730nm used change photochrome help??

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/

Do you understand my question? You need 12hrs of darkness or 13. If you don't have a far red light. Which takes the 2hrs away needed to switch from pfr to pr. With a 730nm far red you use it and it takes 5 mins instead of 2hrs to put your plant to sleep. You need 2hrs without you for it to be fully asleep. It explains it here better. It gives you an extended time so basically it's like a 26hr day if that makes sense. Your plants are getting a 1.50hr extra time aa it only takes 5-10m to put your plant to sleep if you use your far red to put to bed. So, I'm a bit lost in your response tbh.

how much far red do you want in proportion to everything else? i'mnot sure.. 14/10 will potentially be fine at any points. The general line in the sand for causing flower phase is 10 hous of uninterrupted darkness. It is not univesal, however. So, you may end up confusing a plant and causing a revege at some point.. no idea how often. 13/11 is safer... if you need to squeeze a little more DLI into a dayily cycle that'll give you 8% more than 12/12. Relative to your environement, there's a maximum amount of light your plant can receive per day before it starts to become a hinderance. Daily Light Integral is best way to understand it because size of garden and hours of light are already part of how the value is calculated, so it is relative. 40 DLI in one gaden is 40DLI is every garden no matter the size or light cycle. it's simply counting moles of photons hitting the plant. variation due to genetics in addition to temps, RH and CO2 levels, the last being the limiting factor in most contexts. 35-40DLI for ambient co2 is about as how as you can go... can push those boundaries but won't push far and may even need to dial back a hair. 50-60dli depending on environemental controls with 1200-1300ppm co2. tighter you contro temps and RH (specifically local to each and every leaf), you'll never be able to push 60+DLI without damaging plant. So... are you not providign enough light on curent light schedule? that'd be the only reason to increase to 14/10 or 13/11... try 14/10 at your own risk. might work but probably run into a plant or 2 eventualyl that re-veges... and if you can do it 1-2 weeks after "flip" then you can do it at flip... it's a hormone response that requires a minimum amount of time of uninterrupted darkness.... if you want to give more, wait for last week or so of bloom and you can probably give 18/6 without consequences, but again... should be providing enough over 12/12 or 13/11 in the first place... or if shooting for maximum, already giving that uppwer tier relative to co2 levels.