A photon is a photon. All photons travel at the speed of light. Whether the photon comes from an HPS or an LED is and the height is of no consequence. The density of the light affects the number of photons per second for a given area.
In horticulture the number of photons, in µmoles, per square meter per second is the standard measurement. Plants use photons regardless of the energy the photon carries and this is why a quantum measurement is used.
200 high quality 3 watt (200 x 1amp x 3.0v) will produce more photons per second than a 1000W HPS. This was proven by Cree with their Horticulture Reference Design compared to a Gavita Pro HPS 1000W.
Photon output can be produced and measured in many ways. There are LED fixtures (e.g. Heliospectra) that do a better job than HPS. Higher photon output, adjustable spectrum, and better uniformity. High price tag, lower operating costs. Superior to HPS.
Then there are the cheap inefficient fixtures with inefficient LEDs, inefficient power supplies, poor thermal management, and poor uniformity. Low price tag with high operating costs. Inferior to HPS.
When a vendor compares their photon output to HPS in watts, they are more often than not, lying. Example 600W HPS equivalence with 120 five watt LEDs.
There are those that evaluate a fixture by the wall watt draw. These cheap fixtures can draw twice the current and output half the photons as another fixture with the same wall watt draw. The efficiency of the LEDs 30% cheap Chinese - 80% Cree XP-3G) and power supply range from 70% Cheap Chinese to 95% Mean Well. As long as buyers use wall watts to compare the low efficiency parts will continue to be used.
This fixture below has 132 of the cheap inefficient LEDs so called 5 watt. But the watt rating of an LED does not equal forward voltage x current. White and blue have are about 3v and red and yellow have about 2v forward voltages. The estimated total forward voltage here is 320v. The LEDs are powered by four 70v-90v, 500mA LED drivers. Divide 320v by 4 = 80v. But the brightness of a quality Cree or Lumiled white is many times brighter.
When I see a board that looks like this, it's just a waste of electricity.
This board has four columns of white LEDs (the yellow phosphor LEDs).
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The brightness of the LED is very dim compared to top tier LEDs.
This board could NEVER compete with HPS.
Notice the photo of white LEDs below this one was taken with the same camera at 500mA.
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The white above and below, are night and day. 200 of the LEDs below would beat HPS.
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Cheap LED drivers
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