A lot of things that can be done are not of great value to actually do. Plants can adapt well to a wide range of light intensities and light spectra. So, there is little to be gained by pursuing an accurate measure of just the light that is most effective for plants. On the other hand, if you enjoy the science involved, and that is part of the pleasure this hobby provides to you, then there is no reason not to seek such light measurements. This is a hobby, so enjoyment is the goal.