2000

\(\begin{align} &C_1 = \text{hypot}(a_1,b_1)\\ &C_2 = \text{hypot}(a_2,b_2)\\ \\ &\bar{C} = 0.5(C_1+C_2)\\ &G = 0.5\left(1-\sqrt{\dfrac{\bar{C}^7}{\bar{C}^7+25^7}}\right)\\ \\ &a_1' = a_1(1+G)\\ &a_2' = a_2(1+G)\\ \\ &h_1' = \begin{cases} 0&\text{if }b_1 = 0\text{ and }a_1' = 0\\ \text{arctan2}(b_1,a_1') \bmod 360&\text{else} \end{cases}\\ &h_2' = \begin{cases} 0&\text{if }b_2 = 0\text{ and }a_2' = 0\\ \text{arctan2}(b_2,a_2') \bmod 360&\text{else} \end{cases}\\ \\ &C_1' = \text{hypot}(a_1',b_1)\\ &C_2' = \text{hypot}(a_2',b_2)\\ \\ &\bar{C}' = 0.5\left(C_1'+C_2'\right)\\ &\bar{H}' = \begin{cases} h_1'+h_2'&\text{if }C_1'C_2' = 0\\ 0.5(h_1'+h_2')&\text{if }|h_2'-h_1'| \le 180\\ 0.5(h_1'+h_2'+360)&\text{if }|h_2'-h_1'| \gt 180\text{ and }h_1'+h_2' \lt 360\\ 0.5(h_1'+h_2'-360)&\text{if }|h_2'-h_1'| \gt 180\text{ and }h_1'+h_2' \ge 360 \end{cases}\\ \\ &\Delta h' = \begin{cases} 0&\text{if }C_1'C_2' = 0\\ h_2'-h_1'&\text{if }|h_2'-h_1'| \le 180\\ h_2'-h_1'+360&\text{if }|h_2'-h_1'| \lt -180\\ h_2'-h_2'-360&\text{if }|h_2'-h_1'| \gt 180 \end{cases}\\ &\bar{L}' = 0.5(L_1+L_2)\\ &T = 1-0.17\cos\left(\bar{H}'-30\right)+0.24\cos\left(2\bar{H}'\right)+0.32\cos\left(3\bar{H}'+6\right)-0.20\cos\left(4\bar{H}'-63\right)\\ &R_C = 2\sqrt{\dfrac{\bar{C}'^7}{\bar{C}'^7+25^7}}\\ &\Delta\theta = 30\exp\left(-\left(\dfrac{\bar{H}'-275}{25}\right)^2\right)\\ \\ &\Delta L' = L_2-L_1\\ &\Delta C' = C_2-C_1\\ &\Delta H' = 2\sqrt{C_1'C_2'}\sin(0.5\Delta h')\\ &K_L = \begin{cases} 2&\text{textiles}\\ 1&\text{default} \end{cases}\\ &K_C = 1\\ &K_H = 1\\ &S_L = 1+\dfrac{0.015\left(\bar{L}'-50\right)^2}{\sqrt{20+\left(\bar{L}'-50\right)^2}}\\ &S_C = 1+0.045\bar{C}'\\ &S_H = 1+0.015\bar{C}'T\\ &R_T = -R_C\sin(2\Delta\theta)\\ \\ &\Delta E = \sqrt{ \left(\dfrac{\Delta L'}{K_LS_L}\right)^2+ \left(\dfrac{\Delta C'}{K_CS_C}\right)^2+ \left(\dfrac{\Delta H'}{K_HS_H}\right)^2+ R_T\left(\dfrac{\Delta C'}{K_CS_C}\right) \left(\dfrac{\Delta H'}{K_HS_H}\right)} \end{align}\)