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Experiments with Colour Filters
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This page is in the experimental stage. It takes a colour photo, runs it through two filters of different colours, the results of which it converts to greyscale. Then ‘re-projects’ that greyscale image through the two colour filters to obtain a full colour additive mix. It kind of works, and it will work much better the more I hone the colour brightness formulas and filters. A complex topic that I’m in the process of writing up. The experiment is inspired by Experiments in Colour Vision by Edwin Land from 1959 (Land’s paper here). Land was not the first to demonstrate the effect of creating coloured images from black-and-white film taken through filters, for example see some of the colour films made by Claude Friese-Greene in the 1920s, on YouTube. Friese-Greene used the Biocolour process, there was also Kinecolour and early Technicolor, all red and green filters to full colour from black and white film.
You need to scroll down the page to see the progress of the experiment, or collape the sections to see parts at a time.
Adjust filter colour and opacity (%) of the FIRST filter. Adjust filter colour and opacity (%) of the SECOND filter.
Brightness value of first filter =
Brightness value of second filter =
Automatic complementary colour Automatic brightness equivalence
The colour-filtered pictures converted to greyscale. Positive Negative
There are different formulas for converting colour to greyscale (which we do in order to simulate black-and-white film). These have different effects:
Explanation of each formula at foot of page.
Greyscale image projected through the [ opposing ] [ same ] filter.
Light Source Colour and Intensity Light Source Colour and Intensity
Additive mix of opposing-filtered.
True Additive
Alternate pixels
Random pixels
Each panel shows the colour photo converted to greyscale according to one of five formulas for converting to brightness.
STW* is the formula devised by me, and discussed in detail on Readable Text in Colour – STW*.
W3C YIQ is the YIQ formula recommended by the W3C and discussed on Holes in the W3C Colour Readability Guidelines.
The formulas for other three: CIE XYZ, Lightness and Average, can be found on Puzzling Greys.

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