Light and color

examples of perception problems

While we can all “see”• Our ability to perceive color is a

very individual characteristic

• Apparently our eyes work the same way,but just as some people have differing athletic abilities,we also have differing perceptual abilities

This presentation illustrates some of these differences.

In the first set of slides

• The intersections of the white lines are completely clear,

• But many people perceive “spots” in the intersections away from where the are focused.

• This effect may be stronger or weaker, depending on the background color

In the next set of slides

• Some people perceive the pattern to be rotating

• Yet the circles are not moving . . .

• Again, the intensity of the perception may depend on the background color

The next set of slides illustrate the manner in which the rods assist our

visionInstructions :• Stare at the black spot in the center of the slide• Be aware that you can read the other letters

even while looking only at the center letter.

• Then shift you focus to a letter in the first ring• Be aware that the center spot is fuzzy, but the

other, outer, larger letters are still in focus

• Now shift your focus to a letter in the 2nd ring• Be aware that the smaller letters are now hard

to identify while the outer letters are still clear• Repeat these steps until you reach the outer

ring.

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Again, color of background seems to change the

effects for some people

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The accumulative effectof these individual differences

• Has a pronounced effect on our ability to read material.

• Be aware of differences in your reading ability based on the background colors, even though you are already familiar with the text.

Procedure:

1.      Practice releasing the steel from the top of the launching ramp. Develop a method that produces a consistent release. Se sure to catch the steely and not allow it to strike the backstop while practicing.2.      Once you have developed a consistent release method align the backstop with the right most vertical line.3.      Gently tighten the backstop to prevent if from moving.4.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.5.      Align the backstop with the next vertical line to the left.6.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.

Continue this procedure until 3 marks have been made at each of the vertical line positions.

Procedure:

1.      Practice releasing the steel from the top of the launching ramp. Develop a method that produces a consistent release. Se sure to catch the steely and not allow it to strike the backstop while practicing.2.      Once you have developed a consistent release method align the backstop with the right most vertical line.3.      Gently tighten the backstop to prevent if from moving.4.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.5.      Align the backstop with the next vertical line to the left.6.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.

Continue this procedure until 3 marks have been made at each of the vertical line positions.

Procedure:

1.      Practice releasing the steel from the top of the launching ramp. Develop a method that produces a consistent release. Se sure to catch the steely and not allow it to strike the backstop while practicing.2.      Once you have developed a consistent release method align the backstop with the right most vertical line.3.      Gently tighten the backstop to prevent if from moving.4.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.5.      Align the backstop with the next vertical line to the left.6.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.

Continue this procedure until 3 marks have been made at each of the vertical line positions.

Procedure:

1.      Practice releasing the steel from the top of the launching ramp. Develop a method that produces a consistent release. Se sure to catch the steely and not allow it to strike the backstop while practicing.2.      Once you have developed a consistent release method align the backstop with the right most vertical line.3.      Gently tighten the backstop to prevent if from moving.4.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.5.      Align the backstop with the next vertical line to the left.6.      Release the steely 3 times from the top of the launching ramp. Each time will produce a mark on the backside of the marking paper.

Continue this procedure until 3 marks have been made at each of the vertical line positions.

These examples illustrate differences in reading ability

are caused by other unrecognized factors that are not normally associated with reading ability.

Providing appropriate lighting (color) is a critical aspect of establishing a good reading environment for many people.

Other examples of reading difficulties associated with color

perception

This is easy to read, so you can decide to ignore it very rapidly

Very low contrast text is read by the part of the brain which locates objects, the “where” system.

As long as the words are easy to recognize, you can read rather rapidly, but recondite or infrequently encountered words seem unfamiliar and have to be read letter-by-letter.

This is also hard to read. It jumps around and seems unstable because the “where” system has trouble seeing it. Advertisers use this trick to make you pay attention because you have to slow down and read each individual word.

This is also hard to read. It jumps around and seems unstable because the “where” system has trouble seeing it. Advertisers use this trick to make you pay attention because you have to slow down and read each individual word.

Changing the color of the letters helps a lot

This is also hard to read. It jumps around and seems unstable because the “where” system has trouble seeing it. Advertisers use this trick to make you pay attention because you have to slow down and read each individual word.

Changing the background color also helps a lot

This is hard to read even though each individual letter is easy to see, so you have to pay a lot of attention in order to read it.

Final example• Retinal fatigue . . .

Causes an apparent “saturation” in the signal being sent to the brain along the optic nerve

• When a different “background noise level” is presented, the persistence of the saturation signal creates an “illusion”, an image that exists in the brain but not in reality . . . .