How much light do you really need?

ComputerSaysNo said:

Watts/area says nothing about the hanging height or the actual time the light is turned on.

I can hang a 2000W light 2 meters above a 0.25 m² grow space and run it for a random amount of time per day. The numbers are meaningless now.

If somebody tells you X Watt per ft², you need to make a lot of assumptions to draw any conclusions from that.

DLI actually gives you an amount of light that reached the plant. The number is so much more informative.

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Bignutes said:

I just don’t have the means to get a par meter.

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jimihendrix1 said:

A Gavita 1700e is meant as a 1:1 replacement for a 1000w HID. i have used the 1000w Hortilux HPS in a 4 x 4 for almost 3 decades. A 1000w HID has been the indistry standard for a 4 x 4 since they came out in 1977-78, ad was known as the Supernova. It was a Metal Halide, and if one wants to get technical, a bulb they used in nuclear subs to grow veggies was the first commercial HID sold on the market, but it was so fragile they wouldnt guarantee it in shipping. The Supernova came out about 6 months after the navy bulb.

The Gavita 1700e is 1700umol, and 645w of Samsung/Osram diodes. The 1000w Hortilux is 1600umol. Close enough for a direct replacement.
So the Gavita 1700e is a direct replacement for an HID that is made for a 4 x 4 area.

At that rate the Gavita is 42.5w Sq/ft, and the 1000w Hortilux is 62.5w sq/ft. That is the formula I use, and will continue to use, and IMHO makes it simple. Trick is for the LED is that one has to use Samsung/Osram diodes.

While w x sq/ft may not be the end all say on the matter, its close enough.

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Gavita CT 1930e LED | Gavita – Retail

Watch how easily STIIIZY and LIIIT Farms replaced their HPS lights with energy-saving CT 1930e LEDs. Download whitepaper Benefits Independent control and optimization to make the most of your…

gavita.com

Larger, more powerful 3.5mm LEDs

• Plus up to 20% energy savings vs. 1000 W Single Ended HPS fixtures (based on average wattage of each fixture)
• The industry’s first and only LED that is a 1:1 HPS replacement
• Impressive 1930 µmol/s output for more crop-loving light at up to 20% energy savings vs. 1000 W DE HPS fixtures (based on average wattage of each fixture)
• Compact design fits seamlessly in HPS layouts, reducing the pain when replacing hundreds at a time
• Broad spectrum designed to deliver the deep blues, hot reds and balanced greens plants need for full-term growth
• Wide, even light distribution that matches HPS light throw while improving coverage for plants on the periphery

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• LEDs for 4' x 4'
• LEDs for 5' x 5'

jimihendrix1 said:

In reality straight from their site they compare the CT1930e to a DE 1000e.

And in your above Gavita ad it also stated the CT1930e has a 20% energy saving over the 1000w DE HPS Fixture.

Better learn to read, and apply reading comprehension.

Energy savings vs. 1000 W DE HPS fixtures (based on average wattage of each fixture)

The Gavita Pro 1700e LED grow light has a lower wattage than one might think, with a 645-watt power draw. This means it can replace a 1000w HP lamp with compromising light intensity and quality.

Best LED Grow Lights of 2021 Comparison & Review Test Using Laboratory Data

• LEDs for 4' x 4'
• LEDs for 5' x 5'

Gavita 1700e wins both size areas.


The Gavita Pro 1700e LED uses over 3,300 diodes while the next closest brand uses slightly over 2,200 diodes.

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calvin.m16 said:

I'll pay a few hundred more bucks a month for electricity than lose a few pounds to LED. I've yet to see a LED grow that tops HPS. Weight isn't everything.

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ComputerSaysNo said:

That's quite a bit of mumbo jumbo coming from somebody who accuses others of putting out "false information".

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calvin.m16 said:

You mad?

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Has said:

If You Can’t Measure It, You Can’t Improve or Manage It.

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Has said:

If You Can’t Measure It, You Can’t Improve or Manage It.
In most cases, this is true, but theory and calculations are also needed. Because simply applying a sensor is not always enough.
The inverse square law works at 100% of a point light source in free space. In optical fiber by 0%. In real boxing, somewhere between them and at different points in different ways.
Let's say you have a growbox 2 * 2 * 6 feet with a Led bar on the entire roof 2 * 2, and its machines and bottom have a reflection of 90%.
If you place the probe 1 foot away from the lamp, it will read eg 1000 micromoles. there is no inverse square law here (unlike point HPS), because the light from neighboring chips is added to the light of an individual chip decreasing according to this law when the sensor decreases. However, it still does not work very well due to the reflection of the walls. There is also no "optical fiber effect" yet, because at this height the reflection from the walls is insignificant. While everything is simple.
Now place the sensor 5 feet from the lamp (1 foot from the bottom). It will probably read about 200. Here the "Fiber Effect" is already starting to work, but then why is the sensor reading so small? When light is reflected from the walls twice, it will remain (0.9 * 0.9 = 0.81), three times 0.73, four times 0.66, and so on. Probably three times is the maximum that happens in the stead, but not sixteen to weaken to 0.2.
This is where the difference between the reflection in the box and the fiber is manifested, and the fact that the loss in the fiber is much less than 0.9 is not the main thing (the number of reflections in the box is not so large). The walls of the box, when reflected, also strongly scatter the light, that is, give it all sorts of directions.
What does the sensor measure? - light falling on it at an angle of 90 radii and light from 0 to 90 multiplied by the cosine of the angle (from 0 to 1). That is, not the whole value, such as a microphone (although most also depend on the direction) or a thermometer. And a small part of the light even comes from below reflected from the bottom.
It's just that the sensor does not catch all the light, as well as the human eye and the camera, and therefore it "works" ideally in these tasks.
Plants catch light in all directions inaccessible to the measurement of the sensor and this should be taken into account. For a complete picture, it is worth at least placing the sensor in the usual horizontal, vertical and inverted position to summarize the readings.

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jimihendrix1 said:

Ive been growing with HID since 1977-78, and have yet to have 1 bulb explode on me. I know they can, but in my personal experience, Ive yet to have on explode, or break. Im always careful not to touch the bulb. and if I do, I wipe ot thoroughly with a clean cotton cloth, and I never foliar feed with the light on, and if I do foliar feed, I always wipe the bulbs down with a clean dry cotton cloth.
I also replace my bulbs every 70 days of veg on 24/7, and every 2 flowering cycles. This is for a single ended 1000w HPS/Hortilux
For a Dual Ended bulb I replace them every 6 months of 24/7, and every year of 12/12.
I think they say a DE bulb retains 90% of its power for a year, but Im not so sure, so I replace them more often.

A SE bulb loses 10% the first month, and then stabilizes.

I never had any fires, or close calls at all. I had a buddy that was in his grow room with no shirt on, and was sweating, and accidently bumped into a 1000w HPS and it exploded. It burned the shit out of him too. Water and HID are a bad mix.

Click to expand...

Has said:

If You Can’t Measure It, You Can’t Improve or Manage It.
In most cases, this is true, but theory and calculations are also needed. Because simply applying a sensor is not always enough.
The inverse square law works at 100% of a point light source in free space. In optical fiber by 0%. In real boxing, somewhere between them and at different points in different ways.
Let's say you have a growbox 2 * 2 * 6 feet with a Led bar on the entire roof 2 * 2, and its machines and bottom have a reflection of 90%.
If you place the probe 1 foot away from the lamp, it will read eg 1000 micromoles. there is no inverse square law here (unlike point HPS), because the light from neighboring chips is added to the light of an individual chip decreasing according to this law when the sensor decreases. However, it still does not work very well due to the reflection of the walls. There is also no "optical fiber effect" yet, because at this height the reflection from the walls is insignificant. While everything is simple.
Now place the sensor 5 feet from the lamp (1 foot from the bottom). It will probably read about 200. Here the "Fiber Effect" is already starting to work, but then why is the sensor reading so small? When light is reflected from the walls twice, it will remain (0.9 * 0.9 = 0.81), three times 0.73, four times 0.66, and so on. Probably three times is the maximum that happens in the stead, but not sixteen to weaken to 0.2.
This is where the difference between the reflection in the box and the fiber is manifested, and the fact that the loss in the fiber is much less than 0.9 is not the main thing (the number of reflections in the box is not so large). The walls of the box, when reflected, also strongly scatter the light, that is, give it all sorts of directions.
What does the sensor measure? - light falling on it at an angle of 90 radii and light from 0 to 90 multiplied by the cosine of the angle (from 0 to 1). That is, not the whole value, such as a microphone (although most also depend on the direction) or a thermometer. And a small part of the light even comes from below reflected from the bottom.
It's just that the sensor does not catch all the light, as well as the human eye and the camera, and therefore it "works" ideally in these tasks.
Plants catch light in all directions inaccessible to the measurement of the sensor and this should be taken into account. For a complete picture, it is worth at least placing the sensor in the usual horizontal, vertical and inverted position to summarize the readings.

Click to expand...

jimihendrix1 said:

Ive been growing with HID since 1977-78, and have yet to have 1 bulb explode on me. I know they can, but in my personal experience, Ive yet to have on explode, or break. Im always careful not to touch the bulb. and if I do, I wipe ot thoroughly with a clean cotton cloth, and I never foliar feed with the light on, and if I do foliar feed, I always wipe the bulbs down with a clean dry cotton cloth.
I also replace my bulbs every 70 days of veg on 24/7, and every 2 flowering cycles. This is for a single ended 1000w HPS/Hortilux
For a Dual Ended bulb I replace them every 6 months of 24/7, and every year of 12/12.
I think they say a DE bulb retains 90% of its power for a year, but Im not so sure, so I replace them more often.

A SE bulb loses 10% the first month, and then stabilizes.

I never had any fires, or close calls at all. I had a buddy that was in his grow room with no shirt on, and was sweating, and accidently bumped into a 1000w HPS and it exploded. It burned the shit out of him too. Water and HID are a bad mix.

Click to expand...