PDA

View Full Version : Color Theory Question



Mustafa Umut Sarac
08-02-2011, 01:25 PM
If I have the RGB Curves for example of Kodachrome. How I can know how these RGB or CMYK curves works together. Is there a more detailed , 3D representation of it.
Or a color mix function ?

Thank you ,

Umut
Istanbul

Bob Carnie
08-02-2011, 01:32 PM
K is a black channel, you must mean cmy and rgb, I will ponder this question and may have to ask Dinesh my mentor this question.

If I have the RGB Curves for example of Kodachrome. How I can know how these RGB or CMYK curves works together. Is there a more detailed , 3D representation of it.
Or a color mix function ?

Thank you ,

Umut
Istanbul

Mustafa Umut Sarac
08-02-2011, 01:36 PM
Indian Guru Dinesh , Save my sprit :)

domaz
08-02-2011, 03:01 PM
Maybe Gamutvision (http://www.gamutvision.com/)?

Monito
08-02-2011, 03:45 PM
If I have the RGB Curves for example of Kodachrome. How I can know how these RGB or CMYK curves works together. Is there a more detailed , 3D representation of it.
Or a color mix function ?

Yes, it is colour mixing. Kodachrome is slide transparency film. So transmitted colours are mixed.

In a colour monitor, Red, Green, and Blue light (relatively narrow bands of frequencies) are mixed to make colours, because transmitted colour is Additive. We perceive Yellow when Red and Green light are mixed. We also perceive Yellow when light in the yellow frequency range is radiated. This means that there are several combinations available to produce many colours. This is called "metamerism" and uses "metamers".

In printed material, colour is reflected and so it is subtractive. Yellow is part of the CMY primary colours. It reflects yellow light. Just how that is constituted depends on the actual ink used.

In a transparency film, colour is produced by filtration, so it is subtractive. The filter subtracts (blocks) light. White light has all frequencies (all colours). The white light of the light table or projector is filtered by the slide. Where the Yellow layer and the Magenta layer are both present (have Y and M tones in that area) they together filter out light to give the perception of Red.

Leigh B
08-02-2011, 05:24 PM
Perhaps understanding the relationship between CMY (Cyan/Magenta/Yellow) and RGB (Red/Green/Blue) would help.

White light is composed of Red, Green, and Blue light.

If you remove the Red, you end up with Green + Blue which equals Cyan, so Cyan = minus Red
If you remove the Green, you end up with Red + Blue which equals Magenta, so Magenta = minus Green
If you remove the Blue, you end up with Red + Green which equals Yellow, so Yellow = minus Blue

This is how filters work.

If you look at a white light through a Magenta filter, you see Red plus Blue, which is called Magenta.
If you then add a Cyan filter, so you're looking at the light through both filters one on top of the other, you only see Blue, because the Magenta subtracts the Green, and Cyan subtracts the Red.

This is the way color slide films work. The filters in an enlarger color printing head work the same way.

- Leigh

BTW, the reason the Black (K) channel is added to form CMYK is that you can't get a clean black by combining the three subtractive primaries.

Mustafa Umut Sarac
08-02-2011, 05:39 PM
My question is totally different. For example , autochrome , there are 6 different colors at the filter. I ve posted the dyes. Dyes have a spectrum curve. And there is a published only RGB curve analysis of Autochrome.
How can we calculate from these dye curves or RGB curves , how a RGB xyz color transforms at the film x2y2z2.
And how can we see this transform at a graphic.

Above posted software link , may be relates with this question but I dont know it solves the problem

Julia
08-10-2011, 06:26 PM
If I have the RGB Curves for example of Kodachrome. How I can know how these RGB or CMYK curves works together.

Those are density curves, right? To interpret those in a regular colour space (say, Lab), you need to know the spectral properties of the dies.

Leigh B
08-10-2011, 06:47 PM
Perhaps you meant 'dyes'. :D

- Leigh

Diapositivo
08-10-2011, 07:40 PM
Actually it must be "dies", is more "spectral" ;)

wildbillbugman
08-11-2011, 04:09 PM
Dyes can make you die, if you ain't carefull!

DREW WILEY
08-12-2011, 03:41 PM
Color space can be based upon either a three-dimensional or four-dimensional axis model. There are probably a number of commercial services and software programs marketed for this purpose. The basic
simplified ones which merely relate screen to printer output would be inadequate. Rather, someone would have to isolate every specific dye or pigment used in a particular medium and plot this with a continuous spectrophotometer, then map the gamut space. But I fail to see what value the result would be unless
you have already studied color mapping and understand the implications. Breaking down the values for
an obsolete color process would be quite difficult unless you have adequately sized samples of each
primary component.