Submitted For Your Approval --C&C please

[ggt]

I've been confused a bit over the difference between color as pigment and color as light. In the past I've always used a pigmented media, now with photography, the media is light. In pigment, all the colors mixed together make gray, in light, they would make white --and so on . . .

I've pulled my resources and decided what I have is basically a vocabulary issue. As I am a visual learner:



Please tell me if you think I have any of the words in the wrong category or if the diagram is off. Also, with the words "Warm" and "Cool", in photography do they refer to the value or wavelength (hue)

thanks for your support!

[Manfred M]

Grtechen - there are essentially two colour models:

1 Additive - this is what we see when we look at our computer screens or televisions. Three colours are transmitted - Red, Blue and Green (RGB) light sources combine to make white. Black is simply the absence of any colour; and,

2. Subtractive - this is what we get in any printed media, paints, etc. An external source illuminates the object and light is reflected back. When all wavelengths are reflected back, we see white. When we see black, all light is absorbed and no light is reflected back. The purest form is printing (photographic or otherwise), when the base material is white (i.e. the paper) and inks are applied to absorb light. In theory the three subtractive colours are Cyan, Magenta and Yellow, but because inks are not perfect, combining these three colours actually results in gray. In printing black ink is added to compensate, so we get CMYK. The "K" stands for "Key" which comes from the colour printing press. The black plate is referred to the key plate and the C, M and Y colour plates are aligned or keyed to the plate.

These are probably the two colour models that are easiest to understand, but there are other ways of describing colour as well. The Munsell model is just another way of describing colours, as per your diagram. There are several other varients as well, like HSL (Hue, Saturation, Lightness) and HSV (Hue, Saturation, Value). HSL looks at colours much the same way Munsell does.

[John Morton]

Hi, Gretchen;

I like your use of a Mobius strip for your illustration!

I was reading an article in a artist's magazine recently about a painter who is noted for his still life paintings of flowers. One thing he mentioned is that he dilutes his pigments into washes to get luminous colors - as opposed to adding white. That would be the difference between saturation and brightness: a diluted wash on white paper would give a saturated, more luminous color (say, an intense red); whereas a red mixed with white would give a brighter color - in this case, a pink.

The diluted color allows more of the base under color, the white paper for instance, to reflect more fully the light striking it; and that is always how colors work with printing. It's a little different than the case with pigmented paints, which themselves reflect colors but actually the principle is the same - everything but the color seen is absorbed.

Printing is done with CMYK inks sets: Cyan absorbs red light; Magenta absorbs green light; and Yellow absorbs blue light. So, moving from digital Red Green Blue sensors and monitors, printing on paper just involves using ink that absorbs the colors you DON'T want to show - leaving the RGB color you do want to be reflected from the white paper. K is just black ink,, added because CMY alone only gives a dark muddy brown. Interestingly, black ink wasn't used this way for commercial printing until sometime in the 1960's, I think; so if you've ever seen photographic illustrations in magazines from the 1940's and 50's, and thought that the pictures looked kind of 'flat', that's why - they weren't using black ink back then, just a mix of CMY. Conversely, if you see an option to 'print text as Rich Black', this will add CMY inks to the black ink usually used for text - to give a deeper, richer black color to the text.

Saturation in an RGB histogram corresponds to the height of the value; brightness corresponds to the location, left (darker) or right (lighter).

In physics, cooler temperatures produce redder colors and hotter temperatures produce bluer colors. This is because red light has a longer wavelength (think 'infrared') and blue light has a shorter wavelength (think 'ultraviolet'); so there is more energy packed into the same space for blue light (shorter waves = more of them in the same space) than red light (longer waves = fewer of them in the same space).

Less energy means lower temperatures are needed to excite atoms giving off those wavelengths; more energy means hotter temperatures produce those wavelengths. These temperatures are given in degrees Kelvin: a specific color temperature in degrees Kelvin is like a balance point, the white balance where light appears white for that temperature. Anything below looks more reddish; anything above looks more bluish.

You can actually see this correspondence in charts that compare the light emitted by stars, some of which are hoter and some of which are cooler than our sun:

http://www.atlasoftheuniverse.com/hr.html

This chart shows the color of stars, from hot blue on the left to cool red on the right; with degrees Kelvin across the top of the chart. There is a reason that the cooler, redder temperatures are on the right; and it has to do with the way that the rest of the information about the star's size (absolute magnitude) and distance are calculated (which is really quite elegant).

Longer wavelengths are redder; and light from a source that is moving away from us are stretched out so they look redder than they should be. By the same token, light from a source that is moving toward us is compressed, so, it looks bluer. Now, since stars spin, the light from the edge that is spinning away from us is shifted slightly toward red; and the edge spinning toward us is shifted toward blue. We can tell how hot the star is by the elements that are emitting light within it; and we can tell how big it is by how fast it is spinning, using the difference between the blue and the red shift of the spectrum for the elements emitting light within the star. Since we know how hot it is (from the emission spectrum) and how big it is (from the spectral shifts), we can them determine how far it is by the apparent luminosity (how bright it appears to us); and this lets us determine an Absolute Magnitude (how bright the stars would seem relative to each other if they were all the same distance away from us).

So, it seems more natural (to astronomers, anyway) to put the red end of the chart on the right and the blue on the left, even though this means the chart runs from hotter to cooler (because that is also, sort of, 'from nearer to farther'); although if the chart had been invented by astronomers who used a language where they read from right to left, that might have been reversed.

In color theory and fashion (which has been around much longer than instrument-based astronomy and spectrography), 'warm' colors are ones associated with fire - reds, oranges, yellows - and 'cool' colors are ones associated with water and ice - blues, and I guess greens too. That is just the opposite of the meanings for those words in physics; but of course both uses come together in photography, even though they are exactly opposite.

[ggt]

Grumpy, thanks. I like your example of the TV vs Printed media. That is a good representation. I use the Munsell Chart because as a Freshman in College we had to make our own --a grueling and all together stupid exercise with which they torture students. As a result, it is what I know best and attempted to understand any other requires that I first compare and contrast it with Munsell. UGH!!!

Thanks for your input, it does help.

[ggt]

John, you give the best explanations--of course, that means my eyes glaze over 1/2 way thru and I have to print and actually study what you have written. Are you a teacher??? LOL

Thanks for taking the time, it does help.

The color temperature concept had me confused for a while. I figured it was a game of opposites and your explanation confirmed my suspicions. I may have to ignore this part of color theory until I grow-up.

Thanks again!

[John Morton]

Hi, Gretchen;

Sorry - I got a bit carried away there - but not until about 1/2 way through so you've got the important bits!

[Manfred M]

The color temperature concept had me confused for a while. I figured it was a game of opposites and your explanation confirmed my suspicions. I may have to ignore this part of color theory until I grow-up.

The physics and the creative sides do not look at colour the same way. John is absolutely correct regarding the energy levels of the photons, where the shorter wavelengths have higher energy. This distinction is very important when setting the colour temperature settings of our cameras when we shoot jpegs (for RAW, it has no impact at all as we set the colour temperature in PP, so it does come into play at that stage). It seems rather counter-intuitive that the colour temperature at high noon in the middle of the snow covered mountain range is higher than the warm glow of the setting sun in the tropics. Yes, you need to understand this technical aspect of photography, that's physics part and has absolutely nothing to do with artistic side of photograhy.

The reds, oranges and yellows, i.e. the warm tones in an image have a totally different impact than the blues, greens and purples, i.e. the cool tones; that's the artistic side. The confusion comes from the fact that the same word is used to describe two totally different aspects of photography and as long as you understand that, it is not too hard to deal with.