Re: Assessing bird colouration

Posted by Robert Dougherty on Dec 20, 2010; 4:08pm
URL: http://imagej.273.s1.nabble.com/Re-Assessing-bird-colouration-tp3686131p3686132.html

On Dec 20, 2010, at 12:14 AM, Ross Ahmed wrote:
>
> So could anybody provide a step-by-step method, which would produce results
> comparable with those of Ericson, for photographing the bird (my camera is a
> Canon 40D) and analysing the photos in Image J (or any other program)?
> Robert Dougherty in particular hinted that this may be possible.
>
>

Ross,

Here are some possible suggestions based on the discussion so far.  

1. Put your hands on a spectrometer and a tungsten-halogen light, etc., and duplicate  Ericson's approach.  Measure a spectrogram and calculate the CIELab color parameters a, b, and L. Compare these with Ericson's tables.

2. Look at the link Gabriel sent: http://imagejdocu.tudor.lu/doku.php?id=plugin:color:chart_white_balance:start. Get one of the color charts and photograph the bird and the chart at the same time with your Canon. (Same illumination, same camera settings, maybe in the same exposure.)  Use the Yves Vander Haeghen's macro to adjust the image to be "closer to the sRGB color space." Convert to CIELab using Fiji using the Image>Color menu that Johannes mentioned.  Compare with Ericson's tables as in method 1.

Method 1 is probably more accurate, as Gabriel has pointed out, because the spectrometer is a scientific instrument and the camera is not.  In either case, I'd suggest some validation testing. Perhaps measure hoopoes of known origin?

Bob

Robert Dougherty, Ph.D.
President, OptiNav, Inc.
1414 127th Place NE #106
Bellevue, WA 98005
[phone]
FAX [phone]
www.optinav.com
[hidden email]