Development Pages
Dave
COLLIER

Experiments with Colour Filters
Select picture
or specify image url apply
will be converted to 500px × 375px

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, In the late 19th and early 20th century there were the Biocolour process, Kinecolour and early Technicolor, all used red and green filters onto black-and-white film, re-projected through red and green filters to create something approaching full colour on screen.
And colour films made by Claude Friese-Greene in the 1920s, on YouTube. Friese-Greene used the Biocolour process
Can we simulate that on the computer monitor? This page starts with a colour photo and runs it through two filters of different colours, the results of which it converts to greyscale. Then it re-projects’ that greyscale image through the two colour filters to obtain a full colour additive mix.
It kind of works – notice that on the final additive mix the blues do come out blue, despite being made up solely of red and green – and it will work much better as I hone the colour brightness formulas and filters, I hope.
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 =
The colour-filtered pictures converted to greyscale.
There are different formulas for converting colour to greyscale (which we do in order to simulate black-and-white film). These have different effects:
like PS
W3C YIQ
YIQ squared
CIE XYZ
XYZ squared
Lgt’ness
Average
brightness weighted

inverse gamma
gamma
: exponent

(Explanation of each formula at foot of page.)
 Positive Negative Positive Negative + % % + % % Brighten Darken by value by percent by inverse % Brighten Darken by value by percent by inverse % average brightness 0 average brightness 0 inverse % = darker shades affected more than lighter
Greyscale image projected through the [ opposing ] [ same ] filter.
 % %