Color Theory Essay, Research Paper
Color photographs begin as black and white negatives. Color film consists of three layers of emulsion, each layer basically the same as in black and white film, but sensitive only to one third of the spectrum (reds, greens or blues). Thus, when colored light exposes this film, the result is a multilayered black and white negative
After the negative images are developed, the undeveloped emulsion remaining provides positive images by “reversal.” The remaining emulsion is exposed (chemically or with light) and the film developed a second time with a different developer. As it converts the light-sensitive silver compounds to metallic silver, the developer becomes oxidized and combines with “coupler” compounds to produce dyes.
The three dyes formed, one in each emulsion layer, are the subtractive primaries yellow, magenta and cyan. All silver is then bleached out and each layer is left with a positive color image.
Thus reds in the subject produce a heavy silver deposit in the red-sensitive layer in the negative, but no trace on the other layers.
Then after reversal, only yellow and magenta remain which together make red. As shown in the illustration, the cyan is all but gone.
After the film is processed and the silver is removed, what remains is called a “Dye Cloud” and as shown in the “enlarged” illustration below the clouds interaction creates a red color.
SUBTRACTIVE COLOR SYNTHESIS uses paints, dyes, inks, and natural colorants to create color by absorbing some wavelengths of light and reflecting or transmitting others. This subtractive action is the basis of photographic filters, almost all films and color papers, and photomechanical reproduction in color.
White light is composed of all visible wavelengths, which can be divided into three primary-color bands, red, green and blue. A colorant that absorbs one wavelength band has the combined color of the other two; it is the complement of the color it subtracts from white light. Thus:
Primary Primary Combined Color Colors Color of the Absorbed Unaffected Subtractive Complementary Red Blue & Green Cyan Green Blue & Red Magenta Blue Red & Green Yellow
The complementary colors are the control colors of subtractive color synthesis; thus, the dyes in color filters and emulsions, and the inks (process colors) used in photomechanical reproduction are cyan, magenta, and yellow. A single complementary produces its own color. Two complementaries in equal strengths produce a primary color because each absorbs a primary–e.g., magenta and yellow absorb green and blue, respectively, leaving red to be seen. Combinations of unequal subtractive strengths produce intermediate colors from white light.
A combination of all three complementaries produces black (full strengths) or gray (lesser equal strengths) because all colors are subtracted. In color filtration this produces neutral density.
Primary-color lights can be additively mixed to produce colors, but primary-color dyes, inks, or filters do not permit selective color control by subtractive action because each absorbs the other two primaries equally. The complementary colors permit subtractive control of each of the three primaries individually; like additive synthesis, this corresponds with the three-color theory of vision.(1)
Color photographic film and paper use subtractive color synthesis to reproduce the real world either directly with transparency film or with an intermediate negative.
Color photographs begin as black and white negatives. Color film consists of three layers of emulsion, each layer basically the same as in black and white film, but sensitive only to one third of the spectrum (reds, greens or blues). Thus, when colored light exposes this film, the result is a multilayered black and white negative.
Color photographic film and paper use subtractive color synthesis to reproduce the real world either directly with transparency film or with an intermediate negative.
Color photographs begin as black and white negatives. Color film consists of three layers of emulsion, each layer basically the same as in black and white film, but sensitive only to one third of the spectrum (reds, greens or blues). Thus, when colored light exposes this film, the result is a multilayered black and white negative.
After the negative images are developed, the undeveloped emulsion remaining provides positive images by “reversal.” The remaining emulsion is exposed (chemically or with light) and the film developed a second time with a different developer. As it converts the light-sensitive silver compounds to metallic silver, the developer becomes oxidized and combines with “coupler” compounds to produce dyes.
The three dyes formed, one in each emulsion layer, are the subtractive primaries yellow, magenta and cyan. All silver is then bleached out and each layer is left with a positive color image.
Thus reds in the subject produce a heavy silver deposit in the red-sensitive layer in the negative, but no trace on the other layers.
Then after reversal, only yellow and magenta remain which together make red. As shown in the illustration, the cyan is all but gone.
After the film is processed and the silver is removed, what remains is called a “Dye Cloud” and as shown in the “enlarged” illustration below the clouds interaction creates a red color.
Transparency film shows this interaction as positive colors and what appears to the eye as grain are in fact dye clouds. Color negative paper also makes dye clouds, though they respond to negative, or subtractive colors, and the interaction of the clouds in the negative combine with the clouds in the paper to reproduce an image. All this softness works to minimize the appearance of “grain”. This is the reason behind the creation of the grainmaker filter.
Screen processes are basic to our perception of the world around us in a variety of communications media, from the dots on your monitor to the pictures you see in magazines. Screens are basically just dots arranged either in a pattern or stochastically (random). A long time ago, photography too, used a variety of screen processes from colored glass beads melted into a glass base to dyed potato starch, as in the autochrome process. All these processes work because the human eye at a certain distance doesn’t see the individual dots but rather perceives their cumulative effect
The most common of the color screen processes is that used for photomechanical reproduction by offset and web presses. Color separation negatives form a rosette pattern, using subtractive color, in addition to black, in a repetitive order to synthesize reality. As you can see from the illustration, the color halftone screens are rotated to form the pattern. These negatives are used to form a image that is “burned” onto printing plates to carry the ink on the press.
By varying the density of the dots color the cumulative effect of say lack of cyan density, gives the appearance of red, by you visually assimilating the combination of the yellow and magenta inks, which in conjunction with the dots small size makes you perceive a continuous tone image with a red color.
Modern color photographic film works by using dyes in the form of clouds (grain) as a stochastic dot reproduction of exposed reality. Old photographic film methods used a variety of screens. One of the earliest was that created by Louis Dufay in France 1910 Called the Dioptichrome plate (aka Dufaycolor,later) which consisted of a mosaic of alternating green and blue dye squares crossed at right angles by a pattern of parallel red dye lines, each element measuring only 0.0002 in (0.05mm) in width. This screen was coated with a panchromatic emulsion, the material was exposed through the base, the screen, and exposing the emulsion from the back. Processed to reversal, the result was a positive transparency. (1) Other methods involved the use of woven fabrics, ruled lines and resists, among others
Additive Color Synthesis is the method of creating color by mixing various proportions of two or three distinct stimulus colors of light. These primary colors are commonly red, green, and blue, however they may be any wavelengths to stimulate distinct receptors on the retina of the eye.
The distinguishing features of additive color synthesis are that it deals with the color effects of light rather than with pigments, dyes, or filters, and that the stimuli come from separate monochromatic sources. The most common example of additive color synthesis is the color television screen, (or RGB monitor), which is a mosaic of red, green, and blue phosphor dots; at normal viewing distances the eye does not distinguish the dots, but blends or adds their stimulus effects to obtain a composite color effect.
This is an enlarged example of additive color synthesis from a RGB type source.
(a) Equal stimulus proportions of two primary colors create a secondary color
1 Red + 1 Blue = Magenta
1 Blue + 1 Green = Cyan
1 Green + 1 Red = Yellow
(b) Equal stimulus proportions of all three primaries create white:
1 Red + 1 Blue + 1 Green = White
(c) Unequal proportions of two or three primaries create other colors:
2 Red + 1 Green = Orange
2 Green + 1 Red = Lime
1 Blue + 1 Green + 4 Red = Brown
All color sensations can be produced this way, including those red-blue mixes (purples and magentas) not found at any wavelength band in the spectrum.
In photography, the principles of additive color synthesis underlie making separation negatives for photomechanical reproduction of color images, and dye transfer and similar printing processes. It was also the principal behind the Autochrome film process and similar screen processes. In the darkroom, additive color printing uses red, green, and blue exposures to obtain prints from color negatives and transparencies. ( 1 ) The Grainmaker filter relies on this principle of additive color printing.
AUHROME was a photographic transparency film patented in America, June 5,1906 (No.822,532) by Auguste and Louis Lumi?re of Lyons, France (FR.Pat.No. 339,223, 1903).
Like other techniques of the time, it employed the additive method, recording a scene as separate black and white images representing red, green and blue, and then reconstituting color with the help of filters. To do this on a single plate, the Lumi?res dusted it with millions of microscopic (avg. size 10 to 15 microns) transparent grains of potato starch that they had dyed red (orange), green and blue (violet). ( 1 ) This screen of grains worked as a light filter to interpret the scene when the light passed through them exposing a panchromatic B&W emulsion. The exposed plate was then processed reversal resulting in a transparency. The illustration below is from their American patent application.
Glass was coated with liquid pitch (def.1) mixed with a small percentage of beeswax (to help keep it “tacky”) then the prepared grain was dusted on. By this very action, the resultant screen was stochastic (or random) in nature. In order to comply with the first black condition (def.2) it was necessary to fill the spaces between the irregularly shaped grains. Lampblack was used as a filler, applied by way of a special machine. The result is shown in the “enlarged” illustration below
The starch was probably (facts are a bit sketchy) dyed using triphenylmethane dyes (note 1) to achieve a color wavelength of between 550 to 670 for the red, 470 to 570 for green, and from 430 to 520for the blue.
Later, the Lumi?res discovered the transmission quality of the plates could be improved by applying pressure (5000Lbs. per sq. inch (3) to the composite prior to the addition of lampblack. Potato starch grains are not flat, but somewhat rounded, and in my opinion, their method of elutriation (def.3) contributed to the puffy condition of the starch.
The next stage in construction was to coat the composite with liquid shellac to totally encapsulate the grain layer (in essence, forming an envelope of amber around the grain).
After drying, the panchromatic B&W emulsion was then coated on the composite plate and the final plate was soon ready for market.
The plate was exposed in a glass plate type view camera by placing it in the holder with the coated side away from the lens, so that when exposed, the light traversed the glass, through the grain and exposed the light/color sensitive emulsion from the back. After exposure, the plate was processed to reversal in an acid dichromate type process.
The final photograph has a beautiful look with wide tonal gradation and if you could see an original well preserved Autochrome today, you would be amazed at the extrodinary way they age, and can in fact appear as though they were processed only yesterday. The image below is an original Autochrome, photographer unknown.
This filter is the only one of it’s type in the world. Used for introducing the appearance of enlarged grain in color photographic prints. The appearance of grain created is a true representation of the color inherent in the original.
Unlike texture screens that work by breaking up the image using a patterned blocking mask such as Kodalith film (tm ? Kodak), this process works by projecting a “normal” photographic color negative thru a handmade “additive color synthesis” stochastic screen comprised of millions of grains of transparent potato starch. The starch is dyed to two specific wavelengths then mixed to uniformity and coated on a glass plate.
Printing is achieved by utilizing a custom glass carrier for enlarged grain imaging or projected thru a coated glass plate that is in contact with a receptor paper. From subtle to radical effects are possible, while maintaining the contrast of the original and the ability to control color. To learn how this process was invented and how we make it, go here.
The Grainmaker color filter system was designed to introduce the appearance of grain in color photographic prints by using dyed transparent potato starch coated on a glass plate as a filter through which a color negative is projected. Several steps are involved in its construction as outlined below.
The first step is to size the starch; I use a pharmaceutical raw product service to separate the starch down in size to 15 microns or less because the larger grains are unsuitable for this use. The dyes used are commercial and pharmaceutical varieties of triphenyls. (food coloring will not work) The starch is dyed using an air driven device to blow the dry starch into a continuously agitated container of liquid dye kept at a temperature of 90 F until its the consistency of syrup. (The starch must be blown in or else it dyes unevenly.) The wet starch is then poured into trays to dry. Several days later, the dry starch is pulverized and re-filtered, then mixed to uniformity in a baffled tumbler
The colors used are very important and as shown in the “enlarged” illustration the colors are cyan/green and yellow/green in nature. Through a number of tests I determined these colors worked the best with color negative paper to yield a neutral gray with direct enlarger exposure. If you can achieve a neutral, all colors are possible within the limits of the material.
As you can see, I chose not to fill the interstices with lampblack for two reasons, first, I don’t have access to any drawings on the construction of the special machine used by the Lumieres in their autochrome process, and second, it seems to work fine without it.
The next step is to prepare the glass by using a machine of my design to cover the plate evenly with a custom made adhesive as shown in the illustration below.
By passing the knife blade (yellow) over the adhesive spreads it evenly, then the wet plate is attached to a centrifuge and spun at 1000rpm to smooth it out, its then left to dry for several days until the adhesive sets up. Finally the mixed grain is dusted on, and it receives a coating of epoxy sealer. The plate is now ready for use.
The plate is inserted into a glass carrier grain side up and the color negative is placed in this modified carrier in the usual way. The print is made by projection through the screen resulting in the appearance of natural grain, only more so.
COLOR is a phenomenon of perception not an objective component or characteristic of a substance. Color is an aspect of vision; it is a psychophysical response consisting of the physical reaction of the eye and the automatic interpretive response of the brain to wavelength characteristics of light above a certain brightness level (at lower levels the eye senses brightness differences but is unable to make color discriminations). ( 1 )
That light is the source of color was first demonstrated in 1666 by Isaac Newton, who passed a beam of sunlight through a glass prism, producing the rainbow of hues of the visible spectrum. This phenomenon had often been observed before, but it had always been related to latent color that was said to exist in the glass of the prism. Newton, however, took this simple experiment a step further. He passed his miniature rainbow through a second prism that reconstituted the original white beam of light, His conclusion was revolutionary: color is in the light, not in the glass, and the light people see as white is a mixture of all the colors of the visible spectrum. ( 2 )
The reason rainbows appear colored is because the light is broken down into its constituent parts by passing through the water droplets in the air. (Sorry, no pot of gold. The perception of color in a rainbow is proportional to the viewer’s perspective, you move, it moves.)