Colour technicalities (1)

In preparation for Assignment 4, which will include a brief discussion of colour palettes, I felt that I needed to understand more about colour theory as it relates to photography. I have therefore studied the entire chapter entitled Color (Suler & Zakia, 2018: 141-182). These notes summarise my learning from pages 141 – 152 – as much as I can take in in a single dose!

Initially, I found the chapter mind-boggling as I had no idea that there was so much to colour! However, studying it has given me an initial understanding of some of the key concepts and has enriched my vocabulary.

The purpose of these notes is to help me to better understand and remember these concepts and to set out some of my own thinking in relation to them.

Basic terminology

• Hue = what we generally call colour
• Saturation (also called chroma) = intensity or purity of a colour – determined by how much grey is added to it
• Lightness (also known as brightness, value or tone) = degree of brightness of an image, determined by how much white or black is added to it

“Color is a visual experience dependent on light” (Suler and Zakia, 2018: 143). This is such a vital consideration for the photographer (and indeed, the painter – as the Impressionists well understood) and explains why the same object or scene may appear to be different colours under different lighting conditions – it is not the colour of the object or scene that has changed, but the quality of the light. The quality of light is affected by many different factors, some of which are discussed further below.

Colour notation systems

“Physical measurements such as distance, temperature and time are relatively easy to make. They do not require a human observer. Color measurements are a different matter. Color is a visual experience dependent on a human observer, as is the perception of sound, smell, taste and touch.” (Suler and Zakia, 2018: 143)

Although on one level, this is obvious, it also brought home to me the degree to which the perception of colour is a subjective matter. The subjective response is nevertheless mediated by the quality of light (an objective measure). These objective measures include, for example, temperature, discussed further below.

Because of the subjective element, “Color can be measured in a number of ways; the most sophisticated being psychophysical measurements such as those used in the CIE system. Such measurements include a human observer.” (Suler and Zakia, 2018: 143)

One of the earliest standardised notation systems for colour is the Munsell system (1905) which classifies colours by three variable: hue, value and chroma (as defined above). The Munsell Color Tree can be found here.

The notation system indicates the hue, then the value, then chroma (in that order), so “Green 4/5” would specify a green hue with a value of 4 and a chroma of 5. A darker green would be “Green 3/5” and a lighter green “Green 5/5”. The hue and chroma remain the same, but the brightness differs.

The Munsell System is based on equal colour differences – i.e. the intervals between the colours are visually equal in adjacent hue, value and chroma.

Pantone Color Formula Guide is a colour naming system for printing inks, similar to colour swatches found in paint shops. There are more than 1,000 Pantone spot-colour ink mixtures, each with it’s own number for ease of reference. This aids communication with printers. Pantone also has available Pantone Matching System Colours for the Web. See also. http://www.pantone.com

“In 1931 the CIE system of color specification became an international standard for colorimetry – the measurement of color.” (Suler and Zakia, 2018: 146)

CIE = Commission Internationale l’Eclairge (International Commission on Illumination)

“Color specification with the CIE system differs from that of the Munsell system in that a mixture of red, green, and blue light is used in varying amounts to match a given sample… The observer views the colours through a small aperture. The colours viewed are not surface colours but rather aperture or film colors. They have no surface characteristics.” (Suler and Zakia, 2018: 146)

The numerical data derived from a large number of matched samples are mathematically manipulated and transformed into a graphic representation the CIE Chromaticity Diagram:

Chromaticity refers to two of the three attributes of colour: hue and chroma. These are plotted on a graph and indicated numerically by the wavelength of the colour. (Wavelength is measured in nanometers. When all colours are plotted, this makes a horseshoe shape. I found a good video which explains in more detail here.

“By plotting a large number of different colours that an imaging system such as a printer or screen can reproduce, a range of colours called a gamut can be mapped within the horseshoe corral. In this way, it is possible to compare the gamut of colors that can be reproduced by various imaging systems. For example, different colorants C, Y, M, K (cyan, yellow, magenta, black – dyes, inks, toners) or R,G,B phosphors (red, green, blue) can be tested to see if they extend the gamut of colors a particular system can reproduce.”(Suler and Zakia, 2018: 147)

Gamut = the complete range of things (colours).

Phosphors = light emitters.

At this point, I began to understand why a printed image (C, Y, M, K) may have a different colour appearance to the ‘same’ image viewed on a computer screen (R, G, B). I regard this as a hugely important learning point for me, and absolutely critical to understanding print photography. All at once, I understand why the printed photographs in my collection of Wildlife Photographer of the Year books look nowhere near as vibrant as seeing them ‘for real’ in the exhibition space where the images are shown on screens.

In my own words: print images are produced using a blend of C, Y, M, K inks whereas digital and film images get their colour from R, G, B phosphors.

Luminance (value and brightness)

“The CIE diagram is for just one level of luminance, for every other level of brightness, another two dimensional map would be needed.” (Suler and Zakia, 2018: 147-8)

Luminance depends to a large degree on the light source and the CIE has classified standard light sources and their correlated colour temperatures (CCTs). In photography, this has an important bearing on white balance. Some of the standard CIE illuminants are:-

CIE illuminant A	2856K	Kelvin
CIE illuminant C	6774K	Daylight (CCT)
CIE illuminant D65	6504K	Daylight (CCT)
CIE illuminant D50	5003K	Daylight (CCT)
CIE illuminant F2	4230K	Cool-white fluorescent (CCT)
CIE illuminant F8	5000K	Fluorescent (CCT)
CIE illuminant F11	4000K	Triband fluorescent (CCT)

(Suler and Zakia, 2018: 149)

Upon discovering these standardised temperatures, I checked the white balance settings on my Olympus EM1 Mark2. Besides a number of presets (Auto, Sunny, Shadow, Cloudy, Incandescent Fluorescent, Underwater, WB flash, Capture WB) there is also the option to set the colour temperature by specifying the Kelvin number. I will experiment with this in due course.

Colour gamuts (colour space)

“The gamut of any medium for reproducing colors will fall somewhere within the horseshoe space… the gamut of colors that can be reproduced at a particular level of luminance is less than the colors the human eye can see (which is represented by the boundaries of the horseshoe shape)” (Suler and Zakia, 2018: 150) It is noted that “every color reproduction medium has this limitation”

Again, I find this hugely significant for photography, and may go some way towards explaining why many people find it difficult to capture the full glory of, say, a sunset, that accords with their own vision of it. I have also found that many photographers over-compensate for this by increasing the saturation in their images – just a thought!

By reviewing and comparing the gamuts of different colour reproduction systems (C, Y, M, K inks, R, G, B phosphors…) it becomes possible to see the limits to the range of colours that can be reproduced in each medium. I note that different brands of ink, for example, may have a slightly different gamut.

“The colors on a monitor are illuminant colors, red, green and blue-emitting phosphors. The prints from an inkjet printer or press printer are surface colors reflected and not absorbed by the cyan, magenta, yellow and black colorants.” (Suler and Zakia, 2018: 150)

These distinctions and the terminology used to describe them are totally new to me, but I fully appreciate their importance to photography and the presentation of photographs. It has helped me to understand why a photograph on a screen may look different (in colour) to the printed version of the photograph. Indeed, I tried an experiment – I uploaded an image on my iPad and placed it side by side with a commercially printed version of the ‘same’ image. There is a marked colour difference:

A further dimension to this issue is that monitors and printers will have different colour gamuts.

Other colour spaces (gamuts) include Adobe sRGB (red), sRGB (blue), and NTSC (yellow):

“The color space for Adobe extends further into the green and cyan area, which means that greens and cyans will be more saturated, more intense. The NTSC (National Television Systems Committee in yellow) has a colour space that is similar to Adobe.” (Suler and Zakia, 2018: 152)

“The sRGB color space was designed for the web. The s stands for standard and the size if its colour space approximates that of most device screens. Although it is relatively smaller than aRGB (a for Adobe it is large enough for most color applications. The aRGB color space, however, covers more of the colors that can be produced on a printer using C, M, Y, K inks.” (Suler and Zakia, 2018: 152)

Again – very important and interesting – looking at my camera’s colour options, I can choose between sRGB and aRGB (Adobe) when shooting.

Suler and Zakia go on to ask whether aRGB is better than sRGB for printer use – the very question that sprung to my mind! The answer, such as it is… is…. it depends…. on:

• the printer
• the inks
• the printing paper

“If one is using a high-quality printer capable of reproducing colors outside the sRGB color space, aRGB is the better choice, especially for greens and cyans. However, there are other factors to consider if the print is to come close to what is seen on the monitor screen.

Transferring color information from the camera to the final print requires a color profile, a set of data that describes how each component – camera, RAW converter, computer, monitor, Photoshop workspace, and printer – will handle the colour space. Printing inks and paper must also be considered. All the separate components must work harmoniously together to create a high-quality color print.” (Suler and Zakia, 2018: 150)

So, there is more to colour than meets the eye! So, so many things to consider!

References

Suler, J. and Zakia, R. D. (2018) Perception and imaging: photography as a way of seeing. (5th ed.) New York: Routeledge

Munsell Color. (2020) The Munsell Color Tree At http://www.munsell.com/color-blog/color-tree/ (Accessed 24/10/20)

SMC468 Graphic Design For Education (2020) The chromaticity diagram At http://www.youtube.com/watch?v=O0nYJ0Mjx10 (Accessed 24/10/20)