VL and RL relations color‐coded by Hubble types: combined I‐band sample (left), SCII K‐band sample (right; the latter is discussed in § 2.4). The gray dashed lines show the 2 σ scatter of the VL and RL relations for the full I‐ and K‐band samples. At I band, ﹩R=R_{d}﹩, the disk scale length; at K band, we used ﹩R=R_{e}﹩, the effective radius of the galaxy supplied by 2MASS. The VL relation shows, on average, that earlier type spirals rotate faster than later types at a given luminosity. The RL relation depends strongly on morphology with earlier types showing a steeper (~constant surface brightness) slope.