Objective: To demonstrate the effects of using coloured filters with black and white images. This will be achieved digitally by carrying out a black and white conversion of a coloured image and applying red, yellow blue and green filters digitally using imaging software. There is a 18% grey card included in the image (bottom left corner) to ensure that the exposure is neutral.
Original Image: 6495 1/125s f22 60mm softboxes left and right at 45º
Straight B&W conversion. I don't have a version of photoshop which includes a straight forward B&W conversion. I used Capture NX2 which has two sliders; a filter hue calibrated in ° of the colour circle and a filter strength slider calibrated in %. I have shown the effect and the slider positions above each image. I was unable to reduce the effect of colours other than the selected one. To show any appreciable differentiation, each filter effect needed to be full strength.
Default: Hue 60° strength 40% (the application uses these settings on applying Black and white conversion.)
Yellow: 60° Strength 100%
Red: 360° Strength 100%
Blue:240° Strength 100%
Green: 90° Strength 100%
The effects of the filters can be clearly seen here although there are some differences in the tones compared to the examples in the course book. It would be interesting to know which method, film or digital, was used to produce those images. The most striking difference is with the blue filter. The Wratten 47 has rendered the blue to white, whereas in the example above, the blue is at its lightest but nowhere near white. It is also interesting to note that the 18% grey card has remained consistent in its tone throughtout.