Colours into tones in black-and-white

This exercise gave us an insight into how colours affect tones in black-and-white photography. It is often said that colour in a photograph may distract from the content and tonal qualities. In order to produce a pleasing black-and-white photo it helps to have an understanding of how you can influence the tonal range of an image by using either filters on a film camera or post processing with software if using a digital camera.

Light & filters
A filter will only let through wavelengths of light similar to its own colour. Any other colours will be blocked which affects the tone of the image. Objects which are the same colour as the filter will appear lighter than other objects that are not.

In the images below I have used different coloured filter effects in Photoshop to mimic the classic black-and-white filters Yellow, Red, Blue & Green. It is interesting to note that the yellow item in the photograph comes through quite strongly with the Yellow, Red & Green filters. The Blue filter appears to hold back most of the colours. Note that the grey background is pretty un-affected though.

This information will be useful when trying to pre-determine how a shot might appear in black-and-white after some work in an image editing package.