On Mixing Colors of Light

[sophiecentaur]

I found the color picker. I'm still working on it though to get color coordinates etc. The software is not self-explanatory.

It was a long time ago that I used GIMP but I seem to remember a little 'dropper' icon which breaks out a magnified sample of the image (on the mouse position) it shows the RGB values of the central pixel. A CIE chart is interesting to scanover with the dropper.

 

[Charles Link]

It was a long time ago that I used GIMP but I seem to remember a little 'dropper' icon which breaks out a magnified sample of the image (on the mouse position) it shows the RGB values of the central pixel. A CIE chart is interesting to scanover with the dropper.

I'm starting to figure it out thanks. If you work with RGB, those are each numbered 0 to 255, but as you change those, it changes the other values in the display, like CMY, etc.

See https://fixthephoto.com/online-gimp-editor.html

 

[sophiecentaur]

but as you change those, it changes the other values in the display

What does that mean? As you move between areas on the CIE chart, why shouldn't more than one value change?

Did you notice that there are very few objects in a scene with one of RGB being near zero? Saturated colours are rare in everyday scenes.

 

[Charles Link]

See https://fixthephoto.com/online-gimp-editor.html

I'm still working on it, but I'm beginning to figure it out. :)

 

[Charles Link]

I've gotten very little feedback from the section on page 3 of posts 75-78, ( just one person responded there), but I think a couple readers might find that section of interest. Using the software in the link in post 75, it is easy to show that my original post, the OP, is indeed what you can get, with the one correction being that the yellow is from around 580-590 nm, rather than at 600 nm.

 

[sophiecentaur]

a couple readers might find that section of interest

Did you consider that what you are saying may not be as 'right' as you think it is.? After a lot of posts between you and me, you still don't seem to have taken on board what I have been saying. You just seem to ignore very important points that I have made. Your terminology and basics are still the same as when you started on this thread. You have to allow yourself to have your ideas changed but I get the feeling that you just don't want to be wrong. Just 'bending' what you read here to fit your ideas won't get you anywhere.

 

[Charles Link]

Did you consider that what you are saying may not be as 'right' as you think it is.? After a lot of posts between you and me, you still don't seem to have taken on board what I have been saying. You just seem to ignore very important points that I have made. Your terminology and basics are still the same as when you started on this thread. You have to allow yourself to have your ideas changed but I get the feeling that you just don't want to be wrong. Just 'bending' what you read here to fit your ideas won't get you anywhere.

It is certainly possible it isn't completely correct. The CIE coordinates and their vector space assume a linearity of the human response, and in that sense it isn't a perfect model. Using the CIE map though, what I proposed in the OP and post 75 is in agreement.

Perhaps I would do well to move onto some other topic though. The E&M with its vector calculus and things like magnetostatics might be worth revisiting, but that will have to be in some other new thread= and there is always the possibility that I erred in the computation of the addition of a couple of simple vectors, (in posts 75-78), but do you know that $\nabla ( a \cdot b)=a \cdot \nabla b+b \cdot \nabla a +a \times \nabla \times b+b \times \nabla \times a$ ?, (where $a=\vec{a}$ and $b=\vec{b}$), a vector identity that can be useful in some E&M work. I don't know everything either, but I do try to make the posts somewhat interesting. Hopefully I didn't bore you too much. Cheers. :)

 

[DaveC426913]

Something that I only recently cottoned on to is that, in the early days, camera film had really bad red sensitivity so spectral measurements had very little information about red (or IR). The universe looked very different in them thar days.

That's also why darkrooms are lit with red light, even in TV and films. The photo paper is insensitive to far red, though we can can pick it up with our eyes.

 

[sophiecentaur]

That's also why darkrooms are lit with red light, even in TV and films. The photo paper is insensitive to far red, though we can can pick it up with our eyes.

Very historical. I can’t bring myself to ditch my old film cameras but it wasn’t a good medium.

 

[DaveC426913]

Very historical. I can’t bring myself to ditch my old film cameras but it wasn’t a good medium.

Still got my Pentax K-1000 from college.