Jim Gollan @ OCA Art of Photography: Control the strength of colour (3.1)

Requirement

5 photographs

Purpose

To show how colour brightness changes with exposure, whereby under-exposure darkens hue

Technical learning

Monochrome images, with their currency of contrast and brightness, help focus attention on line, shapes, textures and tones
However, colour - as a design element - works differently and often produces a strong response, emotional as well as physical

3 qualities of colour

Hue

Essential quality of how we name colour e.g. red, blue, etc.
Primary colours are 'irreducible', i.e. they cannot be created from mixing other colours.
2 basic systems: reflective (or painters') and transmitted (light).
Painters' primaries are Red, Yellow and Blue. Light primaries are Red, Green and Blue. (the Red and Blue of each system are different)
Secondary colours are created by mixing 2 primaries in equal amounts.
In the painter's system: Green = Blue and Yellow, Orange = Red and Yellow, Violet = Blue and Red.

Saturation

Purity or intensity of a colour from grey.
At full saturation a colour contains no grey at all.
Conversely, at low saturation the colour would be mostly grey.

From desaturated to fully saturated

Brightness

Degree to which black (shade) or white (tint) is mixed with the hue at a given saturation.
At one end of the scale is pure white, at the other pure black.
Judge brightness from ‘very dark’ (shade) through ‘average’ to ‘very bright’ (tint)

Tints of yellow

Shades of yellow

Note - charts sourced from Designing for the Web by Mark Boulton

http://designingfortheweb.co.uk/book/index.php

Saturation interacting with brightness

The chart below shows how for a red hue of the car body part extreme changes in saturation and brightness interact.
I created this chart from the photograph of a red car, shot in RAW and adjusted the saturation and lightness in Photoshop.

Central image: The (impure) red car body part as shot by me
Min Saturation: Min Brightness: Desaturation towards a grey tone, darkened by lowering brightness (adding black) to produce a near black. If the car body was pure red, the result would have been black
Min Saturation: Max Brightness: Desaturation towards a grey tone, lightened by increasing bightness (adding white) to produce pink. If the car body was pure red, the result would have been white.
Max Saturation: Min Brightness: Full saturation of red content, darkened by lowering brightness (adding black) to produce a deep maroon
Max Saturation: Max Brightness: Full saturation of red content, lightened by increasing brightness (adding white) to a day glow red

Control over saturation - exposure

Several techniques give you control over colour at the time of shooting – one of the most basic is saturation

Project and review

Find a strong colour, e.g. a painted door. Fill the frame with the coloured subject. Take 5 bracketed exposures: average +/- 0.5 and 1.0 stops. The underexposure reduces the brightness of the image and conversely overexposure increases it.

Leaf in close up