I want to known the difference in color measuring between L*, a* b* and L*, C* h*
For my experiment, I used L*, a* b* for measuring the color values of gelatin powder. Anyway, reviewer comments that "With respect to color analysis, instead of showing L*, a* and b* parameters to characterize the samples color, I suggested to present as L*, chroma coordinate C* and hue angle. The C* parameter is interesting because it shows saturation color, and hue angle expresses the object color."
So, what is the best way to respond?? Thanks
Jamal,
I cannot add to Benedict and Miguel responses -- both provided great answers. My intent is to just add a couple of comments. Calculating Hue angle can be tricky and Miguel's clearly highlights the issue with his formulas. The reviewer is right on in asking about for C and H. My years of experience in measuring meat color would suggest that you do not get the "full story" of your color measurements if you only compare samples/treatments using L*a*b* as C and H can give you a more "global" perspective of your experimental variables. From a practical point you likely will find 1 or 2 of these measurements will be very good for characterizing your gelatin samples.
Here is a guide that might serve as a good reference: The "AMSA Meat Color Measurement Guidelines". Its a free download from the American Meat Science Association at: http//www.meatscience.org Then search for the guide.
Best of luck with your work!
Hey Jamal,
the Lhc colour space is the same colour space as Lab but uses other coordinates. Lab uses the polar coordinates a and b while Lhc includes the cylinder coordinates h and c.
You can convert the polar coordinates a and b mathematically into the cylinder coordinates h and c with a specific equation which you can find - for example - on wikipedia.
I prefer the L*, Chroma (C*) and Hue (*h) polar coordinates, may be because I visualize the polar coordinates better than rectangular ones. I suppose that some people prefers the L*, a* and b* (rectangular) coordinates. Like Benedit wrote, the two scales are fully equivalent,
Chroma=(a*^2+b*^2)^(1/2)
Hue=arctan(|b*|/|a*|) (if a*>0 and b*>0)
Hue=180-arctan(|b*|/|a*|) (if a*0)
Hue=180+arctan(|b*|/|a*|) (if a*
Jamal,
I cannot add to Benedict and Miguel responses -- both provided great answers. My intent is to just add a couple of comments. Calculating Hue angle can be tricky and Miguel's clearly highlights the issue with his formulas. The reviewer is right on in asking about for C and H. My years of experience in measuring meat color would suggest that you do not get the "full story" of your color measurements if you only compare samples/treatments using L*a*b* as C and H can give you a more "global" perspective of your experimental variables. From a practical point you likely will find 1 or 2 of these measurements will be very good for characterizing your gelatin samples.
Here is a guide that might serve as a good reference: The "AMSA Meat Color Measurement Guidelines". Its a free download from the American Meat Science Association at: http//www.meatscience.org Then search for the guide.
Best of luck with your work!
I concur with the above responses and simply offer one more reference source. Konica Minolta and their equipment are used widely, worldwide for several applications across several disciplines. Not an advertisement, just a fact. Search: http://www.konicaminolta.com/instruments/knowledge/color/pdf/color_communication.pdf for their bulletin titled "Precise Color Communication: Color Control From Perception to Instrumentation". This wonderful manual explains much more about color than you probably want to read, and the formulae already provided are therein too. Note, making the negative values absolute values or reversing the tangent to arctangent is required, as already denoted by Miguel Angel García-Alvarado. Good luck!
John C. Beaulieu
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