Some more information regarding YPF (yield photon flux). Two parts here, first a description and second the data that is used as weight factors.
Yield Photon Flux is a metric utilized in horticultural lighting that is based on the PAR/nm and the ability of a plant to utilize the light energy at each wavelength to drive photosynthesis. In essence, it shows how efficiently a plant is able to utilize the light across the spectrum. The generation of this metric is based partially on the original work performed by McCree, et. al.
The following curve is the relative quantum efficiency in plant photosynthesis:
Notice that according to this curve, the red spectra has higher efficiency than the blue. As such, lights with higher amount of red will tend to have higher YPF values.
If we were to capture the spectrum from a light source, in this case sunlight:
And, then overlay the values used to generate PAR (PFD) and YPF, we have the following:
The orange area consists of the values used to generate YPF. These values are the values of the original spectrum multiplied by the relative quantum efficiency (RQE) transfer function.
The dark blue area consists of the values used to generate PAR which is essentially the original spectrum with the ends chunked off.
Notice that YPF extends further into the deep blues and deep reds and that the reds contribute more to the final result.
There are some criticisms regarding YPF. The main criticisms is that the original works used to generate the RQE for plants was that the test used relatively low light levels of less than 200 umols.
For those into numerical analysis, here is the data for RQE where RQE is multiplied by the umols/nm then integrated to produce YPF.