Tuesday 20 May 2014

Colour - Birder's Colour Pallet Rev. 1.0

It came as a surprise to discover that the internet lacks any standard colour pallet and appropriate colour nomenclature for birders.  The nearest thing to an ideal nomenclature for our needs is Ridgway's Color Standards and Color Nomenclature (1912).  Sadly, this standard is all but lost and, as of yet, it cannot be digitised properly (see HERE).

sRGB is a colour standard in itself (albeit somewhat limited in terms of our full appreciation of all colours).  With a bit of effort surely there is enough good material online from which to construct a useful colour pallet.  After a few failed attempts I gave up trying to reconstruct Ridgway's colour standard in sRGB colour space but, like a dog with a bone, I have persisted and the result of my efforts is presented below.

First a bit more rationale.  It was while working on the colour profile methodology (HERE) that the realisation struck me that Ridgway and similar colour standards are not suited at all for field birding and field-based digital image work.  Though the means exists to cater for changing ambient light temperature and some in-camera variables (X-rite colorchecker passport and grey card), the variability of ambient light intensity, camera exposure accuracy, and camera dynamic range all continue to play havoc with accurate colour capture from nature.  

The Eureka Moment!

Why bother with luminance in our chosen colour pallet?  Ridgway's plates  consist of just 36 hues and just 5 saturation settings.  That is just 180 colours to start with!  The rest (nearly 1,000 colours) are simply the same 180 colours at different luminance settings.  Ridgway saw a benefit to having these in his standard in that they might allow for an appreciation of the pattern of natural wear and fading in nature.  While this is no doubt of value under ideal, neutral, diffuse lighting in a museum or study setting, it is all but impossible to study and capture these things accurately in nature.  My philosophy is simple, let's do the best we can with what we have and discard anything too cumbersome or likely to discourage the average birder.


I have maximized the scope and simplicity of sRGB by selecting 10% of its hues, each hue spaced evenly apart, i.e. 24 hues, starting at hue 0 (red) followed by hue 10, 20, 30 etc.  Next I selected a number of saturation increments, 3 is enough I think - 100%, 66% and 33% saturation (note: 0% saturation = grey scale).  I now have a grid consisting of just 72 colours, evenly spaced across sRGB colour space.

Finally, the hard, but a most enjoyable part, I have researched the web to find and name each if these 72 colours based on some of the most recognisable colour nomenclature used in birding.  And here is the result.

How this standard works is quite simple.  First lets assume a photograph of a bird is already properly calibrated (DNG profile and white balance steps are accurately completed - see HERE).  Lets take a patch of colour from the photo (using the colour sampling technique - see HERE).  Correctly naming this colour swatch using this standard simply requires it's hue, saturation and luminance values.  The naming protocol needs to be ironed out - suggestions welcome.  Right now I am going with a double-barrel combination of two colours if the colour swatch happens to fall right in the middle.  If it is reasonably close to just one of the named colours (say within 3 hue increments and 10 saturation increments) it will be given that name.  Luminance can either be ignored (eg. in the case of a badly over or under-exposed image) or it might be referred to in broad terms, i.e. "light" or "dark".   

Armed with that information, here are a couple of examples.  The colour swatch below is from a desert species.  It falls roughly midway between cinnamon and ochre so the colour is cinnamon-ochre.  It also has a very high luminance. The colour is therefore called Light Cinnamon-Ochre (alternatively Light Tawny-Ochre as both Cinnamon and Tawny are considered interchangeable in this standard).

We have to accept that this is only an approximation but that isn't the main point of the exercise.  We now have a standard to use for discussing and debating colours.  The colour nomenclature is relevant to birding.  The method is easy to use, easily replicated on any computer, and available to everyone.  Last but not least, there is no requirement to calibrate a monitor or even to have proper colour vision to be able to use the method as intended.

Some birds are very aptly named...

I hope it becomes a useful standard and, as always I appreciate feedback.


A bit more clarity added in the posting linked above.

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