This table is adapted from @Montgomerie2006 and lists all spectral descriptors that are computed by the summary function in pavo.

Color variable Names used Formula Reference
Brightness Total brightness, total reflectance, spectral intensity $B_1=B_T=\int_{\lambda_{min}}^{\lambda_{max}} R_i = \sum_{\lambda_{min}}^{\lambda_{max}} R_i$ @Andersson1999,@Andersson2002,@Ornborg2002,@Andersson1998,@Smiseth2001,@Saks2003,@Pryke2001,@Shawkey2003
Mean brightness $B_2=\frac{\sum_{\lambda_{min}}^{\lambda_{max}} R_i}{n_w}=\frac{B_1}{n_w}$ @Delhey2003,@Siefferman2005
Intensity $B_3=R_{max}$ @Andersson1999,@Keyser2000,@Keyser1999
Saturation Chroma, reflectance ratio, spectral purity $S_1= \frac{\sum_{\lambda_a}^{\lambda_b} R_i}{\sum_{\lambda_{min}}^{\lambda_{max}} R_i} = \frac{\sum_{\lambda_a}^{\lambda_b} R_i}{B_1}$ @Ornborg2002,@Andersson1998,@Smiseth2001,@Siefferman2005,@Peters2004,@Shawkey2003
Spectral saturation $S_2 = \frac{R_{max}}{R_{min}}$ @Andersson1999
Chroma $S_3 = \frac{\sum_{\lambda_{R_{max}}-50}^{\lambda_{R_{max}}+50} R_i}{B_1}$ @Shawkey2003
Spectral purity $S_4 = \lvert b\text{max}_{neg}\lvert$ @Andersson1999
Chroma $S_5=\sqrt{(B_r-B_g)^2+(B_y-B_b)^2}$ @Saks2003
Constrast, amplitude $S_6 = R_{max} - R_{min}$ @Keyser2000,@Keyser1999
Spectral saturation $S_7 = \frac{\left(\sum_{\lambda_{320}}^{\lambda_{R_{mid}}} R_i - \sum_{\lambda_{R_{mid}}}^{\lambda_{700}} R_i\right)}{B_1}$ @Andersson2002,@Pryke2001
Chroma $S_8=\frac{R_{max}-R_{min}}{B_2}$ @Andersson2002,@Smiseth2001
Carotenoid chroma $S_9=\frac{R_{\lambda_{700}}-R_{\lambda_{450}}}{R_{\lambda_{700}}}$ @Peters2004
Peaky chroma $S_{10}=\lvert b\text{max}_{neg} \lvert\frac{R_{max}-R_{min}}{B_2}$ @Ornborg2002
Hue Hue, peak wavelength, spectral location $H_1=\lambda_{R_{max}}$ @Andersson1999,@Ornborg2002,@Andersson1998,@Delhey2003,@Smiseth2001,@Keyser2000,@Siefferman2005,@Shawkey2003
Hue $H_2 = \lambda_{b\text{max}_{neg}}$ @Andersson1998,@Smiseth2001
Hue $H_3 = \lambda_{R_{mid}}$ @Andersson2002,@Smiseth2001,@Pryke2001
Hue $H_4 = \arctan\left(\frac{B_y-B_b}{B_r-B_g}\right)$ @Saks2003
Hue $H_5 = \lambda_{b\text{max}_{pos}}$ @Keyser1999
• $$R_i$$: percentage (or proportional) reflectance at the $i$th wavelength
• $$\lambda_{max}$$, $$\lambda_{min}$$: upper and lower (respectively) limits of wavelengths
• $$n_w$$: number of wavelength intervals used to calculate $$B_T$$
• $$R_{max}$$, $$R_{min}$$: maximum and minimum percent reflectances, respectively
• $$\lambda_{R_{max}}$$: wavelength at maximum reflectance
• $$b\text{max}_{neg}$$, $$b\text{max}_{pos}$$: maximum negative and positive slopes of reflectance curve in a region of interest
• $$B_r$$, $$B_y$$, $$B_g$$, $$B_b$$: total brightness in red ($$r=625-700\,nm$$), yellow ($$y=550-625\,nm$$), green ($$g=475-550\,nm$$) and blue ($$b=400-475\,nm$$) segments of the spectrum
• $$\lambda_{R_{mid}}$$: wavelength at the reflectance midpoint between $$R_{max}$$ and $$R_{min}$$ (i.e., $$\frac{R_{max}+R_{min}}{2}$$)