Make a still life photo of objects made up of red, yellow, green and blue colours. Include a grey card in the photo. For a digital version of this exercise convert the image to grayscale in Photoshop using the Image > Adjustments > Black and White option. Create five monochrome versions of the photo. For the neutral, no filter version just accept the default settings for the sliders. I could then choose to either use the sliders to control the brightness for the respective versions, or choose the appropriate preset filter. I chose to go with the preset filter route and created photos with a red, green, yellow and blue filter.
For this exercise I wanted to use objects with bright chromas, but not finding anything suitable at home I delved into the stationery closet at work and found these brightly coloured micro binder clips and quickly proceeded to shoot the images before the day got underway. I just roughly grouped the coloured clips together in their respective colours on a sheet of white paper and put my grey card behind. The grey card is not in sharp focus, but that probably doesn’t matter for the sake of this exercise. Unfortunately I had to shoot at a high ISO as I didn’t have a tripod at work.
I also realised during this exercise that while up until now I have been using the RYB colour wheel, I would have to refer to the RGB one (known as the additive primaries) for this exercise as this is what the software uses. The only post-processing that has been done is just the Image > Adjustments > Black and White and then the selection of the different colour filters. I think my grey card has remained consistent throughout the application of the different filters.
The first step was to take the image into Photoshop and then add a black-white layer adjustment to it. This can be seen in fig 2. No colour adjustments have been made. The default settings can be seen in fig 03. As can be seen there is no difference between the green and red tones once converted to black-and-white.
I then took the control image and applied a red filter adjustment layer to it (fig 4). The adjustment settings can be seen in fig 05. The red clips are now quite a lot brighter and so are the yellow ones. The green and blue clips are about the same intensity of shade. The red filter has actually blocked a lot of the light of the blue and green clips.
Next I applied a yellow filter to the control image (fig 06). Adjustments settings can be seen in fig 07. While the tones for the yellow and red clips remained the same as those when the red filter was used, the tones for the blue and green clips show more distinction and it is clear that they are different colours. This is probably to the fact that the yellow filter has a lighter green value (40) than the red filter (-10).
The following filter that was applied was the green filter (fig 08) with the adjustment settings in fig 09. The green filter adds more depth to the red clips, while brightening the green clips. The yellow and blue clips remain the same.
Fig 10 and 11 show the image for the blue filter and settings respectively. The blue filter cuts all values for red, yellow and green rendering the yellow and red clips a solid black. The green clips, however, are a tad brighter than the blue and yellow ones, even though the value is at 0. This is probably due to the fact that the clips are painted with a glossy paint (and paint is a pigment, not light) and therefore, the colour green would contain blue (blue and yellow make green), green being the only secondary colour in the image (according to the RYB colour wheel).
What I have realized while doing this exercise is that while the camera and software use the RGB colour wheel, the objects photographed are created with the RYB colour wheel and this will affect tones when a photo is converted to black-and-white. I also did some rough sketches to work out the colour distribution of each filter according to the filter layer adjustment settings and in each filter the complementary opposite colour is zeroed out. The colour composition of the filters are also analogous as can be seen in my rough sketch.
Freeman, Michael (2007). The Photographer’s Eye: Composition and design for Better Digital Photos. Lewes, England: The Ilex Press.
Prakel, David (2009). Basics Photography 06: Working in Black & White. Lausanne, Switzerland: AVA Publishing SA.