The color purple

[JDMvW]

Reds into purple were tough for film and even for digital.

Here are a 'bunch' of those colors taken on Fuji color film with a Canon VL2 with an Industar-61 Soviet lens.

Edited June 22, 2023 by JDMvW

[Alan Marcus]

Color photography is rooted in mixing varying proportions of the three light primary colors. We use red, green, and blue, the additive primaries. Such a system generates all of the spectrum colors, however spectrum colors are only approximated whereas most ordinary colors can be matched exactly. Now purple and magenta do not appear in the spectrum, however they too are produced approximately via this system.

After the picture is taken, it must be somehow presented to our eyes. We us the additive system for TV and computer display but photo films and prints are best when a subtractive system is used. Both systems fracture the picture into super tiny elements. We are talking about pixels (picture elements) the smallest fraction of a picture that can convey intelligence.

The additive system adjusts the proportions of red, green, and blue that reach our eye by controlling the relative intensities of red, green, and blue as displayed on a TV or computer screen. The subtractive system uses the complements (opposites) of red, green, and blue which are cyan, magenta, and yellow.

The density of the cyan dye controls the amount of red light that reaches our eye. The magenta dye controls green and the yellow dye controls blue. These work together to control the amount of red, green and blue light that reaches the eye.

Keep in mind that modern color films are complex. All are basically black & white film infused with colored dye. These films are silver-gelatin blends. Salts of silver react to light and when exposed become developable. The developer seeks out exposed silver salt crystals and reduces them to metallic silver and a soluble component. The metallic silver forms a black & white image of the vista.  

Cyan, magenta, and yellow dye are also included in this mix. The dyes used are incomplete. The three are missing a single needed ingredient which is in the developer. In other words, they are in a Leuco state (Latin for white or blank). The waters of the developer contain dissolved oxygen. As developing proceeds tiny tuffs of metallic silver, making up the image, form. The metallic silver is speedily attached by oxygen. This is the catalyst that causes the missing dye ingredients to unite with the Leuco dye. The dye blossoms forming the color image. They silver image conceals the color image. The silver will be afterwards removed.

Finding cyan, magenta, and yellow dye that are Leuco and all missing the same ingredient is a challenge. The problem has never been satisfactorily solved. The yellow dye we use is OK, the magenta dye is fair, the cyan dye is poor. In the negative process, the poor cyan and magenta dye can be alleviated by giving them a warm tint that dissipates when they fully blossom. This forms the orange coloration you see in negative films. The two residual warm tints form two positive corrective images superimposed over the three negative images.

Bottom line, to this date we have never been able to make a film or photo paper that yields a faithful image of a vista. The compromise is to make film and photo papers that deliver good facial tones. To this end, some color matching is forfeited.      

[JDMvW]

As always, thanks Alan.

 

I very much recommend

Margaret Livingstone 2014 Vision and Art.