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What is a perfect score on the 100 hue test?


The 100 hue test is a method of evaluating color vision and color discrimination ability. In this test, a person is asked to arrange a set of 100 colored caps in order based on hue. The caps have subtle gradations in color that can be difficult to distinguish for those with color vision deficiencies. A perfect score on the 100 hue test is achieved by correctly sequencing all 100 color caps. This indicates normal color vision and excellent color discrimination ability.

What is the 100 hue test?

The 100 hue test was developed by Dr. Shinobu Ishihara in the 1960s as an improved version of his original color vision test using pseudoisochromatic plates. The test consists of four boxes containing a total of 85 movable color caps and 16 fixed anchor caps. The caps span the visible spectrum of color in gradual increments.

The person taking the test is instructed to arrange the movable caps in order of hue between the fixed anchor caps starting with purple and ending with red. The spacing between caps should be equal based on perceptible differences in color. The arrangement is scored by calculating the number of caps that are out of sequence from the correct order.

The 100 hue test provides a more comprehensive assessment of color vision compared to other screening plates. It is sensitive to subtle deficiencies in the blue-yellow and red-green color axes. The test can identify mild anomalies, acquired defects, or shifts in color perception that may elude detection on simpler color vision tests.

What is a perfect score?

A perfect score on the 100 hue test is 0, meaning that all of the 85 movable color caps were placed in correct sequential order. This demonstrates normal color vision with excellent ability to discriminate between subtle gradations in hue across the full visible spectrum.

Total Error Score Color Vision Assessment
0 Normal
1-10 Minimal deficiency
11-20 Mild deficiency
21-30 Moderate deficiency
31-85 Severe deficiency

As shown in the table above, a perfect score of 0 indicates normal color vision. Scores between 1-10 are considered minimal deficiencies, 11-20 mild deficiencies, 21-30 moderate deficiencies, and 31-85 severe deficiencies.

The maximum potential error score is 85 if all of the movable caps were arranged randomly or completely out of order. This would indicate extreme color blindness. However, such profound defects are rare. Most color vision problems fall in the mild to moderate range on the 100 hue test scale.

Who can achieve a perfect score?

Only people with normal color vision and intact color discrimination ability are capable of achieving a perfect score of 0 on the 100 hue test. This rules out those with any level of color vision deficiency:

– Red-green color blindness (protan and deutan defects)
– Blue-yellow color blindness (tritan defects)
– Acquired color vision defects from disease or injury
– Inherited anomalies like color blindness in women

Congenital red-green color blindness is the most common type, affecting about 1 in 12 men and 1 in 200 women of Northern European descent. This makes it difficult to perfectly arrange the warm end of the caps sequence from green to red. Blue-yellow defects are rarer but would interfere with sequencing the blue-violet end accurately.

Other factors like aging can reduce color sensitivity and make it harder to detect subtle hue differences. Younger people are more likely to achieve perfect scores. Research shows that color discrimination ability peaks around 20 years old and gradually declines with age.

Tips for achieving a perfect score

Here are some tips to optimize your chances of achieving a perfect 0 score on the 100 hue test:

– Confirm you have normal color vision. Simple screening tests like Ishihara plates can detect major deficiencies.

– Get plenty of sleep before testing. Fatigue diminishes color discrimination.

– Avoid medications and supplements that affect color perception like antihistamines.

– Take the test in a well-lit room with natural daylight illumination.

– Calibrate your color perception by looking at the anchor caps first.

– Focus on hue rather than brightness or saturation.

– Compare each cap carefully to adjacent caps to detect subtle gradations.

– Work slowly and methodically without second-guessing your arrangements.

– Double check your sequence once completed. Make minor adjustments if needed.

Does everyone with normal color vision score perfectly?

While a perfect score generally indicates normal color vision, not everyone with normal color vision will score 0 on the 100 hue test. Small errors can occur due to:

– Inattention – Momentary lapses in focus may lead to one or two caps placed out of order.

– Fatigue – Color discrimination deteriorates when tired, even in those with normal vision.

– Learning effect – Some improvement is seen on repeat testing from learning and sequence recall.

– Age – Color discrimination peaks in the 20s and declines with aging at variable rates.

– Test conditions – Poor lighting, glare, or color contrasts in the testing environment.

– Anchor cap spacing – Altering the spacing between fixed anchor caps can increase difficulty.

So a perfect score clearly demonstrates excellent color discrimination, but one or two minor sequencing errors do not necessarily indicate color vision deficiency in people with normal color vision. Scores between 1-3 are still considered within the normal range for this test.

Should the test be repeated for confirmation?

It can be useful to repeat the 100 hue test under controlled conditions when evaluating a person’s overall color discrimination ability. Reasons for retesting include:

– Confirming a perfect score was not due to chance. Scores of 0 are rare, even in those with normal color vision.

– Verifying minor errors were not due to temporary factors like fatigue or lapses in concentration.

– Ensuring test conditions were optimized for peak performance.

– Assessing for improvement from a learning effect after the initial sequence arrangement.

– Monitoring for deteriorating scores over time that might indicate an acquired color vision defect.

– Comparing results on different versions of the test when available. Varied anchor cap spacing or color increments may impact difficulty.

Repeating the test allows for consistency in the results, providing a clearer measure of the examinee’s inherent color discrimination abilities under favorable test conditions. Consistently perfect scores confirm excellent color vision.


A perfect score of 0 errors on the 100 hue test demonstrates normal color vision and excellent ability to discriminate subtle gradations in hue. It is a challenging level of performance that requires intact color perception across all color axes. Minor deficiencies in any part of the color spectrum will interfere with perfectly sequencing the caps. Though a rare achievement, perfect scores are attainable by those with normal color vision who are meticulous, motivated, and tested under ideal conditions. Confirming the ability to consistently score 0 verifies superior color discrimination abilities.