Pink Rozay

An expensive spectroradiometer is not needed to achieve this this. Apogee has cheaper ePAR meters that can detect the 730nm wavelength now. I just got one and will be measuring the ratio in my light bar very soon.

It comes down the to the ratio of Red photons to Far-Red photons(R:FR). This ratio matters much more than just the intensity of the far-red light alone. Normal daytime R:FR is 1.3:1 (1.3%) and is applied throughout veg. Sunrise and Sunset have an increase R:FR at about 0.6 (0.6%) for about 30 minutes each.

  “The R:FR ratio of direct sunlight is about 1.3 during most of the day, but it approaches 0.6 or so during twilight when the atmosphere preferentially   scatters blue light and the sky turns yellow and red. This only lasts for half an hour or less, but it is important because plants use these changes to   synchronize their internal circadian clocks both with the 24-hour day and the seasons. This involves a burst of gene expression activity that is  controlled by phytochrome.”    “High-pressure sodium (HPS) lamps, on the other hand, have an R:FR ratio of about 4.8, metal halide lamps have R:FR ratios varying from 2.6 to 3.4  and white light LEDs (regardless of color temperature) have R:FR ratios varying from 3.6 to 4.0. Various fluorescent lamps have R:FR ratios varying  from 5.5 to 13.0 and above.”    “Far-Red Lighting and the Phytochromes”, Ian Ashdown, Maximum Yield,   www.maximumyield.com/far-red-lighting-and-the-phytochromes/2/17443     The University of Utah Crop Physiology Lab uses a R:FR that is lower than normal daytime ratios (1.5:1 or 1.5%) to minimize the effects of stem elongation in their experiments. Below is an example from one about phosphorus overfeeding vs harvest yields:
    “The fraction of far-red photons (700 to 750 nm) was 1.5%. Because the far-red fraction was low, the classic PPFD and the ePPFD were within 1.5%   of each other”  "Sustainable Cannabis Nutrition: Elevated root-zone phosphorus significantly increases leachate P and does not improve yield or quality"   F. Mitchell Westmorelan, Bruce Bugbee, www.frontiersin.org/articles/10.3389/fpls.2022.1015652/full

This actually explains how you use far red to change the photochrone time and it gives you extra time to to have your plant under the light. Its proven. Anyways. Thanks for your reply https://sprouthousesupply.com/product/hlg-flowering-initiator-far-red-bulb/