Flux ratio f₂/f₁ plotted against log(Age), for all isochrones (red lines), compared to interferometric flux ratios at the same wavelength (blue lines). The upper panel shows the flux ratio at 1.65 μm, while the lower panel shows the flux ratio at 2.2 μm – the central wavelengths for the H and K bands, respectively. The lighter-shaded areas illustrate the uncertainty on each quantity.