Thomas, The usual nomenclature for this space is L*C*h Deltah is not the same as DeltaH* (or DeltaH*ab as it is sometimes referred to in regards to the CIELAB color difference). Deltah is the difference in angle while DeltaH* is the contribution of the angle difference to the total error, and is equal, for the CIELAB color difference (DeltaE*ab) to: DeltaH*ab = SQRT(DeltaE*ab ^2 - DeltaL* ^2 - DeltaC*ab ^2) Danny www.babelcolor.com -----Message d'origine----- De : Colorsync-users [mailto:colorsync-users-bounces+dpascale=babelcolor.com@lists.apple.com] De la part de Matthew Finlay Envoyé : 13 décembre 2017 00:00 À : Thomas Richard; colorsync-users@lists.apple.com Objet : RE: Delta H Calculations Thanks Thomas, So just to clarify, Am I correct in assuming from the below that DeltaH is the absolute value between each H value in the LCH color space? -----Original Message----- From: Thomas Richard [mailto:trichard@richard-ebv.de] Sent: Wednesday, December 13, 2017 12:48 PM To: colorsync-users@lists.apple.com; Matthew Finlay <mfinlay@sb-media.com.au> Subject: Re: Delta H Calculations Hello Matt, look at Bruce Lindblooms homepage: http://www.brucelindbloom.com/Eqn_Lab_to_LCH.html MfG Thomas _______________________________________________