Part two of my conversation with Dennis G.

Dennis wrote -

By all means let us continue this discussion, if that would be ok. I have learned the most about colorblindness from other colorblind people I meet.

Marty Replied -

And I as well.

First let me back step back a little and describe my self and my >profession and interests. I work as an aerospece engineer and have a an Ph.D.. degree in astronomy . Since I was a kid (I am 37)

Marty Replied -

I am a 55 year old computer systems analyst, designer and project manager. Although I donot deal with color per se, I must use products which have preset color schemes, and in fact I have to use hardware with indicators which were not made for colorblind people.

I have a great deal of difficulty when viewing things where color makes a difference. Let me explain. Maps (and TV weather maps) all use color gradations to distinguish between topographical features, or water depths, or even political boundries. These are difficult to see. A movie or show where there are color differences but where it doesn't necessarily make much difference what they are so long as you can tell that there are differences are fine, but sometimes they put title text in red on black, or yellow on green, or use one of the combinations which I can not see, or can only see with difficulty and then I am reminded of my disability.

In my case I can not see the numbers or letters on the colorblindness charts, but can distingusih between different primary colors

I find it interesting that you as a color blind person should chose a profession where color differentiation would seem to be so important (i.e. spectral analysis., etc.)

Dennis wrote -

So colorblindness severity (color perception) varies from person to person, its just that some of us have a severity that is labeled as colorblind.

Marty Replied -

Interesting though that color blindness may be due to a lack of sensitivity to certain colors of the spectrum rather than a complete lack of rods.

Dennis wrote -

I once had a friend who was colorblind and the green stop light was much dimmer to them than the yellow and red and to me the red stop light is the dimmer of the three, this person was a duetan.

Marty Replied -

I on the otherhand can see each of the lights equally well, and can see each one differently, but have difficulty telling the green lights from the street lights. (green light vs. blue/while light?)

Dennis wrote -

So there are some generalization one can make about colorblindness. I can totally relate to your descriptions about what you see because your description fits for me except I may have a little more red sensitivity. I can see red on black, its just annoying for me to read.

Marty Replied -

I can see red very well, but not red on black...

Dennis wrote -

I can see different colors on maps its just a little hard for me to tell what colors they are. In other words I can usually tell which color relates to which temperature on a temp. map, I just can't always tell if yellow is green, tan is brown, and so on, but I can usually match the color to the color code.

Marty Replied -

Sounds like me.

Dennis wrote -

I have "normal" color vision for colors that go from green to blue, but when it comes to telling purple from blue I have trouble when the lighting is poor or the color is only slightly purple. I can see pink and tell baby pink from a hot wild hot pink, its just that when they get weak I have trouble. I can tell a forest green for a pea green. I (my mother) was told by a child doctor that I am pastel colorblind which means I am one of those with one cone that is fewer in number or is modified (weaker three color vision). I found out in adulthood that the cones happened to be my red cones.

Marty Replied -

I can also see pink but cannot tell one shade from another. I can see light green from dark green, but as you I am pastel blind.

Dennis wrote -

As for night vision there may be another kind of vision deficiency that I am unaware of. When you refer to poor night vision, are you referring to poor color perception or poor object recognition.

Marty Replied -

My low light vision is good - I cna navigate my room at night with no lights on. But you could say I have poor object recognition. It is especially bad when I am in the dark but there is a bright light somewhere (such as a distant on-coming car headlight)

Dennis wrote -

I happen to see perfectly well at night and for the most part there is little to no difference in my object recognition at night when compared to others. As an amateur astronomer (when I was a kid) I have compared my vision to "normal" vision people when looking at nebulae that emit most there light in the very deep red region of the spectrum. I am suppose to be weak in the red. The interesting thing is I can see and describe the nebulae just like a "normal" vision person. No one can tell what color it is we all just see light. (We know its red from scientific instruments). This is because at night we (humans) don't use our cone (color) vision, we depend mostly on our rods which can't (see below) perceive color. (bright points of light do activate cones). My rods are like most peoples. There may be other deficiencies that have to do not know of with rods. There is some scientific debate as to how much rods help us perceive color, but I tend to believe they don't help much.

Marty Replied -

Interesting observations.

Dennis wrote -

Well I guess that's all for now. I have learned much about color vision from correspondences like this and I thank you again for responding. I have included a very interesting WEB site on a hearing for a colorblind doctor trying to get his night pilot license. It is probably the most through description I have ever seen on colorblindness.

Marty Replied -

I would like to edit this material and add it to my web page if it is OK with you. I will cut the personal identification references but would like to include the rest.

Please let me know if you agree - I will add you name as the sources, but only if you want me to.