Create a still-life arrangement that includes the colours red, yellow, green and blue. Also include a piece of grey card. Convert the taken image into five black and white copies and process each version using the different colour digital sliders in your processing software to mimic the effects of coloured filters.
Filters can be used in photography, either as an actual coloured filter in front of the camera lens or as a digital filter applied during post-processing i.e. photoshop. A colour filter works by letting through its own colour but absorbs its opposite, complementary, colour. For example, a blue filter allows all blue light, such as from a blue sky, through it but blocks yellow light. Intermediate colours are affected relatively; violet passes through fairly well, but yellow-green is mainly blocked. Filters are used in colour photography but have a deeper effect when used in the conversion of black and white images.
This exercise was fairly straightforward. I arranged a still life that included red, yellow, green and blue and also the grey card in the top corner. I then used photoshop to convert the image into black and white, and then applied the necessary filters. None of the brightness settings were altered as i wanted the images to simply be converted to the necessary colour filter effect. In hindsight this may have resulted in the effects not being as prominent, but i did not want to alter any levels other than the colour.
Converted to black and white:
The only real difference with the yellow filter in comparison to the standard converted image is that the yellow (lemon) is slightly brighter. This is expected as the yellow filter allows yellow to pass through, while blocking its opposite colour – blue. Therefore the blue background appears very dark, almost black.
The red filter has again brightened the yellow but also the red (radishes) which is to be expected. The green cucumber has darkened substantially as green is blocked through the red filter. Blue is also considered to be an opposite of red – therefore the blue background is still appearing very dark.
The green filter absorbs the green of the cucumber therefore brightening its appearance, while the red radishes have darkened to the point that they are barely visable.
This image highlights the effect of filters extremely well. The blue filter has completely blocked out the yellow leaving the lemon to appear black. The blue background has lightened significantly giving a very different overall feel to the image.
Use of colour filters in black and white images can have a major effect on the tones and there are certain ‘rules’ for each colour of filter. By learning which filter blocks out or allows specific colours to pass through helps the photographer to compose and shoot an image that should work well in black and white. The use of filters can give the photographer more control in regards to deliberately making an object stand out in a black and white image by careful filter selection.
The results of this exercise may have been slightly more noticeable had I played around with other levels such as brightness and contrast, but as i mentioned before i wanted the colour filter to be the only alteration.