Conversations on Colorblindness
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Part one of my conversation with Dennis G.

Dennis wrote -

I am an anomalous trichromate protan (red weakness) colorblind person. I enjoyed your WEB page on colorblindness. I agree with your assessment of the way the world uses color, it's too bad and so easy to change. I also have a weakness for red LEDs, but I can usually see most quit easily, just not as good as normal vision people. Because I am colorblind, I have a keen interests in how colorblindness affects my day to day life. From your description of not being able to see LEDs (red?), I can see LEDs if they are large enough, and bright enough, the smaller the letters or numbers the lesser my ability to distinguish.

I would assume you are a dichromate protan (no red cones). Red weakness makes up only 1/3 of colorblind people. The other 2/3's of colorblind people are weak/minus green. About 30% are dichromates (two cones) and 70% are anomalous trichromate fluorescentes (three cones with one weak one). I don't completely understand your following statement...

"Because it is a result of a rod and cone defect, colorblind people are also prone to night blindness or they may have extreme difficulty in seeing in low light, or their color perception may be greatly reduced in low light"

Marty Replied -

I did not mean to imply that colorblind people only have less color perception in low light. they have less color perception in both light and dark situations but some of us see less well as the level of illumination goes down, and also less well in different kinds of light. I for instance see well in daylight, but less well under fluorescent light and poorly under incandescent light. then again with a 40 watt bulb I have difficulty but with a 100 watt bulb it is better.

Dennis wrote -

I agree with color perception in low light levels, but colorblindness (as I understand it) does not pertain to the rods in the eye. In fact from what I have read, colorblind people see better at night than normal vision people.

I see less well at night than most people because the level of color input is so much lower that everything looks black. There is little to base differentiation between things on.

Dennis wrote -

I have measured my vision and have found that I see in the blue much better than normal people. I can spot a deep navy blue from black better than normal people. I wounder if you have found that you see better in the blue than normal vision people. I see at least 200-300 angstrom blue of a normal person i.e., in the near Ultra Violet. It's like my low red cone count has been offset by blue cones. The best way I can describe my blue sensitivity it blue (black light) disco light drive me nuts because they are so bright. I would enjoy hearing from you and I don't mean to be too corrective to your WEB page. May be I am wrong, but I would like to find out if I am.

Marty Replied -

I am not sure on what you base your measurements on. My blue/black differentiation is poor at best, and then only in bright daylight. Black on red, red on black, blue on red, red on blue, red on brown, etc. etc. are all poor.

On the other hand I have no problems with light on dark or dark on light where there is a high level of contrast between the components.

Marty Concluded -

Generally speaking, you can't do much generalizing about colorblindness. It differs from person to person.

I am shade blind (I have difficulty distinguishing between colors of the same intensity, especially "washed out" colors. Things like weather maps, in fact maps of all kinds are difficult to read because the colors blend together. I can see intense, pure colors, but have trouble with mixed colors (purple, maroon, etc.)

Red on black is almost invisible to me, I cannot distinguish between Navy Blue and Black, or dark Brown or dark red and black. Not enough color for me to detect.

I question your normal vision comment, because I am not sure there is such a thing. How can we tell what someone else sees? Visual acuity (is that the right word?) that is 20/20 versus something less. measures the sharpness of the vision. Measuring color is very objective. How do we know that what I know as red is what you know as red?

We can discuss this further if you would like.

Last updated March 5, 2001