colors when mixed produce a third color, and no human eye can detect its composite nature (Figures 6 a, b).
Ultimately the perceived hue is the dominant or the average wavelength.
The ability to perceive color dif-ferences varies from person to person.
How does lip stick red one affect shade selection ?
If you have strong red lipstick next to the tooth you are evalu-ating, the red receptors in your roaming eyes become fatigued while the blue and green receptors remain fresh and can be fully stimulated.
This can yield a perception of the tooth that is more blue-green than it really is.
Which reflective background color for shade selection ? ( see the paragraph of afterimage )
18% reflective gray card is also an excellent background for photographic evaluation of hue and chroma
Our ability to perform the task of shade selection de- pends on how well our eyes perceive the details of teeth. Factors determining the visibility or “seeability” of these details include ?
- Ambient light quality
- Luminance ( light quantity)
- Size
- Contrast and glare
Dental unit lights are commonly used for color rendering what’s the type of light in this units ?
.Most are incandescent lights that emit light high in the red-yellow spectrum and low at the blue end.
If we illuminate opaque samples of red, yellow, and blue under the incandescent light source what we will see ?
we will see that red and yellow are quite strong or highly saturated
while blue is weaker and more difficult to see.
Under an ordinary cool white fluorescent source, which is high in the green-yellow spectrum with some strong but narrow blue spectrum spikes, what’s happen to the the reds and violets?
are less apparent
