We've been trying to make "purple" at work. We are playing with RGB LEDs and between three engineers and a printer we have found that we have a subjective idea of colours, except our printer friend who insists that there is a Pantone number that would apply.
Why mention this? The follow up post on the coloured cube illusion used CYMK colours. I find this strange when an LCD is in the RGB domain, and I tend to think of CYM as secondary colours.
"The CMYK values are just the RGB values converted to CMYK. The writer doesn't understand colour."
I used to think so, too. Until the day I designed something to be printed on an offset press. Now I know that every color space has its own gamut, and that the conversion can be very disappointing.
There are numerous other color systems used by various industries to specify colors (plastics, automobile, etc.). The perceived color also depends on numerous and often hard to define factors, such as surface reflectivity and specularity, etc. Not to mention context, as the subject of this post eloquently demonstrates.
Some people however appear to have a more accurate color perception. My sister, for instance, will look at tiny specks of color in the upholstery, and then later pick the exact same color out of hundreds of swatches at the hardware store. And she does so with an astounding success rate, I might add (she still gets it wrong at times). I wish I could do that...
Of course the CMYK gamut is different! I wrote a PostScript interpreter from scratch for god's sake, I know what I am talking about.
I meant that the CMYK values mentioned by the author of the blog post are nothing but RGB converted to CMYK (a service automatically provided by any standard image editing application). What he is really referring to is RGB colour (the jpg image is in RGB), but he is naïvely presenting the reader with the CMYK converted value of it. RGB values can be converted to CMYK by a simple mathematical formula.
Yes, I know about the the other colour spaces. We supported many of them in our PS interpreter. Also, about reflectivity and specularity, different halftone screening algorithms for different paper stock etc.
My point is that you are unnecessarily complicating the issue with regards to the optical illusions Eolake posted about. CMYK does not factor in here even though the poster misleadingly talks about "CMYK".
When I was a kid we only cared about primary colours of pigments, red, blue, yellow. When I started in on physics I switched to thinking RGB. I couldn't help but notice the CYM & black patches on the tabs of cereal boxes, and learnt about printing colours.
Everyone works in their own color space, as I said, I know people who think pantone, others now the X11 colours. I just happened to be in a very RGB space at the moment. Vive la difference.
I know! He said (and Im recalling from a memory now more than 10 years old, so pardon me if I get some of this wrong) that we dont actually look at the orange but rather at the light reflected back at us from the orange. If we were to eliminate all the light and our perception of it then the orange, in its natural state, would be blue.
Sounds ridic. Color is only a property of light, so if you eliminate light obviously color does not exist.
I'm reminded though of a classic Superboy story which had blue bananas in it. I think they were from the Phantom Zone or some alternate universe. In Denmark the story was printed in B/W, so the joke was a bit lost.
I can see how an orange, only absorbing blue light, reflects everything else. However, we normally describe an item by the light reflected, not the light absorbed.
Does this mean wode is orange.
One of the fun things about light, having a lamp change from red to green to blue, it makes everything around it go weird. For example the red clip lead that was powering the unit alternated between black and red. It's 3-d glasses all over again.
alex said: "However, we normally describe an item by the light reflected, not the light absorbed."
Correct. But leviathud's painting teacher's viewpoint does pose an interesting philosophical question:
If the object absorbs (i.e. keeps) the blue, and reflects (i.e. rejects) the rest of the visible spectrum (red + yellow = orange), what is the object's identity when expressed as a colour?
If you answer orange, there's one additional question:
Ah, but also can't light energy of one frequency be absorbed, and then released as a different frequncy, as in phosphorescent material.
This is how white LEDs work, they are typically a UV LED with a white phosphor. The UV spectrum is converted to a broader blend of lights. This is also how some laundry detergents work.
I actually meant things other than the orange. The orange probably does the heat thing, but things that are not oranges can do other things, like phosphors.
Cos-play. It's a 1980's fireman's uniform. I believe in the white helmets came later. The full image is here. Looks like this uniform appeared around 1981, the older vintage was silver belt and yellow buttons. Then they had a fire logo on the breast pocket in the 90's. Todays firemen have the reflective jackets, and look almost real. Peeron have a good selection of fire chiefs depicted.
The Theory of Relativity should always be taken with a G.R.A.I.N. O.F. S.A.L.T. (General Relativity Accepts Infinite Nuances, Open Field, Still Assessed Lightly Today)
20 comments:
We've been trying to make "purple" at work. We are playing with RGB LEDs and between three engineers and a printer we have found that we have a subjective idea of colours, except our printer friend who insists that there is a Pantone number that would apply.
Why mention this? The follow up post on the coloured cube illusion used CYMK colours. I find this strange when an LCD is in the RGB domain, and I tend to think of CYM as secondary colours.
The CMYK values are just the RGB values converted to CMYK. The writer doesn't understand colour.
"The CMYK values are just the RGB values converted to CMYK. The writer doesn't understand colour."
I used to think so, too. Until the day I designed something to be printed on an offset press. Now I know that every color space has its own gamut, and that the conversion can be very disappointing.
There are numerous other color systems used by various industries to specify colors (plastics, automobile, etc.). The perceived color also depends on numerous and often hard to define factors, such as surface reflectivity and specularity, etc. Not to mention context, as the subject of this post eloquently demonstrates.
Some people however appear to have a more accurate color perception. My sister, for instance, will look at tiny specks of color in the upholstery, and then later pick the exact same color out of hundreds of swatches at the hardware store. And she does so with an astounding success rate, I might add (she still gets it wrong at times). I wish I could do that...
Of course the CMYK gamut is different! I wrote a PostScript interpreter from scratch for god's sake, I know what I am talking about.
I meant that the CMYK values mentioned by the author of the blog post are nothing but RGB converted to CMYK (a service automatically provided by any standard image editing application). What he is really referring to is RGB colour (the jpg image is in RGB), but he is naïvely presenting the reader with the CMYK converted value of it. RGB values can be converted to CMYK by a simple mathematical formula.
Yes, I know about the the other colour spaces. We supported many of them in our PS interpreter. Also, about reflectivity and specularity, different halftone screening algorithms for different paper stock etc.
My point is that you are unnecessarily complicating the issue with regards to the optical illusions Eolake posted about. CMYK does not factor in here even though the poster misleadingly talks about "CMYK".
When I was a kid we only cared about primary colours of pigments, red, blue, yellow. When I started in on physics I switched to thinking RGB. I couldn't help but notice the CYM & black patches on the tabs of cereal boxes, and learnt about printing colours.
Everyone works in their own color space, as I said, I know people who think pantone, others now the X11 colours. I just happened to be in a very RGB space at the moment. Vive la difference.
Speaking of colour, my painting teacher said that an orange is actually blue. I dont think I've ever recovered.
Wow.
I know! He said (and Im recalling from a memory now more than 10 years old, so pardon me if I get some of this wrong) that we dont actually look at the orange but rather at the light reflected back at us from the orange. If we were to eliminate all the light and our perception of it then the orange, in its natural state, would be blue.
Sounds ridic. Color is only a property of light, so if you eliminate light obviously color does not exist.
I'm reminded though of a classic Superboy story which had blue bananas in it. I think they were from the Phantom Zone or some alternate universe.
In Denmark the story was printed in B/W, so the joke was a bit lost.
She must have meant that the object absorbs blue. This means it then reflects red and yellow (= orange).
Blue and orange are complements.
I can see how an orange, only absorbing blue light, reflects everything else. However, we normally describe an item by the light reflected, not the light absorbed.
Does this mean wode is orange.
One of the fun things about light, having a lamp change from red to green to blue, it makes everything around it go weird. For example the red clip lead that was powering the unit alternated between black and red. It's 3-d glasses all over again.
Oh, great, while I was composing TTL actually posted about absorption. Now I look like I just copied him.
alex said: "However, we normally describe an item by the light reflected, not the light absorbed."
Correct. But leviathud's painting teacher's viewpoint does pose an interesting philosophical question:
If the object absorbs (i.e. keeps) the blue, and reflects (i.e. rejects) the rest of the visible spectrum (red + yellow = orange), what is the object's identity when expressed as a colour?
If you answer orange, there's one additional question:
What happens to the blue -- where does it end up?
As heat.
Ah, but also can't light energy of one frequency be absorbed, and then released as a different frequncy, as in phosphorescent material.
This is how white LEDs work, they are typically a UV LED with a white phosphor. The UV spectrum is converted to a broader blend of lights. This is also how some laundry detergents work.
Wikipedia has more to say on LEDs in the flouresence page which is linked from the phosphorescence page
You are absolutely right. Although I will claim for my defense that I have never seen a fluorescent orange (the fruit, that is).
Mind you, I vaguely recall a Tintin album where it was question of blue oranges, but I don't recall if those were fluorescent. ;-)
I actually meant things other than the orange. The orange probably does the heat thing, but things that are not oranges can do other things, like phosphors.
Of course, and you were very clear about that, no need to get ready for a trench war! Or is there another reason for the grand uniform?
Cos-play. It's a 1980's fireman's uniform. I believe in the white helmets came later. The full image is here. Looks like this uniform appeared around 1981, the older vintage was silver belt and yellow buttons. Then they had a fire logo on the breast pocket in the 90's. Todays firemen have the reflective jackets, and look almost real. Peeron have a good selection of fire chiefs depicted.
The Theory of Relativity should always be taken with a G.R.A.I.N. O.F. S.A.L.T.
(General Relativity Accepts Infinite Nuances, Open Field, Still Assessed Lightly Today)
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