Colours into tones in black-and-white

In this exercise, colours are completely desaturated in order to see how changing the relative brightness of yellow, red and green can affect the tonality of a black and white. It is designed to demonstrate that colour relationships affect black and white images as well as colour images.

I used a similar set up as the example in the notes - peppers are an obvious choice for demonstrating the required effect, a piece of broccoli providing some green.

f22; 1/60 ISO 400

This image was then imported in the Photoshop Raw Convertor and the basic convert to grayscale applied. The resultant neutral image is:

A succession of filters were then applied using the colour sliders in the Raw Convertor. I kept a record of the exact amount of adjustment as follows:

Filter	Red slider	Yellow slider	Green slider	Blue slider
Natural	0	0	0	0
Red	+70	-40	-100	-100
Yellow	-100	+100	-100	-100
Green	-100	-40	+100	-100
Blue	-100	-40	-100	+100

The resultant images are set out in the order above:

red filter

yellow filter

green filter

blue filter

There is evidently a greater degree of contrast when filters are applied as by definition one colour is exaggerated at the expenses of the others. This is especially noticeable with the yellow filter; not only is the yellow pepper almost burnt out by the filter but the red one becomes much darker. The blue filter affects the background.

Two main learning outcomes from this exercise:

1) colour filters can be used to good effect in black and white images;

2)  need to look at effect of changing filter on all the colours, not just the most obvious one.