Re: Colorimetric Parameters
Posted by
Michael Schmid on
Feb 18, 2015; 9:33am
URL: http://imagej.273.s1.nabble.com/Colorimetric-Parameters-tp5011588p5011654.html
Hi Rita,
you will need a plugin to convert to L a b colors, e.g. one of these:
http://imagejdocu.tudor.lu/doku.php?id=plugin:color:conversions_between_rgb_color_space_and_lab_color_space:start http://rsb.info.nih.gov/ij/plugins/color-transforms.html http://rsb.info.nih.gov/ij/plugins/color-space-converter.htmlYou have to make sure that the illumination has a color rendering index close to 100% (no fluorescent light, also most LEDs have poor CRI) and the camera's color balance is set correctly, i.e., a standard gray card should appear with neutral color.
http://en.wikipedia.org/wiki/Color_rendering_index http://en.wikipedia.org/wiki/Color_balanceNevertheless, you should not expect absolute accuracy, only consistent results for one camera type and illumination source. The spectral sensitivities of the R, G, B pixels of different camera types are not the same, so you may get slightly different values with different camera types. You will also get somewhat different results for light sources with different color temperature.
Michael
________________________________________________________________
On Feb 13, 2015, at 12:20, Rita Goncalves wrote:
> Hello everyone,
>
> I've found this program ImageJ just a few days ago, so I have no experience in it and my question should be easy to answer.
>
> I am studying the coloration of fruits and I need to know its exact value of colorimetric parameters, I mean the L*, a* and b*. Is this possible? All that you can tell me about color would be very usefull.
>
> Thank you very much.
>
> Rita
>
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