The trick now was going to be to take these images with a modern digital camera and avoid the camera re-balancing the colour back to a "nominal" normal. Underwater I use red filters as red light is almost completely absorbed by 10m of water. Adding a red filter and white balancing the camera on a grey card, reduces the influence of the other colours, bringing red back into the image, but at the cost of a couple of stops. In this exercise I would need to do the opposite.
I set up the still life in a small light tent using a couple of strip lights from IKEA as my light sources, one to the right and one directly above to create some soft shadow. I then photographed a grey card illuminated by the lights and used this image to establish a manual white balance, which I then used for all proceeding shots.
Here is the first photograph of the arrangement as a colour image, with my grey card as a reference. In the following images I have done no post processing at all other than a conversion from RAW to JPG and reduction in size to 1024 points wide. The camera was set on aperture priority at f/16 and ISO 100. I also used a 50mm prime to avoid any creep in the focal length which would have happened on a zoom lens as I swapped out the filters. In each photo I have simply indicated the length of the exposure.
Colour, 2 seconds
The next shot I took was exactly the same, but with the camera now switched to monochrome (actually this had to be done in Lightroom, as RAW does not care about B&W versus Colour).
No Filter, 2 seconds
In the next image I have added the blue filter to the lens
Blue, 8 seconds
With the blue filter the first change that is apparent is that we have lost 2 stops of light. Other than that the blue background has lightened as have the green objects. Moving onto the Green filter
Green, 15 seconds
With Green the light loss is now 3 stops and the Red items have darkened perceptibly, whilst the Green items are much lighter. Next Red!
Red, 15 seconds
Once again a 3 stop loss of light, but this time a dramatic change in the colours, the Red peppers and tomatoes are almost white. What is also noticeable is that the Yellow objects show less colour change, but that might be because in monochrome they start as a very light shade of grey. My final filter is Yellow
Yellow, 3 seconds
Only a 1/2 stop change in exposure an overall reduction in contrast, but no dramatic changes as seen with the red filter.
Very interesting exercise and perhaps a glimmer of interest in black and white, especially with the use of filters.
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